Electric fan not running

[Waisthighglass1]

Hey people I have another question. I have a 94 5.7 caprice wagon, the fan is not coming causing it to over heat while idling while the ac is running. Ive checked the voltage and its reading. 03 volts. If anyone has any other options please let me know or maybe how I can jump the fan to rule out a bad motor? Please help me. Thank you

[Fred Kiehl]

Check for voltage at the fan relay. If you have voltage on the high side of the relay, it could be the relay. You can apply voltage and ground to the fan to check it, but it would be easier to check for volatge at the relay first.

[Waisthighglass1]

Hey thanks a lot, but another problem is my car has a mechanical fan and just one electric on the driver side. Would this be another problem?

[Waisthighglass1]

Hey thanks a lot for distinguishing that. I know for a fact that the mechanical is running, so I will start troubleshooting next week on the 2ndary fan. Would it make a difference that it only starts heating up a lot when the AC is running? I still haven't let it run up to the red yet, so I guess technically its not over heating just heating up real slowly while its idling.

[Marky Dissod]

Originally Posted by Marky Dissod, Aug 8th 2012 @ 12:29 AM

1. Replace coolant reservoir cap with a new one (just do it). If your coolant looks like something served at Starbucks, backflush, flush, and backflush your engine, radiator, and heatercore SEPARATELY, and then add new coolant and burp the system of air, BEFORE proceeding to step #2.

2. Disconnect waterpump coolant temp sensor [preferably during COLD start]. Passenger side fan should be on in 5 secs or less, driver side fan on in 10 secs or less [but don't crap your pants over 5 more secs].
3. If one of the fans fails to turn on, check fan relays and fuses, near the windshield wiper motor. (If either or both relays are melty, and they were inside a box with the rest of the fuses/relays, it's time to move them OUTside the box.)
4. Replace any failed fuses.

You can choose to skip the following optional testing procedure …
5. If both relays LOOK OK, switch them.
If the 'dead' fan now 'lives', and the 'live' fan now 'dies', there's the bad relay.
If both fans die, the originally 'dead' circuit just took out the other [good] relay. Either replace that fan motor, upgrade the fan wiring harness, or both.

6. If one fan motor refuses to work with KNOWN GOOD fuses and relays, either replace that fan motor, upgrade the fan wiring harness, or both.

Originally Posted by Marky Dissod, Aug 10th 2012 2:54PM

… amended for 1 mech primary fan, & 1 electrical 2ndary fan.

1. As in previous post.
2. If electrical 2ndary fan is 18 yrs old, just replace it already, then proceed, but note step 4b. Otherwise, note step 4a.
3. Disconnect H2Opump-CTS. If 2ndary electrical fan does NOT come on …
a. replace relay if 'melty', upgraded/relocated wiring harness highly recommended
b. replace fuse if bad
4a. If KNOWN GOOD relay &/or fuse fails AGAIN, replace motor, upgraded/relocated wiring harness highly recommended.
4b. If KNOWN GOOD relay &/or fuse fails AGAIN with KNOWN GOOD motor, upgrade/relocate fan wiring harness absolutely necessary.

Mech [primary] fan should move enough air at idle to prevent - or at least significantly delay - overheating. Test it as well.

One other thing, just in case …
If the Head-Dashboard-Temp-Gauge is MORE THAN 3/4 to the right [of halfway between straightup & red], it's still not overheating yet, but it's time for concern.
Anything less than that, no problems as such, yet.

Originally Posted by Waisthighglass1

Would it make a difference that it only starts heating up a lot when the AC is running?

Yes, it would. Something is wrong.
1. GM's fan-on temp thresholds are ridiculously high [for MpG & emissions reasons], but GM's AC psi thresholds are perfectly reasonable.
2. It's a well known fact that when the AC is on, in an otherwise healthy cooling system, engine temps should remain stable because the primary fan should be running nearly constantly and the 2ndary will come on from time to time to assist … the net effect is that the dash temp needle should never make it past 3/4 to the right with the AC on in an otherwise healthy cooling system.

Besides burping it again and well, you may need a new radiator, or at least a backflush-flush-backflush of your radiator, engine, and heatercore [separately].