Herman K

The (2) cooling fans come on (engine is cold) when the ignition is turned on. I assume that the radiator switch is stuck and stays closed to ground. I removed relay XVIII and it’s the same story with the relay removed. Anybody has been there before?

94 GTS 5 speed

Podguy

A failed radiator switch is supposed to fail with the fans on. After that you have to look at wiring.

Good Luck

Dan the Pod Guy

SwayBar

If the temp sensor located on top of the intake by the flappy fails, it will cause your fans to run all the time, so I would check it out.

Gary Knox

I had the same experience with the '94 GTS I bought a year ago. Fans continued to run all the time on the first day out of Houston!! I pulled the wire off the switch on the top of the intake manifold when I stopped the first night and they stopped. Changed that switch when I got home and they've functioned perfectly ever since.

Gary Knox
West Chester, PA

WallyP

If the switch on the top of the intake fails, the fans will run whether the ignition is on or off.

If the fans run only when the ignition is on, WITH THE A/C OFF (they should run with the A/C operating), it is possible that the fan swith on the lower forward left corner of the radiator is faulty, or that the A/C pressure fan switch on the receiver/dryer is faulty, or that the torque converter temp fan switch is faulty (autos only)...

borland

WSM provides a detailed troubleshooting procedure on the various sensors.

Nichols 928 Tips web site details repairing the controller.

Herman K

If the fans run only when the ignition is on, WITH THE A/C OFF (they should run with the A/C operating), it is possible that the fan swith on the lower forward left corner of the radiator is faulty.

Thanks Wally - In my case the A/C is off and they run when I turn on the ignition key. I'll check out the various procedures you guys have posted and let you know what I'll find.

Thank everybody for your help.

94 GTS 5 spd

fraggle

My vote is the TEMPII switch on top of the intake near the flappy. I had the same issue. Of course I replaced the temp switch on the bottom of the rad, first. Oops.

dr bob

Thoughts--

The ATF temp switch causes the fans to run regardless of ignition switch position. It's wired in parallel with the temp switch on top of the intake. That switch on the intake is NOT the temp-II sensor, by the way. Temp-II sensor is on the water bridge in front of the intake, the one closest to the center IIRC.

The failure mode of the SENSOR on the radiator is for fans-run when the key is on. This is not a switch, in spite of the device name in the WSM wiring diagram. It is a reverse-coefficient thermistor, with higher resistance indicating a higher temp in the radiiator. An open circuit = high resistance = high temperature as far as the controller is concerned. I'd check the connections on that sensor, but might do it from the connector to the controller under the cover in the passenger compartment next to the passenger seat. Using a decent DMM, you'll be able to tell quickly if the circuit is open using just the resistance scale. The temp curve is pretty responsive, so you can watch the engine cool off as you test.


There are some possible failure modes for the amplifier unit on the front apron that might give you the symptoms you describe. We can get to those if the common-simple stuff doesn't take care of the problem for you.

Alan

Herman,
Dr Bob has some good pointers here - as usual! try those

As I mentioned in my PM - I think it could be the fan drive final stages - finned black thing on top of front clip in front of radiator passenger side... If all the switches/sensors checlk out OK and you've swapped the control unit (pass sill) there isn't much left. Any chance of a swap out with someone for this ?

There are no CE panel relays that affect this directly - certainly not XVIII (which anyway should not exist on your car...? reverse light relay bridge for MT... ?)

I'll take another look... tomorrow

Alan

dr bob

One more clue from Wally's post-- the fans rspond to AC system pressure, measured using a pressure transducer on the plumbing next to the receiver/dryer in front of the radiator on the right (pass side on US cars) side. The transducer is a round can, ~1.25" diameter with a couple wire terminals connected and secured with black thumbscrew nuts. Lift one or both of the wires off that sensor, no tools required, and see if the condition changes. If so, that transducer may be bad. Although I've never actually heard of one failing, it's a simple test and an easy fix. You can change that transducer without losing refrigerant, since there's a Schraeder valve in the port that it screws on to.

SteveG

Bob/anybody have pics of the fan controller under the passenger sill cover? As you may remember I have electrical issues with the CD player on the GTS (still haven't resolved that). I was in that cover months ago and found a rather large component with German manufacturer so I assumed that is not aftermarket, but do not know what it does. IIRC there may have been other stuff in there. It was a rather tight fit. Side note: I did find a blown 3 amp mini fuse on the Sirius unit mounted next to the CD changer. It worked the first time I turned it on, then not since. It must have sent Sirius a message and noone paying the monthly charges since ??, It now only lights up, no reception. I will take pics, but that won't be for a couple weeks.

Alan

As Dr Bob says there is the AC system pressure switch - on a GTS its a triple switch - looks the same, same place.

One switch drops the compressor out if the system pressure is too low (<2bar) or too high (>32bar), the other switch closes at the nominal pressure point for the system (18 Bar). When the pressure is above optimum I think both fans contantly run... so you might want to check that switch operation:

The two Black wires to pins 1 & 4 should normally be closed circuit (except when the system pressure is too high or low)

The Brown/Black & Brown/Grey wires (pins 3 & 2) should be open circuit when the AC has been off for a while and system pressure equalizes somewhat...

Alan

Herman K

Ok, I checked my connection (per DR Bob)to the A/C transducer it's a snap-on 4 wire connection (Alan can confirm this as he has a 94 also) and the symptoms are the still with the connector removed from the transducer and the ignition on the fans run, turning the ignition off the fans are off.

I’ll now have remove the wires from the intake switch (above the flappy), radiator and A/C transducer and the fans still come on when the ignition is turned on.

With the ignition on and the above condition all switch wires disconnected the fans will turn of if I pull the number 1 plug on the controller by the passenger seat.

I also disconnected the wires/connector on the coolant bridge sensor and the symptoms are still the same. Ok I’ll keep at it; I appreciate all the help I got so far.

Thanks.

94 GTS 5 spd

Alan

Herman - I meant for you to test the switch... however - try this - with the plug disconnected - link the plug pins 1 & 4 from the 2 black wires - any difference?

Alan