Troubleshooting A/C fan switch

[baltik]

My westy has been sitting for a bit, just decided to get it into fighting shape and am experiencing the following issue:

If I turn the A/C on, A/C clutch engages and radiator fan comes on but the fans in the headbanger do not turn on..

My thought is to start with the fan speed selector switch, which wire should I be testing for current? I also checked fuse s12 and it appears to be in good shape. Anything else to check?

[djkeev]

It would be helpful to know what year Van you have but.......

When you turn on the A/C by rotating the temperature control switch to the right.......
This action
Activates the A/C (if the setting calls for it)
Will turn on the radiator fan if the A/C clutch engages
Will turn on the Evaporator Blower fans.

The blower fan switch gets its power from the thermostat switch.
If the system is powered up, the blower fans should run.

#1 is to check if the blower fans have power, now it would be nice to know what year system you have!

Let's assume you have the newer style with the A/C controls / relays in the LR "D" pillar.

Unscrew the pillar cover to expose the wiring and relays.

You will see three double plugs headed up the "D" pillar to the Evaporator.

One is two brown wires. These wires ground the blower fans.
The two fuses you see protect the blower fans on the ground path.
The ground point is in the pillar as well.
Check the fuses.
Another plug has two wires, if they are just two single wires, that is fan speed #1 & #2.
With the fan speed switch on 1 or 2 one of those wires should be hot.

The other connector is also a double connector but has pairs of wires going to a single wire.
This is speed #3 & #4.
With the switch on 3 or four one of these wires should be hot. Black is speed 4.
Note that the Bentley wiring diagram colors do not always match real life wire colors!

No power at any of these connections?

Fan switch is probably bad or the thermostat switch is not powering the fan switch.

Early models are different than this.
It is always good to put your vehicle in your signature so we can more accurately help you.

Dave
_________________
Stop Dead Photo Links how to post photos

Ghia
http://www.thesamba.com/vw/forum/viewtopic.php?t=392473

Vanagon
http://www.thesamba.com/vw/forum/viewtopic.php?p=6315537#6315537

Beetle
https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert

[DuncanS]

Read 100% of "Air Conditioning wiring issues and improvements. 89-91"
https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight=
You could well have far more serious issues. Consult Bentley. If you don't have one, get it. If you can't read the DIN electrical current path diagrams, study the cliff notes at the beginning of the electrical section and then start.

But you are right. Start with finding out if you have power at the switch.

Then, do you have power on each of the output terminals of the switch. If yes, then your relays or something else is compromised. Speeds 1 and 2 do not use relays, so it will take some time to figure this out. But you will have to do it yourself. There are so many possibilities for the issue that unless you can begin to narrow down the area of failure, answers on this post will just be speculations.

Pull the D pillar liner and inspect everything visually. Anything discolored that may have gotten hot and failed?

Put 12 volts directly to the fans and see if they run, but after checking the switch. You may have mice at home in the fans and blocking them from running. Unlikely, but often the solution to electrical problem proves to be something unlikely.

Always post the year so people can get some handle on the problem as there are many different wiring elements depending on year.

[djkeev]

Ah....... I see you've been down this Road a year ago.

https://www.thesamba.com/vw/forum/viewtopic.php?t=739806&highlight=

Did you ever get it fixed then?

I also see you have an 88 Syncro with a Subaru conversion.

You also have cut and taped wires in the D pillar.......

Never the less, pull the D pillar cover and check for power to the fans, it is easier than pulling the fan switch, which really isn't hard either but doing so stresses connections...... the less you mess with old wires, the better you will be.

Dave
_________________
Stop Dead Photo Links how to post photos

Ghia
http://www.thesamba.com/vw/forum/viewtopic.php?t=392473

Vanagon
http://www.thesamba.com/vw/forum/viewtopic.php?p=6315537#6315537

Beetle
https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert

[baltik]

Thanks Dave! I have a 90 so seems like your advice is dead on. You say that the fans get their power from the AC switch but I could have sworn there was a way to turn on the fans without turning on the AC in the past?

[djkeev]

[DuncanS]

Dave and Mark, AKA crazyvwvanman, are your guys. Listen to what they say, do it and you will be fine.