The other day my car was overheating. I found out the fan did not turn on when the engine temp hit 220 like it was supposed to.
However, the fan DID turn on when I engaged the A/C.

Replaced the coolant temp sensor, problem still there. ECM voltage and wiring checked OK.

Any suggestions?

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92 Camaro RS, LO3, 5-spd, T-tops

Performance:
K&N Open Air Filter, Edelbrock performer TBI intake, Fastchip Prom, Timing +4 degrees, Centerforce clutch, Xact 8mm wires, SLP 1 3/4" Headers (coated), Flowmaster Catback Exhaust, Richmond 3:42 gears, Torsen HD Posi
Sights & Sounds:
Alpine 8030 Alarm System, Valentine One Radar Detector (How did I ever drive without one?), Pioneer DEH 7450 Head Unit w/6-pack CD changer, Pioneer DEQ 7600 Sound Processor, 2 Kenwood KAC-846 Amps powering 2 12" Pro Red subs, 2 Pioneer 6x9 and 2 MTX 4x6 speakers. Z28 grille w/aftermarket lights, MacEwen whiteface gauges
NEXT UP: TBI & Suspension mods

 

you probably need to replace the fan switch sensor. Its on the passenger's side of the block by the knock sensor.

-=-Mike

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1989 RS.. 355, Hypereutectic pistons, double roller cam, double roller timing chain, accel wires, blue streak cap and rotor, rapidfire plugs, chevy caprice 350 chip, 200* fan switch, 3 angle valve job, 3 inch cat-back exhaust, 3 core radiator, 3.73 gearing with POSI.

 

That's what I suspected, but isn't the relay back near the firewall on the passenger side?

 

First your fan come's on at over 220* If it came on with the A/C switch, then your relay is good, but your fan switch could be weak. It is in back of the pass side head.

 

Can anyone describe what it looks like or what color wires run to it?

Thanks!

 

just wire it up to a toggle


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86 berlinetta
350cui w/.30 over
.526 hilift cam
hooker supercomps
3" duals
edelbrock streetmaster
holley 750 dp
bad asshauler

 

There's only two 1-wire sensors on the passenger side, the lowest (right above the pan rail)is the knock sensor, the other is the fan switch.
I bypassed mine altogether.
I'm now using and adjustable fan switch, with the thermocouple in the upper radiator hose,I can set the fans to come on at any temp I want.
Only cost about $25, which is less than a new factory-type fan switch.
-Rich-

 

I got the same system for my sc.I love it in the summer just turn the **** and the fan kicks in earlier and in the winter make it come on later.

 

I had the same problem a month ago. I first replaced the temp sensor (bottom of block on passenger side-single wire). Turned out that wasn't it because fan still wouldn't come on even with A/C on. Turned out to be fan relay switch. This is located on Driver side of firewall. There are 2 black boxes next to each other, it is the one closest to the fender. This would probably be your probem. Let me know if this helps.

Mark

 

the coolent fan switch is located in between the 6 and 8 plug, just under the manifold

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Trent
---Car---
89 Firebird/305 L03 TBI A4/t-tops
Open Element Edelbrock Aircleaner w/ K&N air filter/Summit Chrome Valve Covers
Edelbrock TES headers 3" out/flowmaster American thunder 3" exaust/Catco cat
---Stero---
Pioneer DEH-P730 Premium
Infinity 2way 4652 4x6's/Pioneer 4way ts-a6985 6x9's
profile cl640 110x4

 

One thing you need to be cautious of if you have to replace the coolent switch is the conector. Because the switch is so close to the manifold the plastic cover of the connector becomes brittle. The only way to remove it is by sqeezing the sides together. When I went to replace mine it crumbled to dust and my car has very low miles. Chevy is aware of this problem and keeps plenty on hand, i believe I payed around $15 for a new one.

Mark

 

I just got threw installing some new heads and i'm having the same problem with my fans not cutting on @ 220. I replaced the fan switch with a new sensor and connector. One thing I did notice is that when I unhook the coolant sensor under the t/b the fans stay on as soon as I start the car.

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1991 Z28 5.7L
All free mods/afpr/hurst lock up harness/flowmasters(off)/lakewood Lca's/accel stock size injectors/msd6A-plugs, ignition coil/k&n/lakewood adjustable panhard rod.
1/4mile 13.7@102. Expected et next outing 12.9@? (with slp 1 3/4 headers and new ported sportsman II heads along with 24lb injectors, adjustable torque arm spohn or bmr)

 

I think it's a green/white with a round connector.

 

Thanks for the replys fellas, it is the green and white wire....turns out it came loose so I managed to wedge it back in and the fan works fine.

I'll probably install an adjustable switch later on.