Coolant fan not working (Full Version)

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Coolant fan not working

  

cozmor -> Coolant fan not working (8/18/2007 7:42:09 PM)

1995 90Q - V6
Hi to all,
Maybe someone can point me in the right direction. My coolant fan on the radiator is not coming on at all and is causing overheating. Could this be as simple as a relay? if so which one? I have checked the fuses and all are fine. any help would be appreciated.

Thanks
cozmor

  
hubturn -> RE: Coolant fan not working (8/19/2007 9:36:38 AM)

Turn your airconditioning on.  If the fans run, then the fans are OK.  Pull the connector off the coolant switch on the radiator and jump the connectors. Should be three contact points. One side is high speed the other low speed. Put a jumper wire from the middle to each side.  Fans should run.  If they do, the switch is faulty.  If they don't then you may have a faulty relay.  That's a start at the troubleshooting. Assumes a single failure and not a switch and a relay.

cozmor -> RE: Coolant fan not working (8/19/2007 12:23:56 PM)

Thanks hubturn,
I did the check on the coolant switch and got fan on one side and no fan on other side. Maybe a faulty switch and a relay? What do you think?

cozmor

hubturn -> RE: Coolant fan not working (8/19/2007 1:37:38 PM)

I have a '95 Cabriolet, which may differ some from you '95Q, but I figured they would be close in design.  Did both fans come on with the Air Cond so we know both fans operate? The AC turns on both fans regardless of coolant temperature. First problem in diagnosis is that not all the relays will be where they are suppossed to be.  Audi has a note saying they can be in different locations from where the manual says they should be. The second speed fan relay is powered through a 60amp fuse that in my car is under the dash in the aux relay panel.  It will (probably) have a big red wire running to it. You may have to remove the lower left portion of the dash to get at it. 4 screws, no problem.  There may be a sticker on the inside of that dash panel listing the relays in the aux relay panel. You are looking for the second speed, and third speed fan relays.  Check out the fuse first, then put a jumper back in the radiator switch from the center to both sides and  then tap on those relays to see if one is stuck.  Check to see if the other fan came on.  Alternatively, replace the relays with the same numbered relay from some other system and see if it works.  You might check out the resistor plate near the left front.  It is a plate that has three contact points on it with wires running to it.  That may need to be cleaned to ensure good electrical contacts for the fans. The switch in the radiator is about $45, and needs a gasket too. I haven't done it yet, but my Audi dealer says remove the switch and quickly replace it and you will only lose about a quart of fluid.  This is suppossedly better than draining and refilling and bleeding the system. Right now I'd say a relay or that fuse is a problem since the fan didn't come on during the initial test of the switch.  I'll be gone for 3 days. Hope you find the problem.

cozmor -> RE: Coolant fan not working (8/19/2007 4:27:16 PM)

Thanks for the info! I think it is probably the switch. I found all of the relays for the three speeds and jumped them and the fans ran on each one. I mis communated before. On the coolant switch,  I got both fans to come on when I jumped the center connector to the left pin, I got no fans on the center to the right pin. I will do again with your suggestions. I priced the switch and the cheapest I could find it locally was 92.00. Have a good trip and thanks again.
cozmor

hubturn -> RE: Coolant fan not working (8/21/2007 6:48:57 PM)

At my Audi dealer the switch was $23.56, part number 191-959-481 C and gasket was $1.32, part number N-043-808-3.  Unless there is a big difference between a '95 Cab 2.8L and a '95 Quatro V6, your are getting a bad deal. I didn't remember correctly on the price.  My Audi parts guy says the Audi mechanics get a bucket ready and the switch ready and remove the switch and quickly replace it with the new one and it's gasket.  They say they only lose about a quart of fluid, and it's easier than draining the whole system.  I can't attest to it as I haven't done mine yet but that's what I'll try first.

cozmor -> RE: Coolant fan not working (8/21/2007 7:30:00 PM)

I ended up buying the switch off the net for 17.37. I installed and only lost a minute amount of coolant. was a easy ordeal. I filled her back up and started her up for a test drive. My excitement faded as the temp gauge kept rising. Still overheating!! What is next? I replaced a couple of relays also while I was in a fixing mood. Don't know if they were bad or not. Fans never came on. back to square one. Any ideas?

cozmor

hubturn -> RE: Coolant fan not working (8/22/2007 6:42:13 AM)

From the initial post I figured you were sure you had a fan problem.  Now I'd suspect thermostat.  My fans don't come on until I've been idling and the temp gauge starts rising. For you to overheat so quickly makes me suspect you don't have any flow. Switch F76 in the coolant pipe (metal pipe near back of engine) sends a signal to the instrument gauge and this is independent of the switch sending info to the fan system (the one you replaced).  Switch F76 could be bad and giving you a bad indication, if you are only using the gauge to determine that you are overheating.  Is the radiator and lower hose hot? The switch you replaced won't activate unless you get hot coolant to it. Stage one fan activates at 198F-207F. Water boils at 212F so you would know if hot coolant is circulating because those hoses would be HOT. Check that out.  Thermostat replacement starts a new series of  'while you're there you might as well replace....' issues.  Go to www.12v.org and read up on the procedures. I know this is infuriating.

cozmor -> RE: Coolant fan not working (8/27/2007 6:21:08 AM)

Hey Hub,
Thanks for all your help. I replaced the thermostat and overheating problem went away. I had a coolant leak that I could not isolate. Took to a shop to have it pressure tested and found the leak was coming from the water pump. I had noticed that it was making some noise and was concerned. The shop gave me a price of $906.00 to do the waterpump, timing belt, thermostat, tension rollers. I thought that was a pretty good price compared to what I have read on here. I am waiting to get it back this afternoon or tomorrow. Thanks for your help.

cozmor

hubturn -> RE: Coolant fan not working (8/27/2007 1:27:15 PM)

Glad to be of help.  From your other posts, it seems we are both on the same road of repairs, with me a little bit ahead of you.  I've already done the water pump, etc, the ignition switch, and trouble shot the fans. Next time it's your turn to be the guinea pig and give me advice. I hope your shop does a nice job.

Hubturn

  

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