Fan Runs Continuosly - When Ignition Is On

[turbo79]

Driving my '92 yesterday, I noticed after a few miles that the cooling fan was not shutting off at all. It now comes on when the engine is first started, cold or warmed up. Anyone have a suggestion what might cause this? Could it be a failure of the ACT sensor? Or should I check the CCRM? Or both??

The only thing that was done to the car between the time it was driven last and yesterday (about a week) is that I spent some time 'burping' the cooling system to purge air from the upper part of the cooling system (squeezing the upper radiator hose while the car warmed up, with the radiator cap off to watch as air was removed).

The 'burping' did work, in that the heater now works as it should, putting out proper warmth that it didn't before. Could this 'burping' have somehow caused the ACT sensor to fail and cause it to default to a temp. reading hot enough to cause the fan to run, even when the car is cold right after start up?

 

[sperold]

If you tap the top of the CCRM, does the fan go off?
Clean up your grounds that are associated with the Powertrain Control Module (PCM).
It could be your PCM, but the grounds are the place to start.
I don't think it is the ACT sensor.

 

[rubydist]

what are the codes?

 

[turbo79]

If you tap the top of the CCRM, does the fan go off?
Clean up your grounds that are associated with the Powertrain Control Module (PCM).
It could be your PCM, but the grounds are the place to start.
I don't think it is the ACT sensor.

I should have typed 'ECT sensor,' not 'A.' I'll check the grounds for certain. And I'll try the 'tap the CCRM' trick.
Thanks!
Tom F.

 

[turbo79]

what are the codes?

I'll check in a day or so, and post same.

 

[sperold]

The battery negative cable at the battery has a small wire coming off it that attaches to the inner fender (very near the battery). At that attachment point is another wire that is heading for the strut tower. There is a connector in that wire (still near the battery) that you can take apart and clean. The wire goes to 2 splice points and branches run to the EEC (PCM) (pins 60 and 40), the IRCM (CCRM) (pin 16) and your MAF (mass airflow sensor) directly. All wires are black with a light green stripe after the connector. On the battery side of the connector, the wires are black.
Clean up that first inner fender connection point and the first connector, to start with.

 

[rubydist]

it is possible that the ect sensor is bad and causing the pcm to command fans on at all times, but that is much less likely than the other options - ccrm sticking or bad ground somewhere. that is why I asked for codes - it should help you narrow it down.

 

[turbo79]

The battery negative cable at the battery has a small wire coming off it that attaches to the inner fender (very near the battery). At that attachment point is another wire that is heading for the strut tower. There is a connector in that wire (still near the battery) that you can take apart and clean. The wire goes to 2 splice points and branches run to the EEC (PCM) (pins 60 and 40), the IRCM (CCRM) (pin 16) and your MAF (mass airflow sensor) directly. All wires are black with a light green stripe after the connector. On the battery side of the connector, the wires are black.
Clean up that first inner fender connection point and the first connector, to start with.

Sperold, I really appreciate this detail. I will check and clean those points you list.

I am a believer in a little overkill in grounding: I have a ground strap going from the negative battery connection at the post to the intake manifold near the DIS (in additional to the OEM grounding on the back of the manifold), and a short ground to the chassis - the metal (header?) panel that the CCRM mounts on - from the ground pin in the CCRM.

Thanks again!

 

[itwonder]

Could it be as simple as the automatic climate control has the A/C turned on? If the A/C compressor is engaged, the fan will run. The PCM will shut it off when the vehicle reaches 40 mph.

 

[sperold]

Just something that happened to me that may help you.
When I first turned on the key, my fans would run for a few seconds and shut off, even if I did not start the car. It was annoying but never an issue, because I knew the fans were off when the car was warming up.

When I was troubleshooting my air bag light issue, I ran a dedicated ground wire to each of the 3 front crash sensors. I noticed the fans did not come on when I did this, but ignored the findings as I am always in a hurry.
Today I installed an end on my ground wire (which I had taped up and hidden) and took one of my 4 screws out of the front crash sensor (on the rad) and put my ground wire on it.

Sure enough, now when I turn the key on, there is no fan activity. Can't explain it, but it worked for me.

I used a 3M ring connects (03858NA) (the yellow ones) which are large enough to go on the battery cable squeeze bolt, behind the nut, and a smaller ring connect (still yellow) for the crash sensor end; and 12 gauge wire in between.

 

[turbo79]

it is possible that the ect sensor is bad and causing the pcm to command fans on at all times, but that is much less likely than the other options - ccrm sticking or bad ground somewhere. that is why I asked for codes - it should help you narrow it down.

Hello Fred.
Yesterday I went ahead and ran the codes (I have a code reader, not a really expensive one, but capable of some text messages describing the codes it finds). Now, I may not have warmed the engine enough (first time) to get a good reading, but here goes:

KOEO
511 (O) No power to PCM pin 1 or bad PCM (processor)
512 (M) Memory power (PCM pin 1) was interrupted - Was battery disconnected ?

Yes it was. I had disconnected battery ground to reset the PCM a day or so before testing, but that did not stop the fans at start up. Then after the 511 and 512 codes I got:
114 (O,R) IAT (Intake Air Temp.) sensor out of range

Kind of mysterious, since it doesn't seem that the intake air measurement would turn the fan on, unlike the ECT (codes below, which I did not get).

116 (O,R) Engine Coolant (ECT) sensor out of range - ECT
117 (O,M) ECT sensor is/was low or grounded - ECT
118 (O,M) ECT sensor is/was high or open - ECT

KOER
225 (R) Knock sensor not tested (ignore if not pinging) - KS

And after clearing the codes with the code reader I got:
111 System checks OK

Now the fan doesn't run until the engine reaches operating temperature, as it should.

Mysterious!
Tom F.

 

[rubydist]

Interesting. It would seem that there may be an intermittent open in the wiring to the pcm, where the power to pin 1 is disrupted from time to time. Or, the connector is dirty so that it does not always see power.

I am curious to see how long everything works before it starts acting up again. Hopefully, a good long time...

 

[turbo79]

Interesting. It would seem that there may be an intermittent open in the wiring to the pcm, where the power to pin 1 is disrupted from time to time. Or, the connector is dirty so that it does not always see power.

I am curious to see how long everything works before it starts acting up again. Hopefully, a good long time...

This is the first time I've had the issue. I hope it's not an interruption in the wiring to 'pin one' - I had a base twEECer installed a few months ago, which of course required that the PCM be disconnected so the twEECer interface could be inserted. Crossing fingers!