1988 2.5 Fiero Fan not turning on (Page 1/1)
Firezappy NOV 28, 05:57 PM
So I just finally finished getting a junkyard motor pulled and into my old Fiero, it lives! The original engine was warped and not worth the trouble. But now I noticed my front fan won't turn on unless I turn on the a/c. I let it get pretty warm and nothing. I am having trouble, everything I read and the pictures show everything for the 1984-87 and not the 88 2.5. So it appears the fan on the 88 is controlled by the ecm, whats up with that? What do I need to do to figure out whats wrong? If the a/c makes the fan work and the fuses are fine, whats the next step here? Thanks!
theogre NOV 28, 06:22 PM
Yes 87/88 4 cyl ECM runs the Rad fan and turns on ~ 220°F. ECM also runs Cruise Control too wither or not car has the rest of cruise parts.
ignore Temp Gauge that often are not accurate.

See my Cave, Rad Fan

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

[This message has been edited by theogre (edited 11-28-2022).]

dmac35242 NOV 28, 10:08 PM
So if the ecm controls the fan, the coolant temp the ecm sees thru its coolant temp sensor should tell the ecm to trigger the fan, right?

That's standard factory for other GM products of the era.

Check the coolant temp sending unit to the ecm.

See if your coolant sensor is on the top left rear of engine, with a yellow wire and a black wire.

That'll help me know if I'm looking at the right schematic.
theogre NOV 29, 03:51 PM
ECT Sensor is in/on the T-stat tube for all l4.

Sensor works or will have other problems and maybe set code if total dead.
Example: Wiring or sensor "bad" often the ECM reads Way low temp and engine runs way rich if starts at all.

You need a scan tool that tells you Sensor reading and Fan 1 is on or not. Has Fan 2 but not wired and ignore it.

Red devil has scanner works w/ this ECM. https://reddevilriver.com/
(Also tells you cruise on/off etc for that too.)

See my Cave, Scan Tool Help, More on Tools & Sensors Quick Ref
and likely more...
Firezappy MAR 02, 05:53 PM
I looked at the resistance of the ecm temp sensor and it appears to be reading correctly, it is just the gauge appears to be off. The fan kicks on when the gauge says 260, which I hate but so be it. May add a resistor or something and try to get the gauge at least accurate with the fan kick on temp. I guess that is at like 235ish. Now the lock up torque converter is stuck so I undid the wire to get home. As mush as I love these old cars this is getting rough, but I just can't quit...Thanks for the tips. Next up, solenoid, can't be harder then the 2 engine pulls I have done on this car already >.>