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crazyvwvanman
Samba Member
Joined: January 28, 2008
Posts: 9913
Location: Orbiting San Diego
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 Posted: Wed Jul 28, 2021 6:41 pm Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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Electricity can flow either direction in a wire.
Electricity can flow either direction through a resistor.
The 2 resistors are wired to each other at each of their stages.
After you cut the 2.5 black wire to one fan the speed 4 power backfed up through the 1.5 black wire to the resistor for the uncut fan, through the 3rd speed section of that resistor and jumped across to the 3 stage section of the other resistor and down to the other fan motor.
So sure, both fans still turn with speed 4 selected after cutting 1 of the speed 4 wires but 1 fan should be turning slower. since It's power is backfeeding through resistor sections to reach the fan motor.
I mentioned in another thread of yours that the 2 fans are not fed separately and are not isolated from each other.
Mark
| djkeev wrote: |
| dgbeatty wrote: |
| Dave the 2.5mm˛ wire you cut is only used for speed 4. Speeds 1-3 use a 1.5mm˛ black wire. |
Yes I am aware of that.
I figured two wires, one goes to each fan.
Cut one
One fans stops……..
Nope!
They both keep spinning!
It’s haunted!
Dave |
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greebly
Samba Member
Joined: August 27, 2009
Posts: 966
Location: Here and now
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| Posted: Wed Jul 28, 2021 7:12 pm Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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| jimf909 wrote: |
| greebly wrote: |
| I was aware from looking at the wiring diagrams to refrain from running my AC on #3 blower speed as it utilizes the AC relay (#3 pictured below)The AC relay is already tasked with providing power to the compressor clutch. |
| greebly wrote: |
I would forward that fan speed 3 is more dangerous than fan speed 4.
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You sure did make me curious about using fan speed three so I ran the van for about 20 minutes with the a/c on fan speed 3 (the same as yesterday but the fan speed was on 4 yesterday) and the overall temps are considerably lower on speed #3 (in this humble experiment):
- Naturally, the speed #4 relay had the biggest difference dropping from 201 degrees to 132
- The drop in temp for #1, the compressor clutch relay is curious given that it was engaged 100% of the time but I attribute that ti it's neighbor dropping nearly 70 degrees
- The #3 multi-function (and speed 3) relay is hotter as I'm guessing it isn't sharing the load with the #4 relay (?)
- Also as expected, the red wire to relay #2 is also much cooler, possibly dropping out of the danger zone depending on the rating for the insulation.
Given the overall temp drop this reinforces my intent to never use speed #4 and use speed #3 only intermittently (it's noisy and with the plenum removed it isn't often needed).
| djkeev wrote: |
Excellent post!
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Agreed. |
I would agree temps will be generally lower on fan speed three vs fan speed four (except as you have shown on the AC relay). That relay is my concern. A combination of sticky fans and a rad fan that is pulling too much coupled with a slow blow 50 amp fuse ( a perfect storm). I have opened one up, the contacts are not rated for 30 amps. Seperate fusing of the rad fan and compressor clutch would make it safer. |
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jimf909 
Samba Member
Joined: April 03, 2014
Posts: 7455
Location: WA/ID
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| Posted: Wed Jul 28, 2021 8:01 pm Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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| greebly wrote: |
Seperate fusing of the rad fan and compressor clutch would make it safer. |
Thanks.
It does seem that separating the circuits makes sense. dgbeatty has mentioned the rad fan several times.
| dgbeatty wrote: |
Dave, there are a few problems with the design/implementation of the rear mounted A/C. In no particular order.
1. The low speed radiator fan is controlled by the overloaded multi function relay. Solution: add a relay under the dash to remove the load. This in itself will reduce the heat and some of the wiring damage.
2. Loose the strip fuse replacing it with a MIDI fuse. Same for the 2 x 20 ATOs.
3. Increase the 4mm˛ wiring with 6mm˛ as was done in SA.
4. A very careful study of the diagrams will reveal errors. Whereas the blowers are shown to have seperate connections for each blower in truth both blowers share combined connectors thus pushing a 40amp load thru 6.3mm terminals, bad juju. Solution: seperate into individual connectors as designed.
There is more |
_________________
- Jim
| Abscate wrote: |
Do not get killed, do not kill others.
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Current: 1990 Westy Camper - Bostig RG4, 2wd, manual trans w/Peloquin, NAHT high-top, 280 ah LFP battery, 160 watts solar, Flash Silver, seam rust, bondo, etc., etc.
Past: 1985 Westy Camper - 1.9 wbx, 2wd, manual trans, Merian Brown, (sold after 17 years to Northwesty who converted it to a Syncro). |
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djkeev
Samba Moderator
Joined: September 30, 2007
Posts: 32561
Location: Reading Pennsylvania
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| Posted: Thu Jul 29, 2021 3:23 am Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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I'll just write it off as electrical VooDoo.
Sitting here staring at the wiring diagram.
If you have two fans being powered by one power source, I see no way to prevent this feed back short of using one way diodes.
As I mentioned earlier, the Evaporator assembly electrics don't seem to be problematic.
The fires seem to happen at the relays.
Admittedly my fault sample is rather small.
Mine was clearly the Fan Speed #4 relay the burst into flame.
The picture posted earlier isn't so clear but it seems to be the left side of the clutch relay.
The fan relay certainly shows heat signs.
On both of these fires the worrisome hot multifunction A/C relay seems unscathed.
The #4 relay? I understand why it got hot and burned, heavy draw on a light relay.
The A/C clutch relay? The A/C clutch just doesn't take that much power. Why the heat?
I figure if you remove 1/2 (more or less) of the power draw on one feed, the over heating should be lessened.
The screws on the fuse, both ends, gets hot as do the wires attached to them.
Dave
_________________
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greebly
Samba Member
Joined: August 27, 2009
Posts: 966
Location: Here and now
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| Posted: Thu Jul 29, 2021 5:18 am Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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| The seperation of the power circuit of the fans are at their grounds via individual 20 amp fuses. The easiest solution is to replace the original 40 amp high speed fan relay with a 70 amp relay. This is something even the most electrically challenged novice can and should do. |
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jimf909
Samba Member
Joined: April 03, 2014
Posts: 7455
Location: WA/ID
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| Posted: Thu Jul 29, 2021 7:21 am Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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| djkeev wrote: |
Mine was clearly the Fan Speed #4 relay the burst into flame.
The #4 relay? I understand why it got hot and burned, heavy draw on a light relay.
The A/C clutch relay? The A/C clutch just doesn't take that much power. Why the heat?
Dave |
In my measurements, the speed 4 relay and the wire from the bus to the relay had the highest temps, 200 degrees, when I ran the blower on speed 4.
To me, the 20 amp fuses look like the center of the conflagration in the other photo of the fire, not the clutch relay. I didn't post a photo but they ran hot too, esp. on speed #4.
My take is that there are a number of overloaded components packed together in a tight space and the risk of fire increases with any component operating outside of design parameters. Add a system with low charge and a driver cranking it up to 4 and problems ensue.
I inspected the blower speed 4 relay and the contact was black. I'm sure it's not operating as designed and is likely running hotter than it was back in 1990.
_________________
- Jim
| Abscate wrote: |
Do not get killed, do not kill others.
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Current: 1990 Westy Camper - Bostig RG4, 2wd, manual trans w/Peloquin, NAHT high-top, 280 ah LFP battery, 160 watts solar, Flash Silver, seam rust, bondo, etc., etc.
Past: 1985 Westy Camper - 1.9 wbx, 2wd, manual trans, Merian Brown, (sold after 17 years to Northwesty who converted it to a Syncro). |
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greebly
Samba Member
Joined: August 27, 2009
Posts: 966
Location: Here and now
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| Posted: Thu Jul 29, 2021 8:05 am Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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| jimf909 wrote: |
To me, the 20 amp fuses look like the center of the conflagration in the other photo of the fire, not the clutch relay. I didn't post a photo but they ran hot too, esp. on speed #4.
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I believe you are right It does appear that the 20 amp fuses were the location of the start of the fire.
| jimf909 wrote: |
| My take is that there are a number of overloaded components packed together in a tight space and the risk of fire increases with any component operating outside of design parameters. Add a system with low charge and a driver cranking it up to 4 and problems ensue. |
Agreed. I was looking at 120mm 12volt fans today. |
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djkeev
Samba Moderator
Joined: September 30, 2007
Posts: 32561
Location: Reading Pennsylvania
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kamzcab86
Samba Moderator
Joined: July 26, 2008
Posts: 7915
Location: Arizona
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| Posted: Thu Jul 29, 2021 10:06 am Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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| djkeev wrote: |
I find this diagnosis of the fuses starting the fire slightly disconcerting!
All my life going back to the 1950’s I’ve been told to
FUSE IT! …. PREVENT FIRES!!
Now you are telling me …….
YOU IDIOT! …… THAT FUSE YOU PUT IN STARTED THE FIRE!!!!
Color me confused
Why didn’t the fuse blow?
I understand oversized fuses not being effective but……
Dave |
I've always wondered this myself.
Google brought up this:
https://rennlist.com/forums/928-forum/612742-fuse-melting-but-not-blowing-2.html
In short:
Over-amperage = blown fuse
Overheating from resistance = melted fuse and/or holder
_________________
~Kamz 
1986 Cabriolet: www.Cabby-Info.com
 1990 Vanagon Westfalia: Old Blue's Blog
2016 Golf GTI S
"Real knowledge is to know the extent of one's ignorance." - 孔子 |
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bobbyblack
Samba Member
Joined: May 21, 2015
Posts: 4348
Location: United States, Iowa
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| Posted: Thu Jul 29, 2021 10:24 am Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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The 20A fuses I found in my D pillar were original looking, yellow, with an exposed wire fusable link. These were hot to the touch when I first worked on my wires back there. I scrubbed up the ground post/rings, and changed to more modern looking 20A fuses. Testing again, I found the temps way lower by just doing that much. Then I forged ahead and put in a PWM. I only get about 1/2 way up the PWM dial achieving the same results that the #3 setting gave. Again, tested temp in the wires. WAY lower. Why trust/use the stock resistors when a much more efficient modern device is available?
YouTube for italjohn's front blower PWM mod, and SyncroJael's rear blowers PWM mods here on thesamba. They inspired mine.
-bobby
_________________
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greebly
Samba Member
Joined: August 27, 2009
Posts: 966
Location: Here and now
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| Posted: Thu Jul 29, 2021 11:49 am Post subject: Re: AC wiring issues and improvements. |
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| crazyvwvanman wrote: |
Since you have come this far and have the tools, why not measure the currents at the fuses for each of the 2 fan motors individually?
That will tell you what the true load is on the 3rd speed relay contact and the 4th speed relay.
I'd be curious what the voltage changes at the fan motors are after some wiring rework so I'd first measure and record those values for each of the 4 fan speeds before making any wiring changes.
Measuring the current at each of the 2 fan fuses might also give you an idea of whether the fans are in similar states or if one has a problem developing.
Mark |
It's a 100° today but I went out and took some measurements. First a picture of the discoloration of the connector from the ground connections between the 20 amp fuses and the blowers. I believe this may have been the culprit in the fire photo. It got toasty.
The grounds from the connector are brown and black. For identification purposes I am going to call Brown AC Blower fan 1 and black will be blower 2.
Blower 1 ground current:
Fan speed 1) 2.2 amps
Fan speed 2) 3.6 amps
Fan speed 3) 7.9 amps
Fan speed 4) 13 amps
Blower 2 ground current:
Fan speed 1) 1.8 amp
Fan speed 2) 3.5 amps
Fan speed 3) 7.6 amps
Fan Speed 4) 12.2 amps
Current to source feed of AC relay clutch circuit: 2.2 amps
I need to add that my son who was recording Current readings while I switched the AC on and off noted that the clutch drew an intitial surge of 20 amps before it stabilized to 2.2 amps.
Current to source feed of AC Radiator fan circuit 13.1 amps. I did not record the starting surge of the radiator fan, but I would assume it's hefty as well.
Voltages at main supply wire terminal of fuse ( Keep in mind I have a 1.8T with a larger alternator)
fan position 1) 13,5 vdc
fan speed 2) 13.4 vdc
fan speed 3) 13 vdc
fan speed 4) 13.1 vdc.
In retrospect I should have obtained a baseline at the alternator itself as a reference. Another day perhaps.
I have concluded that I will be eliminating that connector and using some heavy duty splices. eliminating the connector that provides positive power to the blowers as well with something more robust and capable of handling the current. Unfortunately the space does not easily accomodate a fan other than 50 mm. Another point to ponder, My AC relay is marked 25 A maximum. |
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jimf909
Samba Member
Joined: April 03, 2014
Posts: 7455
Location: WA/ID
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| Posted: Thu Jul 29, 2021 6:04 pm Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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Back in June, 2017 I was driving from NE AZ to Phoenix on one of those crazy days when runways were buckling and people were frying eggs on the sidewalks. It was a long drive and when I arrived in Phoenix and stopped at a gas station I noticed a small fire at the fuse box near my leg had just started (yikes!). I opened the door, blew the fire out and saw that it was the #1 30 amp radiator fan fuse. I've since cleaned most of the fuses...but not those 20 amp blower motor fuses. They're next (I didn't know they existed until a few weeks ago).
Maybe "Replace your fuel lines!" SHould become "Clean your fuses!"
| kamzcab86 wrote: |
| djkeev wrote: |
I find this diagnosis of the fuses starting the fire slightly disconcerting!
All my life going back to the 1950’s I’ve been told to
FUSE IT! …. PREVENT FIRES!!
Now you are telling me …….
YOU IDIOT! …… THAT FUSE YOU PUT IN STARTED THE FIRE!!!!
Color me confused
Why didn’t the fuse blow?
I understand oversized fuses not being effective but……
Dave |
I've always wondered this myself.
Google brought up this:
https://rennlist.com/forums/928-forum/612742-fuse-melting-but-not-blowing-2.html
In short:
Over-amperage = blown fuse
Overheating from resistance = melted fuse and/or holder |
_________________
- Jim
| Abscate wrote: |
Do not get killed, do not kill others.
|
Current: 1990 Westy Camper - Bostig RG4, 2wd, manual trans w/Peloquin, NAHT high-top, 280 ah LFP battery, 160 watts solar, Flash Silver, seam rust, bondo, etc., etc.
Past: 1985 Westy Camper - 1.9 wbx, 2wd, manual trans, Merian Brown, (sold after 17 years to Northwesty who converted it to a Syncro). |
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djkeev
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Joined: September 30, 2007
Posts: 32561
Location: Reading Pennsylvania
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dgbeatty
Samba Member
Joined: October 26, 2006
Posts: 702
Location: Sacramento
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| Posted: Sat Jul 31, 2021 1:00 pm Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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A/C wiring
1. The 6.0mm2 wiring is rated for 50amp continuous in free air. It is derated to 35amp continuous as configured in rear A/C Vanagons. It must be replaced with 8.5mm2 / 8 awg which is rated for 50amp continuous as installed.
2. The combination A/C relay is overloaded and therefore overheats.
It must have a relay installed underdash to off load the speed 1 radiator fan load.
More on this later.
3. MIDI Fuses
The 50amp strip fuse is insufficient for the task and must be replaced with a 50amp MIDI fuse.
The two 20amp blower fuses would have been okay if phosphor bronze or beryllium terminals had been used instead of brass terminals. The solution is to replace them with two 20amp MIDI fuses and holders.
A note on the blower fuses. You can verify the heat load on these two fuses by installing a 30 thermal circuit breaker. Both circuit breakers will trip open in a few minutes on speed 3. On speed 2 they will trip open within the hour.
4. All of the new ring terminals must be rated for high heat ie nickel plated steel. Crimping is critical for this wiring, a $10 pair of crimpers with not be sufficient. You may choose to additionally solder the terminals but it will not substitute for proper crimping.
5. The radiator fan wiring is insufficient and was redesigned for the South African market. It fixed multiple problems including the damage done to fuse 1 30amp that frequently melts and damages the fuse panel and it off loads the fan load from the A/C relay in the rear. In essence the existing speed 2 relay and associated circuit is rewired to become the new speed 1 relay/fuse etc. The existing wiring is well suited to this task. A new speed 2 relay (40 amp minimum) and fuse are installed. I would very highly recommend that a MIDI fuse be used for this high draw circuit. While you are under the dash replace the strip fuse for speed 3 with a MIDI.
6. Lastly, any wire that is discolored and/or stiff has been overheated and must be replaced. Any wire that does have not shiny copper conductors when stripped must be replaced.
All terminals in high heat / high load positions must be phosphor bronze or beryllium, no exceptions. Just as importantly they must be properly crimped.
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greebly
Samba Member
Joined: August 27, 2009
Posts: 966
Location: Here and now
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| Posted: Sat Jul 31, 2021 1:09 pm Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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I took some measurements today, the first set was before making any changes. The second set I replaced the stage 4 blower relay from the original 40 amp to a 70 amp model. These are the before measurements.
Heat measured after several minutes running blower fan position 4. Measurements were taken with an Ambient temperature of 85°. The old 40 amp relay measured 195° after 5 minutes of operation. See the old style 20 amp fuse on the far left? It disintegrated when trying to remove it. I had to completely remove the fuse holder to get the terminals of the fuse out. One of them had fused
in the pinch connection. finally got it removed and the terminal showed signs of deterioration I will be replacing both of the fuse blocks they are PN/ 161 937 501 for reference.
After cleaning ground connections, fuse connections, the ground and supply blower connectors, replacing steel washers with copper washers, replacing the 20 amp fuses and and applying deoxit to all connection points including the relay terminals, the new 70 amp relay measured 155° a drop of almost 40° Ambient at the time of the reading was 91.4° or app 6° hotter.
I measured the connectors prior to disconnecting , inspecting and treating with deoxit. I am positive that a couple of years ago when I refurbed the AC I inspected these connectors and applied deoxit. I do it to every electrical connection I encounter, if the connection is exterior I will also apply super lube or dielectric grease as well. Shock alert  I saw temps as high as 288° on one side of the source connector to the blower. I witnessed similar temps on the Ground connector.
The connector terminals appeared to be fine, no scorching, or discoloration. The connector bodies themselves display discoloration indicating a major hotspot.
These terminals are 6.3mm spade type and are rated at 20 amps maximum. I would prefer to replace these connectors with a similar model using 7.6mm spades and females ( I already have the terminals) but I have not been able to find any connectors that will accomodate them. After much research I found Anderson SB50 connectors which are rated for 50amps, I may change replace them with the Anderson type connectors.
All of the ring terminals had a patina that I cleaned with sandpaper.
A cleaned teminal and the other prior to cleaning. Notice the small scorch mark on the insulation below the right terminal.
Existing steel washers on both fuse terminals and ground were replaced with larger copper washers.
Here is a picture of the 40 amp relay , if you look you can see discoloration on the terminal above the contact, it was also evident inside the case, note the dark stripe that is the side that corresponded directly with the contacts of the relay. It got warm.
Current measurements before and after: I saw a 51 amp initial surge on the supply which settled down to a constant 44 amps before I made any changes. After changing the relay, the 2 fuses and cleaning all of the associated ring terminals current dropped to 40 amps.
I have ordered new S6-8 lugs which I plan on replacing the ring terminals with, I have a 33 mm thick 12 volt squirrel cage radial fan on order and will be installing the 50 amp thermal breaker below it. I don't want the fan to affect the temperature of the breaker, The fan is rated for 40 cfms and the outlet will be directed at the relay panel. I am ordering extra fuse blocks to install a 15 amp fuse on the radiator low speed feed and a 10 amp fuse on the compressor clutch circuit. |
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greebly
Samba Member
Joined: August 27, 2009
Posts: 966
Location: Here and now
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| Posted: Sat Jul 31, 2021 1:55 pm Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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| dgbeatty wrote: |
A/C wiring
1. The 6.0mm2 wiring is rated for 50amp continuous in free air. It is derated to 35amp continuous as configured in rear A/C Vanagons. It must be replaced with 8.5mm2 / 8 awg which is rated for 50amp continuous as installed.
2. The combination A/C relay is overloaded and therefore overheats.
It must have a relay installed underdash to off load the speed 1 radiator fan load.
More on this later. |
Unloading the low speed fan current from the back sounds like a good idea, but if that is done, why would you need a 50 amp fuse or 8 guage wire? I am drawing 28 amps when using speed 4 on the blowers after the high pressure switch has transfered to relay 5 (radiator speed two) unloading the current demand from the back.
I like the idea of using existing radiator speed two circuit for low speed and rewiring speed two with it's own relay and dedicated fuse. Currently I am seeing 12 to 13 amps draw on low speed, seems the S1 30 amp fuse would need to be reduced. Do you have current draw measurements for rad fan speed two? |
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djkeev
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Joined: September 30, 2007
Posts: 32561
Location: Reading Pennsylvania
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dgbeatty
Samba Member
Joined: October 26, 2006
Posts: 702
Location: Sacramento
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| Posted: Sat Jul 31, 2021 4:38 pm Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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greebly
Your 28 amp measurement is on the very low side, lower than I have ever seen. Might I suggest that you measure long term with a recording ampmeter. In any case it is not good practice to push to 100% utilization. I can only assume VW did/does it for economic reasons. As a note South Africa did not increase the wire sizing during the redesign.
As to reducing the fuse 1 size downward. It is probably a good idea. I would hesitant to go much below 25amp but 20 "should" work. ATO and ATC are "slow blow" fuses by definition but the start up inrush is greater than 20amps.
The steps and materials I outlined are what I offer and I will not do less than a complete repair/modification. Of course others are free to do what they like in the US but remember that a fire extinguisher is useless against a live circuit.
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greebly
Samba Member
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Posts: 966
Location: Here and now
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| Posted: Sat Jul 31, 2021 5:36 pm Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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| I would suggest a 40 amp fuse if the rad fan is removed from the draw. Still suffecient to protect against an abnormal condition but within the capacity of the supply wiring. It would reduce heat on the main fuse and the AC relay. While a worthwhile endeavor it will not address the excessive heat I am seeing at the connectors for the high speed blower circuit. |
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greebly
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