Mk 3 Golf 92 1.8 Overheats

Are the wires on the thermoswitch the same SIZE as the wires on the fan plug? if they are the same then yes indeed you do have a thermoswitch that can carry the load. I have a 1990 golf schematic with a one speed fan where the current is operated with the thermo switch ( no relay) BUT there is a ' fan After Run ' relay in series and between the switch and the fan. If the switch wires are smaller then you have a relay and probably two for the two speeds.

If you're willing let's try to make the fan work in place.

With the connector on the fan and a gator clip jump clipped to a pin insertted into the high speed fan wire quickly touch and remove the jumper wire to the pos. term of the battery. The idea is to not harm the wiring >much< with the pin yet get the fan to bounce. ( if it was my 92 i'd cut the wire strip a bit both ways twist in a test wire which i'd hold to the pos. batt. term. and let it run ) This will tell you a few things depending on if the fan works.

After you've got the fan working I would flush out your coolant, remove the thermostat and replace rubber seal when you re-attach it. Put a hose pipe into all the pipes till you get clear water. Use the red VW grade coolant, this should be done every 2 yrs. The fan should only cut in when its a really hot day not at this time of year, unless you're in Australia?

I have connected the plug back to the cooling fan, I then bridged the high speed contacts in the thermo switch then connected the +12v battery to the thermo switch bridged contact and the fan runs okay.

I have tried tracing the red wire contact 1 of the thermo switch which supplies +12v to the thermo switch back to the fuse/relay box, I checked fuse 19 which is the feed for the radiator cooling fan but not connected directly to the fuse, have been unable to determine where the red wire goes to and the wiring diagram in the haynes manual is not very helpful as it just shows the red wire going back to the fuse, so for the moment I am stumped.

This is a bit more than what I ask for but still is great to eliminate the fan to wiring failure ( connector rot ) and eliminate the faulty ground, and fan (again). And you are right with the need to find where the big red feed comes from. Since big red isn't on the fuse you have checked . Prolly points back to the module which Dave gave a link (with a picture) to and which your haynes mentions. Or 'big red' goes to some other relay like the ( " rad cool fan after run rly " ) in the 1990 schematic I have here. . >Maybe

The vw dealer closest to me ( > 30 miles ) is always very helpful. They've printed out diagrams for me at the parts window without even buying anything. I am not a regular customer so I> assume< other dealers do the same. The schematic from vw for your car would make your job here much easier. remember no a/c in yours.

Plus if you have the owners manual , there maybe a clue or two in there, maybe even in the " boring warnings section" something like > rad. fan MAY run for 2 minutes even after the car is turned off.

Raylo,

Fuse S19 is a fuseable link under the hood located in a plastic flip- top enclosure just about touching the coolant fill tank (for a 96 Jetta). Could it be loose or corroded?

Also, I have the Haynes and the shop manual (again for the Jetta) and neither show a relay, but the shop manual shows a "coolant fan control module" and it turns the radiator fan on whenever the A/C is on. I cannot find its physical location, but it is in series with the wire connecting the fan high speed to the thermal switch (red/yellow). And it is connected directly to the wire connecting fan low speed to thermal switch (red/black). I believe it opens the high side while applying 12v to the low speed side, resulting in low speed fan operation. Like somebody else said, I bet it's your module or just corrosion on its connections. Looks like the module will need a good connection to 12v too. Sorry I didn't think of it the first time.

PS - The "after-run system" in my manual is shown only for 6 cylinder cars.

Mike

I dropped the fuse/relay box and checked for where the red wire came in to the fuse box which according the diagram was on the fuse but could not find it on the plug going into the 30A position 19, checked another red wire on another plug and checked the continuity was reading nearly a Meg ohm, was not sure this was correct red wire and could not find any problem on the plug connectors or pins in the fuse box.

I then decided that the only way round this was to by pass the problem by cutting the red wire in the harness and then run it via a 30amp fuse to the battery, so I cut it and then put a meter on the cut red wire going back to the thermo switch and so getting nearly a meg ohm in resistance so problem back towards the thermo switch, the harness runs under the battery box (shelf) which I was unable to remove as nuts holding rusted up, managed to pull the cable from under the battery shelf and the resistance changed going up/down, pulled enough cable through to discover a crack in the insulation as I examined the wire it broke and there was alot of corrosion present (very green), hey presto found the fault just need to piece out the wires and make good.

Thanks for all of your help

Ray

Ray

Congrats on finding the problem. It makes me wonder why the wire failed there ? maybe bouncing on the batt. shelf? I sometimes use rtv silicone as a mount / cushion in places were I think rubbing might be a problem down the road , on wires and hoses.

Hmmm I think I mentioned checking those wires around the battery in my first or second reply. Or at least I thought I did! Glad you found the problem and letting us know for future reference. You did a fantastic job of finding and repairing your problem. :-)

Some batteries seem to "leak" acid out and this acid likes to eat metal and wiring. Ain't pretty either and I have seen it too many times! :-( I am real picky about which batteries I install, but I have been this way since the batteries were installed under the seats of most of the aircooled VWs!!!

later, dave (>> >>

Very, very good. You are excellent! I think my Jetta has a similar problem. I ran a quick test just before the winter and I was stumped. So, I hope you guys don't forget me this summer if my car starts to overheat and give me trouble!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

i've 'milked' a car home with running the heater and fan full bore. I didn't like the heat but the car liked the cooling gained.