87 Vanagon A/C Electrical Problem

[Farf]

Unfortunitly, yes...Since you know your motors are ok and you have the fan switch accessed you can use an ohm meter and check for continuity to ground at speed 1 wire to ground and speed 2 wire to gtound other than the wire connections the only thing from the switch through the motor and to ground are the resistors. Look at current track roughly 7.5 and 8, speed 2 and 1 respectively at the fan speed switch and follow the path downward through the motors to ground. Disconnect each wire at the switch and put one meter probe on it and the other probe to a good ground if the current path isn't broken you should read continuity on your meter. If not, bad connections or resistors, you will probably have to dig in to find the exact problem.

[Syncro Jael]

[Farf]

Yes, you are correct on your ohm meter test points. It looks like if uou lost one resitor in the bank than both motors would try to run on one resistor, maybe self-imploding. Its possible that your hot relay could be from something in the resistor bank, but I don't know for sure.

[Syncro Jael]

[Syncro Jael]

[Howesight]

The highest speed (4) is switched by a separate relay connected directly to the 50 amp fusible link with no resistor. Look at the wiring diagram on page 2 of this thread. The two resistors consist of stacked resistors that reduce current and voltage the most when current must pass through all three stacked parts of the resistor. Setting the fan switch to "speed 1" forces current to go through all three parts of the resistor and so on. Speed 3 powers a relay inside the AC relay which then connects to terminal 3 in both the series resistors. Speed 4 powers the "evap. fan relay" in the wiring diagram. Speeds 1 and 2 carry the most current through the fan switch because they carry the fan current, not just the signal to the relays, which is what happens for speeds 3 and 4.

In doing my Front AC install, I noted that the pigtail socket at the fan switch can get dodgy, but I was working with a salvaged pigtail.

It looks to me as though there has been a failure in the "evap. series resistor" between points 3 and 4. It is possible that one or both wires have disconnected from their terminals at the resistor. More likely, however, the resistor(s) has failed. I don't recall from your thread whether you were able to service those fans when you refurbished your AC system, but they can draw a lot of power when the bearings are dry.

It might be possible to lower the evaporator enough to reach inside and replace the resistors, without disconnecting the refrigerant lines.

From Dave Vickery's pics, it looks like you might be able to remove a fan from the front of the evaporator cabinet and then gain access to the resistors. Notice how Dave notched his cabinet to allow it to be dropped with the evaporator core still connected?) :

Or maybe access the resistors from the speaker holes through an access hole you cut:

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'86 Syncro Westy SVX

[Syncro Jael]

[Farf]

Speed 3 still needs to go through the resistor banks. I'm thinking that Howesight's take on the problem being between points 3 and 4 on the resistor bank is spot on and a great place to start. I think as long as the resistors are in the airstream you should be ok, someone else may chime in on this.

[Syncro Jael]

[Syncro Jael]

Just to bring this repair to an end.

I guess during all the work on the A/C system and having the cabinet down a couple of times, one of the plastic mounts for one resistor must have broken and was lying sideways on the cabinet bottom. Those things must get extremely hot because it burned a black hole in the wood. It wore through the coating, on the resistor, and I am sure overheat and rubbing on the cabinet made it fail.

The other resistor was still in its mount, but tested bad. So what are the odds that both will fail at the same time? Pretty good odds in my case.

I was thinking of mounting the resistor packs where they would be more accessible, but after seeing how hot it must get I am sure there is a reason the engineers mounted them in the cold air stream of the A/C evaporator cabinet. So I made some new "metal" mounts, insulated the bases, and installed them in the factory locations.

A quick test once all the soldered, heat shrink, connections were made and the van is back to normal.

I now have a set of new relays for the system that are not needed.

So if your A/C evaporator fans will only run on HIGH speed number (4)four only. And you have checked all the appropriate fuses. It will be your resistors that have failed. You can check the continuity of #1 and #2 speeds at the speed switch on the dash. If you do not have continuity, then the resistors have failed for sure.

Thanks to many of you who guided me through this repair.

NOW I HAVE TO GO REINSTALL THE CABINETRY and ROOF PLENUM... But it gave me a chance to re-oil the fan motor bearings again.

Cheers !
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1987 Syncro Westfalia Hightop - NAHT
Subaru EJ25 Forged Frankenmotor, Triple Knob.
Jael = (Mountain Goat)

[blurat]

FYI only. Measured my temp at the fuse with air on High192-209
Installed a length of 12 gauge wire from B+ alt to the load side of the fuse and rechecked, 160-172.
ran for 45 minutes and no problems noted.
This was all after I melted the fuse and block and installed Van Cafe replacement.............while eating an awesome cookie.

Thanks farf for the diagram

[termuehlen]

This is a great thread. Very helpful! I took a look at my '88 Westy A/C wiring and guess what I found:

This seems like a pretty common problem and it makes me wonder how many times this has resulted in an electrical fire. For anyone who has an operating A/C system, this should be tops on their list of things to inspect. It must also get pretty hot back inside this area because the plastic part of my 20Amp fan fuses were also in pretty bad shape:

Here's what things look like following my repair. Now it is time to operate it and see how this goes. I may still add another conductor if I feel this isn't quite enough.

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1988 Westfalia automatic Subaru OBD1
1986 syncro tintop wbx

[Paulbeard]

[Rick Bowman]

Both S51 fuses are blowing when A/C is turned on. Besides fan motors, what else can cause this? (Just hoping it's not the fans)

[Steve Arndt]

Bump. My evap fan quit working today at all settings. Worked perfect before today.

Background I have already replaced the 50A foil fuse with a 50 amp breaker and upgraded the supply wiring to 8 gauge 15 years ago. I haven't taken the panel down. Where should I look first? System was operating perfectly. Went into a store and restarted the system was running on restart minus the evap blower.
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Steve
Steve's 87 Syncro project

[Steve Arndt]