Cooling fans on when engine is started.
Thread Starter
3rd Gear
Joined: Dec 2020
Posts: 3
Likes: 0
Cooling fans on when engine is started.
replaced the relays on my 93 because they were burnt up. after doing so now i have both fans working but they come on soon after the engine is started. ecm is commanding the fans to kick on. no sure why and dont know the next step to diagnosing issue. all wires are ok and even made sure the new relays work before wiring them in. in short, fans on when they shouldnt be even tho the ecm is telling them to be on even at 100 degrees
Melting Slicks
Joined: May 2014
Posts: 2,894
Likes: 592
From: New Port Richey FL
Is the a/c on or off, if the a/c is on the fans kick on normally has been my experience.
If not the a/c high pressure switch could still be throwing the fans on
When I first got my car I had to un-Jerry Rig the car from all things the Previous Owner did. Like hard wire the A/C coil to the Cabin Fan so as soon the heat, vent anything that brought enough voltage to turn on A/C coil, turned on cooling fans to. Drove me crazy it kept burning up the coil. Turns out it was the a/c controller under the dash was corroded and dead, which was the original problem that made the need to bypass the a/c control
If not the a/c high pressure switch could still be throwing the fans on
When I first got my car I had to un-Jerry Rig the car from all things the Previous Owner did. Like hard wire the A/C coil to the Cabin Fan so as soon the heat, vent anything that brought enough voltage to turn on A/C coil, turned on cooling fans to. Drove me crazy it kept burning up the coil. Turns out it was the a/c controller under the dash was corroded and dead, which was the original problem that made the need to bypass the a/c control
Last edited by s carter; May 7, 2021 at 05:39 PM.
Drifting
Joined: Jun 2020
Posts: 1,355
Likes: 396
From: Northwest Ohio
Is HVAC completely OFF when this happens... some of the ON settings (even what you think is heat) will trigger AC on...thus fans on. You should have the "feet' setting set if you want HVAC on with no AC running (I believe it runs to adjust the moisture levels even when obviously in "heat" mode otherwise).
But if they are turning on the second you turn the key and HVAC is completely off, then I would start looking at the FSM. Do you have any codes reporting? I'm not sure but if the CCM and ECM cannot talk it might command fans on, or if it is in "code reading" mode (i.e. paperclip jumper in OBD port) it will.
But if they are turning on the second you turn the key and HVAC is completely off, then I would start looking at the FSM. Do you have any codes reporting? I'm not sure but if the CCM and ECM cannot talk it might command fans on, or if it is in "code reading" mode (i.e. paperclip jumper in OBD port) it will.
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
I feel like this is obvious, but just in case it isn't, I'll put it out there. The fans also come on full blast if there's a fault in the ECM. Whenever it goes into "limp" mode, they're on all the time. So if there's a MEMCAL fault or an internal ECM fault it can also cause the fans to be on all the time. But you should also experience other symptoms than just the fans being on with the ignition if that is the case.
