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87 Vanagon A/C Electrical Problem
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Phil G
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PostPosted: Wed Oct 01, 2008 2:20 pm    Post subject: 87 Vanagon A/C Electrical Problem Reply with quote

I haven't posted anything for a million years or so, and see about all the names have changed.

If there is anyone here these days with pro level experience with the later Vanagon Air Conditioning (86-on roof air), here's a problem I'm having that I hope someone else has knowledge of. Maybe I can avoid troubleshooting components that I donít need to.

When A/C is switched on, compressor engages, evap cools normally, and evap fan runs normally, pushing cool air through the system. This is with the exception that one of the evap fan speeds does not work (and hasn't for years), but I'm thinking this may only be a 'typical' Vanagon defective switch problem and unrelated to this very recent issue:

After running the A/C for a few minutes there is the smell of melting or burning plastic.

I opened the rear left D-pillar cover to see what I could see since this is the location of pressure switches and fan relays.

I discovered that the 50A 'S0' terminal fused link on the 'additional relay' holder is getting hot enough that it is melting it's terminal base on the load side. After letting the A/C run a bit longer, the fused link finally does its job and fries.

Here's a picture of the components from the factory manual which unfortunately only shows component layout and description. Bentley gives no trouble shooting assistance for the A/C. Components discussed, are in top-right image on page:

Image may have been reduced in size. Click image to view fullscreen.

I uncovered and inspected/tested both relays #15 & #27 which are the left and middle shown. These are the compressor clutch relay and evap fan relays respectively, and they are fine. The remaining large relay on the right is the 'A/C relay'. No tests were performed due to the number of contacts, unknown functions, and that the relay cannot be visually inspected without destroying it (sonic-welded plastic housing).

Additional info:
The two replaceable 20A fuses (S51) for the evap fan that are located in the circuit between the relay and evap fan are fine and do not get hot.

I wish I understood the full function of the 'A/C Relay' so I would know what to look for in a failed function, or failed component that may be causing a near-short / excessive load against the 'S0 fuse'.

Anyone have experience with this trouble?
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tencentlife
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PostPosted: Wed Oct 01, 2008 3:34 pm    Post subject: Reply with quote

I know you have no trouble with the Bentley wiring diagrams; the one for AC is further back in the late vanagon section. The AC relay is just a dual relay arrangement inside, no electronics or anything fancy, and the diagram makes clear what it does.

My first thought on your prob was that the dual rear fans were pulling too much current; it's happened to someone else lately. Could be that they are within but too near their 20A apiece, but the extra load is overtaxing the 50A because it handles other loads in addition to them. Don't have my book handy or I'd take a look to see if that's plausible.
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Captain Pike
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PostPosted: Wed Oct 01, 2008 4:52 pm    Post subject: Reply with quote

I have the same A/C unit in my V. No trouble at all. If you need "good" ohm readings on the components I'll pin it for you in the morning.
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Phil G
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PostPosted: Wed Oct 01, 2008 7:07 pm    Post subject: Reply with quote

And the winner of the cowboy logic award for Best Gut Instinct goes to the man from NM!

Darnit! One of the evap fans is toast, and I can't imagine the other being far behind. I dug out a shunt and began testing current loads. First discovery is that fan speeds #1 & #2 aren't even on the same troubled circuit and are no problem. Fan speeds #3 and #4 are the problem. #3 runs but pulls amps like a 12V soldering Iron. #4 is DOA and 'usedta' work . . only pulls amps like a 12V coffeemaker Laughing

. . . and here I thought I would have the front air box open for the first time way before the dreaded evap housing.

Now I have to go boneyarding for a replacement relay holder since the S0 fuse melted it -
Image may have been reduced in size. Click image to view fullscreen.

And what do you bet this 21 year old plastic will crumble in my hands the minute I touch it?
Image may have been reduced in size. Click image to view fullscreen.

Fortunately the other side was cracked when I got the car years ago and I nut-serted the inner skin of the body to take machine threaded stainless fasteners and a holder made from some Ipe wood I had laying around. Boat guys . . I made left and right, but never got around to serting and installing a left to match . . unfortunately the space available to nut-sert and need to retain access to the factory curtain snap made fastner layout a bit odd, but if you squint it looks great! Laughing
Image may have been reduced in size. Click image to view fullscreen.

Thanks for the thoughts guys, and Bill, than-e for the offer there, but turns out a thermometer won't help a gut-shot mule.

$ .10, your comment "no electronics or anything fancy" struck my funny-bone. During the last 6 months I've been updating my Mercedes 107 climate control system to one 10 years newer involving a different number of switchover valves, a need for an rpm signal from the fuel pump relay that also had to be updated, and a million other issues that are part of turning a 107.025 into a 107.048

Dude, I'm lucky I can still spell my own name. 'No electronics or anything fancy' sounds wonderful . . . wood-burning sounds even better Laughing
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meyervw
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PostPosted: Wed Oct 01, 2008 7:15 pm    Post subject: Reply with quote

Make sure you have a second person handy when you unscrew those 6 screws. Mine hit me hard in the head. I thought it was lighter than it was.
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tencentlife
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PostPosted: Wed Oct 01, 2008 7:25 pm    Post subject: Reply with quote

Well even a blind pig finds an acorn once in awhile.

I looked at the wiring for this later today, and sure enough the 50A in the rear handles current for both evap fans, whose 20A fuses are on their ground legs, incidentally, as well as the clutch pull-in current, plus if I remember right the 1st speed of the rad fan as well. A pretty heavily loaded fuse; 50A seems underrated.

Wow, Phil, I think that's the first unbroken evap housing ear I've ever seen. Even having only one, that wins the prize. Mine are jacked up there with scraps of predrilled angle-steel, y'know, that crappy looking stuff?

Oh, you said your fan 2nd speed never comes on? That is only switched on by the AC high-pressure switch. Your system may have less than a full charge, or the switch might be stuck open.
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Phil G
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PostPosted: Wed Oct 01, 2008 9:06 pm    Post subject: Reply with quote

No, actually during testing, evap fan speeds 1 & 2 work fine so I figure those are one of the fans and 3/4 are the other. I'll have a look at the schematic tomorrow. I'm thinking of just replacing the 50A S0 and not using fan speeds 3 or 4 for now so I can stay focused on boat work for a few weeks. Besides, if I end up having to replace the fans as unrepairable, then new ones are probably pretty pricey. I did the front window motors when I got the van, and by the time I did rubbers and rebuilt the lock motors I had $400 in each door and a ton of labor. Weird that the window motors for the Vanagon cost more than the same thing for 993 Porsche!

Pre-drilled angle thingys? Don't go getting technical on me now, do those come in the 'Gold package' ? Can only blacksmiths buy those? I'm afraid they'd see me for the unworthy wood-butchering chiseler that I am, the minute I bellied up to the counter.
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tencentlife
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PostPosted: Wed Oct 01, 2008 9:19 pm    Post subject: Reply with quote

When I said:
Quote:
Oh, you said your fan 2nd speed never comes on? That is only switched on by the AC high-pressure switch. Your system may have less than a full charge, or the switch might be stuck open.


I meant the radiator fan, of course.

The evap fans both run at the same time, same speed. They have parallel circuits with parallel series resistors. I suppose it's the resistors limiting current so the draw is less on 1 and 2. 4th speed is direct via a relay, 3rd just jumps ahead of the resistor pack as I remember, so the limit on current in those modes is the fan motors.

I beleieve they are the same motors as the heater fans; not sure, though.
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Phil G
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PostPosted: Wed Oct 01, 2008 9:35 pm    Post subject: Reply with quote

Sure, but I never mentioned my radiator fan, which works correctly so I assumed you were referring to the evap fan(s).

No worrys -
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tencentlife
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PostPosted: Wed Oct 01, 2008 10:10 pm    Post subject: Reply with quote

Oh, right, you did say "evap fan", away up there. My bad.
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PostPosted: Wed Oct 01, 2008 10:42 pm    Post subject: Reply with quote

The fan speed switch itself does get burnt contacts. In the 87 and on I do think the actual fan control is the same part as the heater and rear heater switch. So the possibility exists to switch them out for testing. The system does build up more resistance as it ages, contacts get burnt and the spades get corrosion. Lubing the fan motors can give some extended life and lower the draw. In the 86, mine for example, the fans in the AC system are the same as the heater fans. If you have an amp meter you can see what the draw is at the fans, they should be 9-12 amps each if they are in good nick. You may be able to transplant your rear heater fan up there for one of them in the interim. It usually hasn't worked much in its life and is easy to get to.
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Phil G
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PostPosted: Wed Oct 01, 2008 10:55 pm    Post subject: Reply with quote

I'll probably find they've become paddlewheel steamers a few times in their lives and armatures run on bearings of polished rust. How have you been my friend? Nice to see you here abouts Very Happy

Practical idea the rear heater fan Smile) not quite as inovative as a man's leather belt for a T2 fan belt in Baja, but hey . . what could ever be?
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26kick
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PostPosted: Wed Nov 26, 2008 3:00 pm    Post subject: Melting fusable link Reply with quote

Hi guys,

In my '90 Vanagon, I've got this problem as well:

Image may have been reduced in size. Click image to view fullscreen.

Image may have been reduced in size. Click image to view fullscreen.

Image may have been reduced in size. Click image to view fullscreen.

So should I get another one at the junkyard and just aviod fan speeds #3 and 4?

In my case, I think my fans are working. Haven't noticed any issues. Seeing this melting plastic scared me though!

Any input would be great!

Thanks,

Mark
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Terry Kay
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PostPosted: Thu Nov 27, 2008 9:33 am    Post subject: Reply with quote

Believe it or not, there is a difference in the front / rear heater motor's and the AC blower motor's.

Three totally different part number's for the three different applications.

I know that the front heater motor for sure looks identical, but the plastic mounting tabs/ lugs on the bottom are different.

I've got a few AC specific blower motor's, that wern't used hardly at all.
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PostPosted: Thu Nov 27, 2008 9:41 am    Post subject: Reply with quote

Terry,

While I'm sure your correct, the motors, once removed from the plastic enclosures down to the motor and squirrel cage have been interchangeable for me on my 86.
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Terry Kay
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PostPosted: Thu Nov 27, 2008 9:59 am    Post subject: Reply with quote

Yea--the motor's & cages are identical--it's the housing that's are different.
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PostPosted: Wed Dec 03, 2008 7:29 pm    Post subject: Re: Melting fusable link Reply with quote

26kick wrote:
Hi guys,

In my '90 Vanagon, I've got this problem as well:

Image may have been reduced in size. Click image to view fullscreen.

Image may have been reduced in size. Click image to view fullscreen.

Image may have been reduced in size. Click image to view fullscreen.

So should I get another one at the junkyard and just aviod fan speeds #3 and 4?

In my case, I think my fans are working. Haven't noticed any issues. Seeing this melting plastic scared me though!

Any input would be great!

Thanks,

Mark


Where does all this electrical stuff live in the vanagon? I have a 1987 with no ignition and no crank and I'm wondering if this big fuse is blown?
Thanks
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crazyvwvanman
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PostPosted: Wed Dec 03, 2008 7:38 pm    Post subject: Re: Melting fusable link Reply with quote

That stuff lives in the far back corner driver side pillar of 86-91 with factory A/C. It has nothing to do with cranking or ignition.

Mark


aeromech wrote:

Where does all this electrical stuff live in the vanagon? I have a 1987 with no ignition and no crank and I'm wondering if this big fuse is blown?
Thanks
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Tomudell
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PostPosted: Sat Sep 26, 2009 10:16 pm    Post subject: Similar A/C problem Reply with quote

I have a 90 Gl and the A/c system was converted to 134a a few months ago, It was working ok but everyone in a while I though I smelt something like burnt wiring when I would first turn it on. I didn't use it for about 2 months and the when I did it was blowing warm air. I just assumed that there was a leak and needed to be found and recharged. What I noticed is that when I turn the A/C on all fan speeds work great, the fan in front turn on and the clutch on the condensor is not longer coming on. I'm thinking it may be a bad relay - is it #15 or #27 for the clutch relay? Any other suggestions on what I should check?
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26kick
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PostPosted: Sat Jun 12, 2010 2:39 pm    Post subject: Poss solution to melting plastic fuse holder Reply with quote

I was just working on my A/C again and someone at an A/C shop saw my melted plastic. They said, "just run an extra wire (10 guage or so), parallel to the one that's already there (on the melted tab) from the alternator and that'll fix it."

So I did that and the wires still get warm, but not hot. Looks like a fix to me! It certainly can't hurt....if you're careful when you do it. Don't short anything out.

Another consideration that my Vanagon owning buddy warned me about is that while this may fix the hot side of whatever is running, there's still a possible issue on the ground to the fan or whatever. Grounds are notorious for bad connections in our cars. So.....

Do it at your own risk but it seems to have helped in my case.
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