Radiator Fan Blues

[dcaver01]

Can't quite wrap my head around what's going on with my van's radiator fan, hoping someone on here can help. Appreciate any suggestions in advance.

1986 2.1L Westy with Factory A/C 2WD

Radiator Fan does not automatically kick on at any temp.

Low speed only works if I turn on A/C (at any temp) and turns off as soon as A/C is turned off. This is the only time the lower speed comes on.

High speed will come on if I turn on A/C at high temp, between halfway and 3/4 on gauge. It will stay on until temp lowers, AC does not need to stay on. I'll often flip the AC on then off while sitting in traffic to try and trigger the high speed fan if I'm over halfway on the temp gauge.

If I understand correctly, the high speed fan shouldn't be coming on unless the gauge is really high, like 7/8ths or so. I've read where the high speed can be triggered from prolonged AC use due to the compressor heating up the switch. This likely isn't the case for me as I never keep the AC on.


Here's my understanding of the system, and what I've done:

Thermo switch (replaced)
Fuse #1 (replaced)
Second Stage Relay, #5 location (ordered)
Third Stage Relay, Under dash
50 Amp Strip Fuse
Resistor behind headlight

Am I missing any components involved? Does it sound like the new thermo switch could be defective?

Thanks again, I've been reading through previous threads and various articles for a few months dealing with this.

[r.e.wing_fc3s]

if the radiator is badly clogged it can prevent the thermoswitch from operating properly also thermostat.

sounds like you need to remove the lower radiator grill and remove thermo sw. connector jump the terminals to test the fan operation.
_________________
Reference Automotive: NW Washingtons Vanagon Specialist. (360)366-6965. referenceautomotive.com

[dcaver01]

Thanks r.e.wing_fc3s

I can confirm that the fan does work at both speeds. The mechanic jumped it when I brought it in and also, I can get both speeds to work, but only via me triggering it by flipping the AC on/off.

Interesting thought on the radiator being clogged. I could see how that would definitely affect the thermoswitch from doing it's job. I'll check that out to make sure that isn't the culprit.

[Wildthings]

The thermostat and the fan switch need to be matched for the system to work well, and a stock thermostat along with a stock fan switch are not well matched thus the fan can take many minutes of idling at a stop sign in hot weather to come on. This is particularly true in the earlier models, in the later model VW used a lower temperature fan switch, but this still wasn't enough for rigs without AC. You can buy a fan switch with a -75° kick on speed which will cause the fan to kick on early and cycle frequently.

[dcaver01]

I replaced the 40amp #5 slot relay for the second stage of the fan. No change.

I'd like to replace the 70amp relay for the 3rd stage next - any idea on where to find a replacement for this? This is the one up above the fuse panel. Not finding it locally or on any of the online parts stores.

[jberger]

Have you verified the temperature of the coolant?

In my experience it takes a LONG time for the engine to generate enough heat to actually need the fan to come on in stop and go traffic. Forget what the needle position is relative to the LED... the important thing is to find out what the actual ° is.

[dcaver01]

Thanks- i have not verified the coolant temp- what's the best way to do this?

I do think I figured it out. I was putting the lower grill back on and bumped the thermo switch and wouldn't you know it, the high speed fan kicks on and scares the you know what out of me.

I take a look at the thermoswitch, which is new, thinking there's a short. And the third terminal on the female end of the switch is depressed quite a bit - so I'm pretty sure that it was just a bad contact the entire time. I'm going to have to figure out how to repair this, but it's my working theory for now.

[Wildthings]

[crazyvwvanman]

The original has been long ago superseded by a VW 50 amp relay.

New VW/Audi/Porsche part number 8D0951253 , VW/Audi/Porsche relay Type 370

Yes, 50 amps is more than enough.

You can also buy a quality more generic replacement 70 amp version.
Cole-Hersee RA-700112-RN

Mark

[dcaver01]

Thanks Wildthings and crazyvwvanman -

Fan is working at low and high speed now while driving. So it was just the female connector on the thermoswitch. High speed seems to come on more often that I'd think it should, based on my reading it's only supposed to come on when the temp gauge is nearly pegged.

I'll check the actual coolant temps per your advice and see if there's any discrepancy there. But I'm okay with the high speed coming on early and often, probably only issue with it might be killing the fan motor prematurely, but better that than running hot I suppose.

Thanks again for the feedback/advice.