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djkeev
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Joined: September 30, 2007
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Location: Reading Pennsylvania
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kamzcab86
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Joined: July 26, 2008
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Location: Arizona
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 Posted: Wed Jul 28, 2021 7:03 am Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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| greebly wrote: |
| Looks like the replacement fuse has suffered from some heat, the bottom looks slightly warped. |
You're right. From August 2017, when it all was installed:
I did the Westy plenum delete in 2012, so speed 4 hasn't been used since. The A/C as a whole hasn't been used all that much since 2017.🤔
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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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greebly
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| Posted: Wed Jul 28, 2021 7:04 am Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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If you are planning on pulling another source wire from the alternator to power a seperate fused circuit to say the AC relay or remove any load off of the main fuse be aware that the value was calculated probably to blow in the event of any errant currrent draw from the combined components. You may want to downsize the main fuse instead of just relieving some of the load on it. I do not like the design of the system for this reason. The AC relay is overloaded on fan speed 3 and it is the only draw on that 50 amp fuse in fan position 1, 2, or 3. In position 1 and 2 the only loads on the AC are the Compressor clutch and the Rad fan. If the rad decides to pull excessive current on low speed, or the compressor clutch shorts out, the AC relay will get the full 50 amps. The associated wiring will see that 50 amps less what the other component is pulling at the time, say 6 or 7 amps for the clutch and 10 or 11 amps for the fan ) so if the rad fan shorts out it would get at least 43 or 44 amps. If the clutch shorts it may see as much as 40 amps and those wires are 2.5mm2 or 14AWG with a capacity of only 32 amps. Those circuits should be fused seperatly like the blower fans are. Perhaps a 10 or 15 amp fuse for the clutch on the ground side and a 20 amp fuse for the rad fan circuit. The draw on the rad fan motor may require a larger fuse to account for the initial current draw of starting the motor. Measurements are required.
Last edited by greebly on Wed Jul 28, 2021 7:12 am; edited 1 time in total |
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greebly
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| Posted: Wed Jul 28, 2021 7:10 am Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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| kamzcab86 wrote: |
| greebly wrote: |
| Looks like the replacement fuse has suffered from some heat, the bottom looks slightly warped. |
You're right. From August 2017, when it all was installed:
I did the Westy plenum delete in 2012, so speed 4 hasn't been used since. The A/C as a whole hasn't been used all that much since 2017.🤔 |
The wires are very discolored as well with your original picture as a reference. Its admirable that you document everything with photos, I try, but get distracted , or button things up before I realize I failed to take a photo. |
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djkeev
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DuncanS
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| Posted: Wed Jul 28, 2021 7:29 am Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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The component current draws all seem OK as originally designed with the fuse capacity. But what I don't understand is the heat. Motors and resisters and other things doing work get hot, but wires? That can only mean they or their connection terminals are undersized. Relays? A relay is just an electrically operated switch and the coils should not get hot. The relay itself may be getting hot because the contacts are either degraded or undersized.
It seems that just changing the wire sizes and terminal connections along with new higher rated relays should solve all of these problems. I plan to relay even fan speeds 1 and 2 as I've always had trouble with Vanagon switches having a short life cycle. Just had a headlight dimmer stalk switch fail and am switching that to relays as well. Don't like their mechanical latching. Currently my T3 has 17 relays added beyond stock.
Duncan |
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crazyvwvanman
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Location: Orbiting San Diego
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| Posted: Wed Jul 28, 2021 7:34 am Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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Clearly that fuse/wiring upgrade didn't really solve the overheating problem in the stock fuse location for the power feed path.
I wonder if better airflow in that wiring nook isn't called for.
Keep in mind that these fuses are far from precision devices.
A 20 amp fuse may allow several amps more than that for minutes or hours.
Also if a 20 amp fuse is in a hot area it may blow before 20 amps flows through it since it is already hot.
This reality is not hidden, just look at the data sheets for fuses.
They are really meant for severe overload protection, not marginal overload protection.
Mark |
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jimf909 
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| Posted: Wed Jul 28, 2021 7:39 am Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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| djkeev wrote: |
While I understand abandoning the 4th high speed Evaporator fan speed, isn't it kind of silly to do so?
Dave |
It may be silly because I don't understand all the ways this system works. I had no idea the clutch relay operated in the way you explained it, I just assumed it was closed to engage the clutch and open to disengage it. Thanks for that explanation.
But, since I'm seeing high temps at speed four, I rarely (never) use speed four (plenum removed), it seems that eliminating speed four may reduce heat and risk. Keep in mind that I'm an amateur here.
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| Abscate wrote: |
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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
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| Posted: Wed Jul 28, 2021 9:58 am Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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| DuncanS wrote: |
The component current draws all seem OK as originally designed with the fuse capacity.
Duncan |
Keep in mind I serviced the blowers when I refurbished my AC system. My rad fan is new, MY AC relay is new. My AC compressor and clutch had very low miles on them when I put them into sevice. I would say that the current is OK, because almost all the components are in great shape. I would surmise that my blowers are drawing 10 amps each on speed 3 and around 15 amps each on speed 4. YMMV. I will get individual currents when I go back into the system after my parts arrive. I would forward that fan speed 3 is more dangerous than fan speed 4. Another caveat. Avoid chinese relays at all cost. Here is a picture of a chinese AC relay utilizing 22 guage internal wiring that was melting. No way could 22 awg suffice for any of the 3 contacts in the AC relay. This wire was to a contact, not a coil. |
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djkeev
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kamzcab86
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Joined: July 26, 2008
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Location: Arizona
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| Posted: Wed Jul 28, 2021 10:13 am Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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| greebly wrote: |
| The wires are very discolored as well with your original picture as a reference. |
 I didn't even notice that!
Well, I'm now glad this system doesn't hold a charge. The last time I recharged it was about 3 years ago and only used it a couple times afterwards. It hasn't been used since, hence cutting the belt off to reduce engine drag.
_________________
~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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djkeev
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crazyvwvanman
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| Posted: Wed Jul 28, 2021 11:33 am Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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There are 2 "clutch relays" at work here. The main one is part of the A/C multi-relay and works how you expected. It cycles the compressor on/off as deemed by the thermostat.
The solo "clutch relay" whose operation seemed odd is really a more rarely used "emergency cutoff" relay.
It's only job is to detect when the radiator has overheated to the point where the highest speed radiator fan has kicked in and then this "compressor cutoff" relay disables the compressor clutch to reduce the engine load and hopefully allow the cooling system to recover. This condition may seldom occur but that depends on climate and other factors.
Mark
| jimf909 wrote: |
It may be silly because I don't understand all the ways this system works. I had no idea the clutch relay operated in the way you explained it, I just assumed it was closed to engage the clutch and open to disengage it...... |
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kamzcab86
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| Posted: Wed Jul 28, 2021 11:58 am Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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| crazyvwvanman wrote: |
The solo "clutch relay" whose operation seemed odd is really a more rarely used "emergency cutoff" relay.
It's only job is to detect when the radiator has overheated to the point where the highest speed radiator fan has kicked in and then this "compressor cutoff" relay disables the compressor clutch to reduce the engine load and hopefully allow the cooling system to recover. This condition may seldom occur but that depends on climate and other factors.
Mark |
The original relay system did just that coming back from CA a handful of years ago. It had been a long drive and was miserably hot in August when we hit the outskirts of Phoenix. Closed the windows and turned on the A/C. After interchanging onto the 101, the high-speed engaged and the A/C shut off. It did it twice more and that's when I shut the A/C off and opened the windows back up.
_________________
~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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djkeev
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dgbeatty
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| Posted: Wed Jul 28, 2021 5:10 pm Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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Dave the 2.5mm˛ wire you cut is only used for speed 4. Speeds 1-3 use a 1.5mm˛ black wire.
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djkeev
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xclemjustinx
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| Posted: Wed Jul 28, 2021 5:41 pm Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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| So what do you think the bottom line is? Update all the wiring to a bigger gauge? Add more relays? Add a relay box or fuse panel? I'm trying to see how we can come up with a better design. Maybe take a design off what new cars do with their wiring? |
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djkeev
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Joined: September 30, 2007
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Location: Reading Pennsylvania
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| Posted: Wed Jul 28, 2021 6:10 pm Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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| xclemjustinx wrote: |
| So what do you think the bottom line is? Update all the wiring to a bigger gauge? Add more relays? Add a relay box or fuse panel? I'm trying to see how we can come up with a better design. Maybe take a design off what new cars do with their wiring? |
I've been working on my rewire plan.
The issues seem to be on the D pillar, not up in the Evaporator area.
What I see is that the fans are over loading the overall network.
I am going to remove all of the Fan Draw from the factory design.
All four speeds will have their own relay.
All four speeds will get their operating power from a new 2nd power feed wire from the Alternator.
All four fan relays will be activated by the fan switch power feed.
The fan speed switch will no longer power any fan speeds, it will simply activate relays.
The existing power feed will still trigger the A/C clutch, activate the radiator fan and power the thermostat control.
Doing this should cool everything down significantly.
As I mentioned in another thread, I'm toying with adding some vent holes too, I'll cover the holes with speaker grills. Air movement needs to happen in this "D" Pillar!
Dave
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jimf909
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| Posted: Wed Jul 28, 2021 6:40 pm Post subject: Re: Air Conditioning wiring issues and improvements. 89-91 |
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| 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.
_________________
- 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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