Hi gang,
My gf's 91 Camaro will overheat if it sits in traffic. The cooling fan never turns on. The fan will turn on if you turn the AC on, which you would expect. Do you know if you can turn the fan on manually with a code scan tool? Thanks for your time,

Cam

Its been a few hours since you posted so let me give this a stab. In short I don't know if a scan tool will turn the fan on or not. I do know that most likely depends on the scan tool. The 3rd gen camaros could energize the fans via the diagnostic terminal. I would presume that 91s would also. It's just that some scan tools are only good for reading codes and a few parameters. Others will let you enter factory diagnostic modes and all sorts of stuff. I'd start troubleshooting by getting a schematic and tracing through the fan circiutry.

-dnult

Yeah, I've traced it out on the schematics and all that is there is a relay whose pick coil is driven by the computer. If the fan didn't turn on with the AC, I'd expect that maybe the relay, fuse or the fan was bad but because the fan turns on with the AC,I'm a bit stumped. I only see one temp sensor and the gauge works so I'm assuming (I know, I know) that it detects the temperature right. Maybe there are two sensors......... hmmmmmmm......

Thanks,

Cam

Originally posted by Cam Sweet:
Maybe there are two sensors......... hmmmmmmm...... There should be two sensors. In fact, the computer temp sensor should have two wires connected to it - signal and return. The guage senders are signle wire with return through the block. It amazes me how some of the published schematics leave you guessing at those important details. I believe the CTS for the computer is in the intake manifold near the thermostat housing.

-dnult

this thing TBI, TPI or V6???

the TPI cars have 2 fans... the others have a single fan...

on the single fan cars the fan is turned on via the ECM...

on the TPI cars there is a switch on the pass side of the block for one fan and the other is controlled by the ECM I believe...

Originally posted by zroc:
...on the TPI cars there is a switch on the pass side of the block for one fan and the other is controlled by the ECM I believe... Zroc, TPI sounds like a three sensor system. 1 for the ECM, 1 for Fan 1, and the third for the guage. Right?

-dnult

Thanks Guys,
It's a 6 cylinder TPI. I'll chase the schematics out a bit more.

Cam

Originally posted by dnult:
</font><blockquote>quote:</font><hr />Originally posted by zroc:
...on the TPI cars there is a switch on the pass side of the block for one fan and the other is controlled by the ECM I believe... Zroc, TPI sounds like a three sensor system. 1 for the ECM, 1 for Fan 1, and the third for the guage. Right?

-dnult </font>[/QUOTE]yeah... sorta... the one for the guage is just like any other elec guage sender... called a thermistor or sumthin of the like...

the CTS (coolant temp sensor) is seperate and sends a voltage signal to the ECM... its also a thermistor

if this car has A/C it will have a pressure switch to turn the fan on when the a/c is running...

otherwise the fan is controled by the temp reading the ECM gets from the CTS...

all power to the fans of these go though a relay...

eh... food for thought...