Radiator fans on all the time

jeclarke · #1 (**permalink**) 04-23-2018, 01:19 PM

I drove car 3174 to a garage around noon today to complete the inspection process. 2 hours later, back home, i wash the car for the first time. After drying the car i go to get in and before I’m in the seat both fans come on. They stayed on until I could disconnect the battery. Water temp is almost back to ambient.

Any ideas? Wondering if something electrical got wet and shorted in the fan circuit.

Thanks,
John

Mark IV · #2 (**permalink**) 04-23-2018, 01:41 PM

Quote:

Originally Posted by jeclarke

I drove car 3174 to a garage around noon today to complete the inspection process. 2 hours later, back home, i wash the car for the first time. After drying the car i go to get in and before I’m in the seat both fans come on. They stayed on until I could disconnect the battery. Water temp is almost back to ambient.

Any ideas? Wondering if something electrical got wet and shorted in the fan circuit.

Thanks,
John

Do you have the fan override switch on dash "on"? That will run them whenever the ignition is on. Easy to do.

Otherwise perhaps the temp switch has failed. You can test it by pulling the leads off it and checking continuity, if it has continuity when the car is cool it has failed. Let me know if you need a NAPA part number for a replacement.

jeclarke · #3 (**permalink**) 04-23-2018, 03:18 PM

The key was not even in the ignition and the fans came on.

Looks like getting to the temp switch to check it is difficult. Can i get to it by removing the fans and shroud on the engine side?

jeclarke · #4 (**permalink**) 04-23-2018, 03:20 PM

Please send the NAPA replacement number.

twobjshelbys · #5 (**permalink**) 04-23-2018, 04:17 PM

Fans aren't controlled directly but through a relay. Look at the relays.

snapier · #6 (**permalink**) 04-23-2018, 05:37 PM

I have a Superformance SPO1400 and if the engine is hot enough the fans will run until the engine cools, even if the ignition switch is turned off.

jhv48 · #7 (**permalink**) 04-23-2018, 06:46 PM

Before you start tearing into everything, let the car sit overnight and dry out. Then reconnect the battery. My guess is that some water got to the electrics and is causing the short. You can even leave it in the sun for a while to help the dry out process. The switch on the dash is probably the culprit.

By the way, you do know there is a toggle switch on the dash that turns the fans on/off regardless if the ignition switch is on. I’ve hit it accidentally many times while cleaning with a towel.

Blas · #8 (**permalink**) 04-24-2018, 07:03 AM

The switch on the dash is a second manual ground source to the fan relays. The primary ground source for the fan relays is the temp switch on the lower left side of the radiator. When that temp switch reaches a preset temp, it closes and sends a ground signal to the fan relays trigger circuit and the fans turn on. Same as you would do with the manual fan switch except the manual switch will run the fans till the battery is dead the temp switch won’t. The manual fan switch works regardless of temperature or ignition switch position.
You can replace the temp switch without removing the shroud but you may need to trim a little fiberglass to allow access with a deep well socket. I would first take it out of the circuit when the fans are running incorrectly to see if that is the source of the ground signal. Then do the same for the manual switch on the dash.if removing one or both does not stop the fans I would replace both the fan relays being careful to get the correct style relays. Take a photo of the wiring, remove a relay and take it to the parts store. I hand heard of fans coming on after wash a car before, I am assuming the fuse panel was not drenched in the process. My money is on the relays unless water played a part.

jeclarke · #9 (**permalink**) 04-25-2018, 07:16 AM

Thanks for all the advice. After sitting overnight i reattached the battery cable and the fans did NOT go on. So in summary i washed the car, 2 hours later the fans went on by themselves. 4 hours after that the fans still turned on when i attached the battery cables. Car sits overnight and then things are back to normal.

I now know what the switch looks like and where it is. No way washing the car shorted this out. Did not get the dash or interior wet when washing.

So it was a water problem that I don’t understand or a poor quality electrical part that has an intermittant problem.

Blas - you suggest changing both relays. Would both have failed at the same time? Both fans were on during my issue.

STEVE-O · #10 (**permalink**) 04-25-2018, 07:58 AM

John,
It sounds like this is a very new car. You may find it very helpful to have one of the wiring schematics sold by Blas. They are very detailed and useful when trying to troubleshoot issues.

Also may want to join the superformance owners group. LOTS of info there as well as help with issues.

Superformance Cobra Owners Forum

Detroit Bill · #11 (**permalink**) 04-25-2018, 08:08 AM

Quote:

Originally Posted by jeclarke

I drove car 3174 to a garage around noon today to complete the inspection process. 2 hours later, back home, i wash the car for the first time. After drying the car i go to get in and before I’m in the seat both fans come on. They stayed on until I could disconnect the battery. Water temp is almost back to ambient.

Any ideas? Wondering if something electrical got wet and shorted in the fan circuit.

Thanks,
John

It’s likely a sensor on the radiator. Not expensive but hard to get at.
I am sure Rick will chime in with a part number.

jeclarke · #12 (**permalink**) 04-25-2018, 02:44 PM

I appreciate the additional info. I am already pretty well connected. I have a schematic from Blas, am a member of SCOF, and am friends with Mark.

Blas · #13 (**permalink**) 04-25-2018, 07:04 PM

I suggested changing out the relays first because they are inexpensive and extremely easy to replace. The radiator temp sensor replacement will require jacking the car, draining the radiator and refilling and removing the trapped air, possibly a little trimming of fiberglass and from my experience - 2 deep well sockets if you do not already have them. The relays have been problematic depending where they are sourced and the life they have led.... just my a suggestion - I try to do the easy fix first usually. I could be wrong, but I could be right. Question is: "Are you feeling lucky?"
BTW: I personally run a slightly reduced temperature fan switch. Some people disagree, but we are talking radiator temperature and not block temperature.
And thank you Steve-O for the kind words.
Part number for the std. temp sensors is on your Wiring Diagram like so many other part numbers.
Blas

Detroit Bill · #14 (**permalink**) 04-26-2018, 04:53 AM

I had a similar intermittent issue. I still believe in the end you may end up changing that sensor.

SN8K IS Wife · #15 (**permalink**) 05-16-2018, 09:24 PM

We had the same problem it was the relay.

jeclarke · #16 (**permalink**) 05-17-2018, 05:56 AM

It turns out my problem is the dash fan switch. Both fabs turned on by themselves again last week and stayed on. I unplugged the radiator switch and the fans continued to run.

I found the dash switch to be the problem. Sometimes it works as it should. Sometimes the fans only turn off when the switch is held in the mid- position. Sometimes the fans only turn off when one applies pressure to the side of the switch.

Blas · #17 (**permalink**) 05-17-2018, 07:16 AM

Excellent detective work. This is the first I have heard about that simple switch being the problem. I would have thought that you had cycled it a few times when the fans were stuck on and that they would have turned off at least once. I will add this to the lessons learned database I keep.
Blas