My 87 Firebird is a 305 carbed car with full gauges and a single cooling fan.

I've been having a problem with the cooling fan not coming on normally. In the A/C (Bi-level, normal and Max) settings it comes on and the engine runs at a decent temp. With it in the heater or defrost mode the fan never comes on and the temps creep up.

Tonight, along with my oil pressure sending unit, I put in a new fan switch in between cylinder 6-8. The one I pulled out had 106C on it and the new one had 110-100. I topped the coolant up and ran it for about 20 minutes to bring it up to temperature. Still no damn fan.

I know the stock gauges aren't accurate, but something isn't right. I don't think it's the relay because it comes on in A/C modes. Or am I wrong on this.

Anyone have any ideas? Thanks

 

buying a new thermostat is iffy let alone those stupid switches, after going thru 3 of them in not even 2 monmths (as a weekend driver) i came to the conclusion that they are crap... And not including that three was one i bought that didn't even work...

Wired my fan to a solenoid with a fusible link to a toggle switch by my dash, never creeps up to 220 at all with a 192 thermostat.

and yes thats highway driving, town driving, even went thorugh town which i took the highway to get there n sat in giant eagle parking lot for 10 mins. nothing

 

I'd prefer not run a switch as I've had enough things ghetto rigged on other cars. I'd rather just not worry about it. I'd probably forget to flip the switch and cook the motor.

As I was doing my exhaust tonight, I crawled under to see if that switch was leaking. on the passenger side, near the rear of the block, RIGHT above the panrail was another sensor/switch with nothing plugged in. It had the same round "single pin" style connector as the other one. What exactly is this item for? The wiring from the fan switch will also reach there so something might be plugged in backwards. This sucks without a service manual.

 

Stock fan switch temp - 238°
Pass. side head - Fan switch
Pass. side block - Knock sensor

 

hmmmm

didn't know they run knock sensors on carbed cars.

 

check the CTS on the front of the intake manifold. its a little plug going into the manifold with 2 wires i believe. mine was faulty and caused the fan not to turn on (CTS is coolant temperature switch, if u didnt know).

 

Thanks Mike. I'll check that out when I go out to the garage next. I do recall a connector on the manifold being wrapped in electrical tape.

Damn previous owner lol

 

oh my ***, the previous owner of my truck totally and i mean totally cut/slit and ran together with electrical tape, ALL OVER the place..

having troubles with my lights now due to a short somewhere and i cannot trace his wires cause one wire is 3 different colors due to 3 different wires taped together when like 60 feet of wire is only a few bucks... HAH

 

If that were bad the TC also wouldn't lock-up once at operating temp/closed loop and it will throw a code (SES light).
I'm not sure if 87 changed (doubtful though) but, the LG4 motor's ECM never had control of the fan anyways so, the CTS wouldn't make any difference http://www.deadbird.org/tech/ghfan.gif

 

well it's a 5-speed so that rules out any TC relation.

Without delving into it too much,, I'm thinking either a bad wire somewhere or the relay is acting wonky. Only thing is, if it was the relay, why does the fan still work in "A/C" mode?

It is bitterly cold up here right now so it's not that big of a concern, BUT, since the car is getting a ton of new parts, I'd rather take care of it now.

I guess I'm more old school then I though. I'm used to clutch/flex fans and all the non- sensor pre-87 sbc/bbc.