Fan not turning on when temperature hot enough to turn it on
I'm new here and am excited to be in touch with others concerning Z28. I bought mine new in 1986. Iroc Z28 TPI 305. Ran the OBD check and the fan comes on when going through it's system check. Figure the relay and motor are not the problem but a sensor issue. I read that a sensor is located on the passenger side back between the 2 cylinders. Mine does not have one located there but there is a plug screwed into where the hole would be for one. After further research I read that a coolant sensor is located on the front of the intake manifold next to the cold start sensor for the fuel injection. Is this coolant sensor actually connected to the ECM to tell the fan to turn on when the coolant reaches temperature.
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Re: Fan not turning on when temperature hot enough to turn it on
I'm no expert on this, but I think you are correct about the sensor on the front of the intake manifold. That one connects to the ECM. There is also supposed to be a redundant sensor that directly controls the fan relay (in a backup mode). It is reportedly at the lower right hand side of the engine. I believe the temp for the redundant sensor is 240F.
The sensor on the right side between the cylinders is only on the carbed G engine. |
Re: Fan not turning on when temperature hot enough to turn it on
Thanks for the reply. I checked further about a another sensor on the right hand side. The only other sensor in that area is the knock sensor located on the block just above the starter. I'm going to replace the one on the front that I mentioned and see if that allows my fan to come on.
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Re: Fan not turning on when temperature hot enough to turn it on
With a dual fan set up, the left side fan is controlled by the ECM and right side fan is for the A/C and is run off a fan switch on the rear of the passenger head. The right side fan ONLY comes on with the A/C and a head temp of 230/240deg.
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Re: Fan not turning on when temperature hot enough to turn it on
Originally Posted by STR FTR 1
(Post 6966708)
I'm new here and am excited to be in touch with others concerning Z28. I bought mine new in 1986. Iroc Z28 TPI 305. Ran the OBD check and the fan comes on when going through it's system check. Figure the relay and motor are not the problem but a sensor issue. I read that a sensor is located on the passenger side back between the 2 cylinders. Mine does not have one located there but there is a plug screwed into where the hole would be for one. After further research I read that a coolant sensor is located on the front of the intake manifold next to the cold start sensor for the fuel injection. Is this coolant sensor actually connected to the ECM to tell the fan to turn on when the coolant reaches temperature.
The fan is supposed to come on when you are checking for codes or in diagostic mode. LOL |
Re: Fan not turning on when temperature hot enough to turn it on
Originally Posted by birdman11
(Post 6971769)
The fan is supposed to come on when you are checking for codes or in diagostic mode. LOL
I'm pretty sure he knows that, and stated it only to verify that the control circuits and power supply for the fans were obviously intact and functioning. That pointed him to the sensor, which is what he asked about. |
Re: Fan not turning on when temperature hot enough to turn it on
I am having the same trouble with my 1991 Camaro. I would like to know where
exactly the relay is for the fan switch. I had the switch replaced (or so the mechanic said) and now I am looking at replacing the relay. Anyone know where it is? |
Re: Fan not turning on when temperature hot enough to turn it on
Which engine do you have? Do you have A/C? Do you have dual fans?
The single fan relay is typically on the firewall, between the brake master/booster and the fender. The fuel pump relay is also there. |
Re: Fan not turning on when temperature hot enough to turn it on
Originally Posted by Injuneer
(Post 6995825)
Which engine do you have? Do you have A/C? Do you have dual fans?
The single fan relay is typically on the firewall, between the brake master/booster and the fender. The fuel pump relay is also there. |
Re: Fan not turning on when temperature hot enough to turn it on
Relays are fairly reliable components. Not aware if the 3rd Gens had any unusual problems, but I don’t know the 3rd Gens all that well.
If you are asking which of the two relays is for the fan: Coolant fan relay (controlled by ECM): 4 wires - Black/red Brown Dark green/white Orange Fuel pump relay: 5 wires- Red Orange Gray Black/white With dual fans, there is also an Auxiliary Coolant Fan Relay, controlled by the aux fan switch: 4 wires - Black/pink Gray Orange Brown |
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