Fan not turning on when temperature hot enough to turn it on - CamaroZ28.Com Message Board


3rd Gen / L98 Engine Tech 1982 - 1992 Engine Related

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Old 08-04-2014, 06:18 PM   #1
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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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Old 08-04-2014, 10:07 PM   #2
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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.
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Old 08-05-2014, 10:55 AM   #3
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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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Old 08-06-2014, 04:23 PM   #4
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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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Old 01-01-2015, 11:36 AM   #5
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Re: Fan not turning on when temperature hot enough to turn it on

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Originally Posted by STR FTR 1 View Post
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
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Old 01-01-2015, 12:16 PM   #6
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Re: Fan not turning on when temperature hot enough to turn it on

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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.
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Old 12-04-2017, 05:29 PM   #7
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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?
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Old 12-05-2017, 01:24 AM   #8
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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.
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Old 12-05-2017, 08:35 AM   #9
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Re: Fan not turning on when temperature hot enough to turn it on

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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.
I have the 305ci. And yes on the A/C. Is this a normal occurrence for this part? I've already replaced it once last year. And which one is the relay?
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Old 12-05-2017, 08:17 PM   #10
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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 donít 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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