1989 Camaro RS 305 TBI 101,000 milies

My engine recently got super hot, not to the overheating point but to where the needle was almost on the red. I pulled over and shut off the car to notice that in the coolant resovour, was coolant bubbling. so i turned the ignition on to let the fan turn on because obviously the engine was way over the 200? where the fan kicks on. and the fan wouldnt turn on. so i let the car sit for several hours to cool down. later i replaced the thermostat with a 160?and i ran it again with it hooked up to a scanner, and a digital read out of the coolant temp. I let it idol for quite a bit of time untill the coolant reached 225?. The fan never kicked on! I let it cool and checked all my sensors on the block and they are all hooked up. no bad wires either. And the fan was just recently working fine because i was timing the engine and it kicked in normally. I checked all the wires and they are all good and all the sensors. Everything appears to be good. HELP

 

I bet the temp sending switch is bad. Just because it is hooked up does not mean it is working.

 

By switch you mean sensor? or maybe a Relay? The sensor located on the intake manifold next to the thermostat? Or the one on the driver side head? because it hooked it up to a scanner and it gave me an accurate and digital coolant temp, as well as the gauge in the car, so how can it not be working??

 

Probably the coolant fan switch on the passenger side of the block.

 

I believe that the temp sensor in the driver side head is just for the temp gage in the car, it doesn't send input to turn on the fans. The CTS (Coolant Temp. Switch) does this and is located in the front of the motor. Also check the fan switch as also mentioned. Its located between the #6 & #8 spark plugs. One more thing, I believe the actual turn on temp is more like 227 degrees and don't rely on the temp gage in the car, because they are not accurate.

Hope this helps.

 

Description and Operation

The electric cooling fan is used for both the cooling system and the A/C condenser. The fan is controlled by the ECM. The ECM will ground the cooling fan relay, which turns "ON" the fan when the following conditions are met.

Coolant temperature sensor(CTS) signal indicating a temperature greater than 106°C (222°F).
A/C head pressure greater than 233 psi and vehicle speed less than 40 mph.
When the cooling fan is turned "ON" it will stay "ON" for a minimum of 15 seconds.


Computer Command Control - Throttle Body Fuel Injection
Coolant Temperature Sensor (CTS)

The engine coolant temperature sensor is a thermistor that is located in the engine coolant flow. When the coolant temperature is low, the sensor produces a high resistance. When the coolant temperature is high, the sensor produces a low resistance.

The computer sends a 5.0 volt signal to the coolant temperature sensor through a resistor in the ECM and measures the voltage. The voltage will be high or low depending on coolant temperature. By varying the voltage, the computer will sense engine coolant temperature.
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Description and Operation

COOLANT TEMPERATURE FAN SWITCH(on passneger side under exhaust manifold also called auxilary switch)

This switch regulates voltage to the coolant fan relay, which operates the fan when the engine coolant temperature exceeds 116°C (243°F).
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Description and Operation

Temperature gauge sending unit (loacated on drivers side under exhaust manifold)

This temperature indicating system consists of a sending unit, located on the cylinder head, electrical temperature gauge and an instrument voltage regulator. As engine temperature increases or decreases, the resistance of the sending unit changes, in turn controlling current flow through the gauge. When engine temperature is low sending unit resistance is high, current flow through the gauge is restricted, and the gauge pointer remains against the stop or moves very little. As engine temperature increases sending unit resistance decreases and current flow through the gauge increases, resulting in increased pointer movement.
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Just my .02$, read a few post's here lately and everyone has different idea on what does what. So here's some pulls right out of maint. manuals for a 89 RS with a 305 and A/C.
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Now from original post , it sounds like you have a fan problem or relay problem. If the auxiliray switch (under passenger side exhaust) did not kick it on. Then you did not have power to the fan when it got really hot.

So then what you can check quick to find problem

-wire to aux switch not hooked up (this has to be hooked up for fan to work the ecm as well....it is in the ecm circuit some how)

-make sure you have power at fan relay (pull relay out of socket, it is on the drivers side firewall, outside of brake booster ) Use a test light or meter to see if you have 12 volts at pink or red wire) If so move to next step

-fan motor is smoke checked (to check it just pull releay out of socket on drivers side on the fire wall and use a jumper wire to the black/red and pink wire's. If fan dont come on replace motor if it does look at relay)
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Hope this isnt to long winded and should at least help several other post's on what switch,sendor, controller does what.