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My cooling fans do not engage, with or without the A/C on.
Where can I locate the sensor for the fans?
Where can I locate the sensor for the fans?
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Re: 1995 Coupe LT1
Lee,
This is a common problem with those cars.
Does the A/C compressor engage? Does it cool when you are moving?
Have you checked the fan fuses?
If the fuses are good you can check the fan by wiring them direct to the battery.
The fans are turned on and off by relays controlled by the ECM (computer). I belive the relays are in front of the left front wheel mounted on the side of the radiator/fan package. Power is supplied to the relay and is grounded by the ECM to turn the fans on. You can check the relay by wiring the primary side to the battery and checking the secondary side to see if the circuit is completed. With no power to the primary side, the secondary side should be open circuit. With power to the primary side the relay should click and the secondary side should show a completed circuit.
If the fans work and the relays check out the problem is in the wiring, sensors or ECM. The ECM checks the engine temperature for normal fan operation and the A/C pressure and A/C request for A/C fan operation. So, you have at least two sensors, the wiring and the ECM as potential culprits. There are two engine temperature sensors, one for the gauge and one for the ECM.
So, you have a non-trivial diagnostics problem.
Some people give up and install a manual switch for the fans, wire the fans to an ignition switched source and wire to the A/C compressor actuator and bypass the ECM altogether. None of these are optimum but are options.
Verle -
Re: 1995 Coupe LT1
My experience is with LT1 in B & D-bodies, but after relays (one can swap relay from primary to secondary fan, and the fuel pump relay is also the same as the fan relays) the next culprit for fans that fail is the temperature sensor. B & D-bodies have separate sensors for the gage and the ECM, and some F-bodies have a combined (3-wire) sensor for both functions. I'm not sure which the Y-body has. On B & D-bodies the ECM (fan) sensor is on the water pump. I suggest you check your FSM (Factory Service Manual) for the sensor location and style as well as for the temperatures the fan(s) actuate at. You may be surprised at how high the temp has to go before the fan(s) come on. 230* comes to mind, but I can't recall if that is primary or secondary -- and Y-body may be different anyway.
You should find a trouble-shooting tree for this issue in the manual. Follow it and you will find your problem most expeditiously. Inspect the connections for the relays well. Occasionally corrosion or over-heating will make the relay connections problematic.
As Verle suggests hot-wiring to the fan motor will verify motor operation. If you chose that route be sure to include a 30a fuse in the line and use adequate size (I like #10) wire. Be careful because 30a is a lot of power.
I just thought -- a prime place for power loss to the fan(s) on B & D-bodies is a connector at the fan assembly where the power connects to the fan(s) from the body. I don't know if Y-bodies have the same connection, but I would bet on it. Makes putting the car together easier. Check fan(s) ground also.TerryComment
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Re: 1995 Coupe LT1
I had the occasion to trouble shoot a 94 with the same problem.
Fans checked out, relays worked and had power to the secondary side. Activated the fans through the relays by jumping the primary side of the relays. Activated the fans by grounding the primary side ground with the engine running.
The ECM temp sensor on the water pump checked out but replaced it anyway.
A/C worked. A/C pressure sensor checked out.
Checked all connections for loose wires, corrosion, good connections.
Replaced the ECM with known good ECM.
Nothing made the fans go.
Owner decided on a manual switch from a switched source.
I didn't like it, not a good solution but I didn't have a better one at the time.
VerleComment
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