The dual fans in my car will not turn off after they come on. They are factory dual fans and I am using a Hypertech Fan switch (on at 200 off at 185), and this dual fan wiring harness.

http://www.ebay.com/itm/DUAL-ELECTRI...a3d106&vxp=mtr

I thought that maybe the fan switch from the wiring kit was faulty so I put in the hypertech one, but they still won't shut off after they come on. What should I look for?

I suspect your engine is not getting cool enough for the temp switches "off" temp of 185 to drop out the ground signal to the Spal relay. Have you tried a higher temp range switch? The ones I stock are 215/204 on/off. With my harness kits that seems to be optimum. This keeps the engine running right @ 200F.

I just received my car back from the electrical shop over the weekend and one of the things they had to replace was the computer, due to the dual fans not shutting off. A friend of mine once had that same problem as well.

As mentioned, the shop did the testing/replacement, but I'm sure if you search the related computer forums, you'll find test methods there. As a reference, the refurbished computer put in cost me $150.00.

1989 TransAM GTA 5.7L

I am having the EXACT SAME problem. Fans will come on at temp, but never switch off (unless I kill the ignition). Even when I turn the key back to the 'ON' position, without actually starting the engine, the fans BOTH kick on a full speed. VERY STRANGE.

I have replaced the Coolant Temp Sensor (under throttle body), the Hypertech Fan Swich (200 Deg. ON, 185 OFF) on the passenger side engine block, and also tested the cofirmed that both relays are OK.

For good measure, since the water was mostly out of the engine, I changed to a Stant SuperStat 195 Degree.

The LAST thing to change would be the ECM.

DID REPLACING IT SOLVE YOUR PROBLEM??

Thanks for the help.

How are you EVER going to get the coolant back down to 185° with your Hypertech fan switch if you have a 195° thermostat in there?

Even with a 180° thermostat in there, it's very unlikely (unless it's super cold outside) that you'll get the coolant down to 184° in order to shut off the fan when you have a 200/185° fan switch.

Ok - One more critical clue:

When car is cold, and I switch ON the A/C - None of the fans come on.

I swapped ECM yesterday with a CARDONE one - and also swapped PROM. Same symptoms as before. Both fans come on at around 160 and never switch off. EVER.

Any other thoughts guys? I am ready to drive this car into the river.

THANKS in advance.

If you have a 195 stat, the temp doesn't get cool enough for them to turn off at 185.

Never tried the ECM. My car has a 180 degree thermostat in it.

Thanks for the replies:

But to keep it simple - here are the symptoms:

(1) When car is cold, and I turn on AC - NO FANS TURN ON

(2) When car gets to about 160 degrees (before fan switch needs to activate) - BOTH FANS TURN ON.

(3) These fans WILL NOT turn off or cycle as they should (and used to until last week).

(4) If I swich OFF the car, but then turn the key back to ON position without starting it - BOTH FANS ARE STILL STUCK ON.

Replaced: ECM, Fan Switch on block, Coolant Temp. Sensor under Thottle Body.
What else could be telling the ECM to turn on BOTH FANS and keep them pinned on?

Thanks for the help. I don't want to have to resort to an aftermarket fan control system If I don't have to. Unlinke most 3rd Gens, and am NOT OVERHEATING - Quite the opposite the car won't get up to temperature.

HiTech- I had the exact same issues a few years back. Do you have headers? My cause was do to the wiringhat goes along the side of the block being burnt on the headers (passenger side). Prior to diagnosing the problem, I had replaced the fan motor (both), fan relay, fan switch, coolant temp sensor and swapped the ecm and still no fix. I was able to get a copy of the wiring schematic from the local dealership and found the culprit.

Hope this helps.

Keep us posted.

I do NOT have have headers - stock 5.7 TPI rusty exhaust manifold.

Which wire was melted on your car? The Fan Switch wire going into the block? Or others?

I could easily run a fresh wire from from the new fan switch to the ECM - but I would then have to cut that wire at the ECM harness and splice it to test this theory.

Even if this is the case - WHY ISN'T the AUX FAN SWITCHING ON when I put on my A/C ON when the car is cold? What tells the ECM to to switch on the Aux Fan when A/C is switched on?

Then, regardless - Both fans come on at or before 160 degrees and never turn off.

VERY Weird.

Thanks for the help!!

Sorry, I should have been more specific. It was the wire for the fan switch, however I would check the all wiring to make sure that there are not pinched, etc...

Can anyone help me

I have an 89 formule 5.7
I turn the key in the on position and the secondary fan turns on before I even turn the engine over. When I turn the engine on they both are on. Car is cold and both fans are on? I've checked all the relays and coolant temperature sensor and replaced the thermostat. Any suggestions?
Thanks Laura

In 85 the carbed IROC had a mechanical fan, the TPI a single electric. So which did your car have from the factory and how was it converted to dual electrics?

JamesC

how bad is it to just let fans run constant, my 91 rs fans trn on when key is on position but not turnin motor over they are on. is that a big problem in the long run?

Do you have good voltage going tho the relays? Bad alternator? Jump it with a charger or another battery......I bet they'll work then.

I'd call the OP's thread officially hijacked.

JamesC

If both fans were on and you turn the car off while the engine is still warm. Turning the key back to ON (with engine off) will turn the fans back on. This is normal. Drag racers do this in the pits all the time.


What do you have the dash HVAC settings on when this happens? Heat? A/C? MAX A/C? OFF? DEF?

It sounds to me like you might have gotten the Hypertech 176/166 fan switch by mistake. This would turn both fans on very early. They'd never go off unless you get the car to 165° at less than 40 mph (doubtful even with a 160° thermostat. And impossible with a 180° or 195° thermostat)

Since this is December and I assume it's cold where you live, we can reason a few things.

1) The passenger fan turns on with the A/C when it's at 233 psi or higher on the high side A/C pressure. It shuts off at 190 psi. In spring and fall it's easy enough to cycle back and forth between 190-233 psi when the A/C is on. During summer, you're generally always above 233 psi (passenger fan stays on). In winter time you're not moving enough heat (high side pressure) through the condenser to warrant turning on the passenger fan.

2) You won't read about this anywhere else. But again since it's December, and a lot of us are running the Defrost (which uses A/C), we might only have the compressor on for 5-10 seconds. Depends on ambient temp. Depends on moving or stopped at a light. Depends on if you're low on refrigerant or not. All effect the run time of the compressor. What I've noticed is that short compressor run times with the defrost setting selected won't turn on the driver's side fan, even though anytime the A/C is on, the driver's side fan should be on. My theory on this? I know once the driver's side fan turns on, it will stay on for 15 seconds regardless. But I don't know if there is a 15 second off delay as well. If there is, then this would explain why the Defrost (A/C) can be on and cycling the compressor even though BOTH fans are off.


High side pressure in the A/C system. You won't have enough of it this time of year to turn on the passenger fan.

Do the fans turn on during a cold start with the key turned to ON (Engine off)? Or only if you turn the key to ON after shutting the engine off while it's warm?

Both fans will turn on for about 20, maybe 30 seconds after starting the car up. They should go off after that (if you have the dash set for OFF, VENT, or HEAT......Having it in any other setting will generally mean that one or both fans will be on.)

I wouldn't worry about it too much. Being in Dallas, your fans are probably on 99% of the time from April-October like mine are in Houston.

Fan motors can wear out. Not that expensive. I see it more as a waste of energy, voltage, and power to run the fans needlessly.

https://www.thirdgen.org/forums/cool...ans-arent.html

Check out my signature for schematics and descriptions of how/when our fans run. Click the link above for a longer explanation on why and when the fans are on/off.

My car came originally with a single electric fan. I bought a used dual fan set up and purchased a dual fan wiring harness from SPAL I believe.

hi, you seem to be THE person to talk to,,,, i have an 86 trans am , i dropped a built 355 tpi in there, with a aluminum 3 row rad, the ecm and wiring is from a 87 iroc, i deleted the a/c, even the heater, only gonna drive in summer when weather is good. now my question,, i dont have dual fans in the car i have the stock 86 single fan, since i dont have a/c , and i deleted half the harness to have only one relay to my fan,,,, now what should i use to trigger that single fan? i have, 1. the stock temp switch on pass head,2.a temp switch on my new rad 3. the ecm that takes the info from that temp switch on the intake below throttle body, can i use the gre/wh wire from the ecm and both switches on the same relay?? should i rely only on ecm? only on 1 switch? 2 switches? if i use the ecm at all,,,, since i have an 87 wiring, do i ground, or open the blue wire from the a/c? cause i dont have a/c ,,,the car i took the ecm and wire from used to have a/c. if i dont use the ecm,, can i just leave it like that or is there something i should change not to mess up anything,,,,,, i just dont wanna try a bunch of things, want to wire the car properly once,, and hide harness with loom once and for all,thanks.sorry for the looooong question

**UPDATE**

I have finally decided that the wiring IS faulty between the sensors and ECU.

I have opted to install the DAKOTA DIGITAL fan control unit with TWO Relays for full dual fan mode.

Here is my setup:

Dakota Digital PAC-2750
Dakota Digital SEN-04-2 (3/8" NPT sending unit screws right in place of stock fan switch on engine block. This unit is PERFECTLY CALIBRATED for the Dakota Digital control unit. It is an actual temperature sensor, not just a "switch")
Dakota Digital RLY-3 - additional 70AMP Relay.

HOT TIP: The control unit MUST be installed inside the vehicle - and has 7 wires that feed into it. I went to Home Depot and purchased 25 Feet of Sprinkler wire (Irrigation wire) that had a nice thick insulation and 7 conductors inside. All I had to do was drill thru the firewall on the passenger side and run ONE wire thru to the control unit. I ran the wire where the stock fan relays once where (I cut those suckers OUT!!)

It works PERFECT! I can even control at exactly what temp the fan comes on at, how many fans switch on, and can see EXACTLY what temp the water is in the engine with the little digital readout.

I tried the HAYDEN crap-ola first, and returned it to PepBoys.

SUMMIT RACING had all of the Dakota Digital products and it was worht the few extra bucks to have this system fully under my control.

If you have any questions - let me know.