Cooling Fan Switch, a short circuit, or what????

the timmer · the timmer's Garage

Just a few weeks ago, my 1988 N/A cooling fan(s) started to run as soon as I turned the ignition. One dead battery later (suspected cause was leaving a light on in the car for 4 days but at this point who knows) I just now put the car into the shop (the same one that worked on my car last August where they replaced the cooling switch, among other things) and they first determined that the fan relay was bad and recommended a replacement for $200. After looking online, I found out that I could get the relay and install it myself for a mere $129 or less! I called back the shop, told them that I'd like to pick up the car and take care of it myself (they were doing other minor things to the car, as always) and they agreed.

I arrive and they reversed their story and said that BOTH the relay and the switch are fine so they suspect that the constant running of the fan is caused by a short in the circuit. Let me include that the seat belt warning indicator light remains on ALL THE TIME and they think it's possibly related to the cooling fan short.

I pay the man, take the car, and drive off a few blocks to park and remove the relay. With the relay off, the fan stops, leading me to believe that the relay is fine but possibly the switch (installed back in August) is bad. Or is it a short circuit somewhere else in the car that the mechanic suspects? Anywhoo, he wants to charge at least 3 hours to look more into it and we got a Thursday appointment for me to bring the car back in.

So, in that time, what actions can I do on my own to confirm that it's either a bad switch or really a short circuit? I'm not to mechanically inclined but from reading this board, checking the fan switch may require an hour or two of removing hoses and other things which don't seem too complex. Please advise.

thks,
-timmer

Gene Alvarez · 04-12-2003, 05:47 PM

Looking at the wiring diagram, the fan circuit is pretty simple, not much chance of some mysterious "short". Either the cooling switch or the AC will activate the relay, but if the switch is not on, only one fan will run for the AC. If the AC is off and the switch turns on both fans will run.

Try this: unplug the switch. If the relay is good the fans should not run. Now turn on the AC with the car running. One fan should come on, further proof that the relay is good and the switch bad.

the timmer · the timmer's Garage

Ok, so I went into the car today. Here is what I found.

1. When both the relay and the electrical connector to the switch* are both on, the fans blow when the key is in the ignition.
2. When the relay is removed, the fans stop
3. When the relay is back on and the electrical connector to the switch off, the fans continue to blow.

So, what can the above tell me what's wrong? Please advise as my shop thinks it's some short circuit somewhere that's causing the fans to run continuously when the key is in the ignition.

* the electrical connector that I think was what I supposed to disconnect was just under the hose that connects to the upper driver side part of the radiator. I hope that was it. From reading clarks garage and posts around here, I think it was the correct connector.

Gene Alvarez · 04-14-2003, 10:34 AM

I think you disconnected the right connector for the thermo switch. Did your shop actually try replacing the relay (it's not cheap)? With a couple of pieces of wire and a light or ohmmeter someone could determine if the relay is OK. Maybe, if the relay cover comes off (I don't know) you could see if the contacts are stuck on and gently pry them apart. If the latter is the case, I would buy a new relay even though the old one might start working again for a while. Stuck relay sound more likely than a stray ground.
Gene

the timmer · the timmer's Garage

thks for the reply. I read somewhere in the archives that to test the relay, remove the relay and if the fans stop then the relay is good. IF the fans continue, the relay is bad. On my car the relay was removed and the fans stopped, leading to a good relay.

However, the shop initially said that the relay is bad but reversed their statement from between the time I said I'll pick up the car and actually picking up the car. I suspect that they wanted to charge me $200 for a $100 part and when I said that I can find it on my own, they wanted to charge at least 3 hours ($81/hr) to correct this new mysterious short circuit. I don't know anything about electronics but many sources here say that initial testing of the relay says that it's good.