Primary Fan comes on too soon, '88 GTA
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Joined: May 2004
Posts: 105
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From: Memphis
Car: '88 GTA
Engine: 5.7L
Transmission: 700R-4
Primary Fan comes on too soon, '88 GTA
While searching threads for cooling fan issues, I found this semi-recent post:
The driver side fan comes on within a few minutes of the engine being started up cold even in this cold weather. I replaced the CTS (that goes into the intake manifold) a few weeks ago, and the symptoms have stayed the same. Since the ECM controls the primary fan, what should I check next? How can the ECM fan driver be tested?
My gauge has not gotten up to 210ish in a long time, so the quickness of the fan to come on combined with the low gauge reading seems to indicate the fan is clearly coming on too soon.
If both fans are running with the A/C, the fan circuits are working. '87 and older, the A/C only kicked on the single (or primary in dual fan cars).
Since you're is '89, both fans run with A/C
<b>The ECM should turn the primary on at 220°F
The fan switch should turn both (like the A/C) fans on at 238°F in the event the ECM does not kick the primary on.
It is not uncommon for the stock gauge to be off slightly.
It is not uncommon for the ECM to read a different temperature from the gauge due to the sensor/sender locations.
There may be an issue with the ECM fan driver. </b>
Jumping the ALDL A-B terminal (flashing check engine codes) with the KOEO (key on engine off), should make the ECM run the primary fan. If not, the ECM isn't controlling the primary fan.
Unplug the fan switch and ground the wire KOEO, it should make the fans run as well.
It seems a bit odd the ECM and fan switch have both failed.
Since you're is '89, both fans run with A/C
<b>The ECM should turn the primary on at 220°F
The fan switch should turn both (like the A/C) fans on at 238°F in the event the ECM does not kick the primary on.
It is not uncommon for the stock gauge to be off slightly.
It is not uncommon for the ECM to read a different temperature from the gauge due to the sensor/sender locations.
There may be an issue with the ECM fan driver. </b>
Jumping the ALDL A-B terminal (flashing check engine codes) with the KOEO (key on engine off), should make the ECM run the primary fan. If not, the ECM isn't controlling the primary fan.
Unplug the fan switch and ground the wire KOEO, it should make the fans run as well.
It seems a bit odd the ECM and fan switch have both failed.
My gauge has not gotten up to 210ish in a long time, so the quickness of the fan to come on combined with the low gauge reading seems to indicate the fan is clearly coming on too soon.
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Re: Primary Fan comes on too soon, '88 GTA
have you verified that the temp gauge is accurate? it could be that the pri fan is comming at at the right engine temp but the gauge is off.
Thread Starter
Member
Joined: May 2004
Posts: 105
Likes: 0
From: Memphis
Car: '88 GTA
Engine: 5.7L
Transmission: 700R-4
Re: Primary Fan comes on too soon, '88 GTA
I used to drag race with the occasional data logging. If the ECM temp was correct, at an indicated 212F gauge, the ECM displayed 232F. I just disconnected the primary fan and drove it around. It would barely get 1/4 up while moving. It took several minutes idling and some 2K revs to get the gauge to 212F. Though I don't know for certain, I think the gauge is accurate because the fan comes on so soon. It came on within 3-4 minutes and the outside temp was 40F.
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