I did a search and found a few interesting threads that touch on this topic but do not come to a resolution that helps my situation, so creating new thread.

1992 Firebird 305 TBI - Electric fan does not auto-engage when the car heats up.

The fan engages when I run the AC and engages with a switch I wired into the car that grounds one of the terminals in the relay (this was a temporary fix until I could focus on the main issue).
According to input from previous threads that means the relay and the fan (obviously) work fine.

I recently replaced the Coolant Temp Sensor with an ACDelco ( ).
A while back (when this issue started), I replaced the Temperature Fan Switch with (I think) a Standard Ignition (TS147), which I'm thinking of attempting to find a different brand, but cannot find and ACDelco. But, let's assume the part wasn't DOA and works..

What else could cause this issue? What other item/senor/relay/fuse could have failed here?
Also, what temperature should the fan engage by default (stock)?

Thanks in advance!

 

Soooo...since we're talking TBI, the 1227846 ECM doesn't do any controlling of the Efan and solely relies on the Temperature Fan Switch. My understanding is that switch comes on at a uncomfortable 230dF. Are you boiling over??? The wire going to the TFS can simply be grounded to trigger the relay to operate the fan, Key On Engine Off or Running. If a known good ground works, try grounding it to the body of the TFS. If that doesn't work, maybe too much teflon tape creating no ground??? If everything is working as it should and you don't like that 230dF on temp, perhaps a lower temp switch might be more suited to your liking.

 

So, the fan actually came on this afternoon with no manual intervention. The temp gauge did reach a little over 220. I did replace that coolant temp sensor yesterday, and tested it yesterday but the fan did not come on... so I wasn't aware it was fixed, and I'm still not 100% sure it's working correctly. I'll test again tomorrow as I drive it just about every day.

I am now eyeballing a different fan switch, that has a lower opening temperature, since I'm running a 185 degree thermo I'd like the fan to be somewhere closer to that.

Thanks for the reply, will return when I can confirm it's working 100%.

 

The fan is NOT turning on today unless I engage the AC. I also tested if the fan would engage if I manually grounded the coolant fan switch wire and it does. So, I'm thinking I have a bad switch or ground at the switch. Something you said sparks a thought..

So, the coolant temp switch / sensor needs to be grounded to the block? How? Via touching the body of the block to the hex base of the sensor? I assume this since you stated maybe too much teflon tape preventing a ground..? Should I remove the switch and clean it up (cleaning the area around it) and put back? I'm also wondering if I didn't screw it in enough if when I replaced this switch a few months back...

 

Don't use Teflon tape. Use a high-temperature sealant...

 

Yes. You could simply do a continuity check with a multi-meter between the sensor body and suitable ground preferably the cylinder head or block. Probe light could be used as well. Possibly a bum switch if the ground checks out. On my short 8 mile commute to work and return trip home, as long as there's no stop and go traffic, my electric fan doesn't turn on at all. My switch is set to come on at ~192dF. The forward movement of the vehicle is enough to keep it cool on my commute.