Help with fan circuit

[kenthompson]

I am trying to find the location of the fusible link for the fan circuits. I have no power to one relay, and power to the other.

I'm thinking the main fan would work if it had power.

[gbrtng]

Originally Posted by kenthompson

I am trying to find the location of the fusible link for the fan circuits. I have no power to one relay, and power to the other.

I'm thinking the main fan would work if it had power.

All fusible links connect at the post behind the battery.
Check that the fan turns freely - I had one blow when a small rock
got between the fan outer ring and the radiator shroud. I couldn't
find the correct size link wire so used an inline fuse instead - 25 amps
I think - the motor pulls beaucoup start current.

Good luck,
Glenn
91-1341

[kenthompson]

Thanks,

That helps a lot.

After further research, putting the access key in the diagnostic port turns on one fan. Should it turn on both?

Is there a radiator fan sensor, or does the PCM go off the coolant temp sensor? If it's the coolant temp sensor, that's under the plenum right?

Thanks for the help.

[gbrtng]

Originally Posted by kenthompson

Thanks,

That helps a lot.

After further research, putting the access key in the diagnostic port turns on one fan. Should it turn on both?

Is there a radiator fan sensor, or does the PCM go off the coolant temp sensor? If it's the coolant temp sensor, that's under the plenum right?

Thanks for the help.

Not sure what you mean by access key, but when I hook up Gordon
Killebrew's code reader to the ALDL connector, both fans run. I think
the same thing happens with the TECH 1 too. Anyhow, both fans
should run when the AC is on; by that I mean the compressor
is running, cold air comes out of the vents, and the AC system
is healthy and fully charged. The signal to pull both fans on comes from
the ECM to the two relays on the left side of the radiator housing.
That signal is a result of the coolant temperature, the AC state and
several other variables such as vehicle speed. And then it gets
complicated ... Let us know what you find.

Glenn

[bldavis11]

Originally Posted by gbrtng

Not sure what you mean by access key, but when I hook up Gordon
Killebrew's code reader to the ALDL connector, both fans run. I think
the same thing happens with the TECH 1 too. Anyhow, both fans
should run when the AC is on; by that I mean the compressor
is running, cold air comes out of the vents, and the AC system
is healthy and fully charged. The signal to pull both fans on comes from
the ECM to the two relays on the left side of the radiator housing.
That signal is a result of the coolant temperature, the AC state and
several other variables such as vehicle speed. And then it gets
complicated ... Let us know what you find.

Glenn

Yep. Just turn the car on and then turn the AC on. Both fans should be running.

[kenthompson]

Ok,

The AC is not charged right now, so I don't know if the fans would turn on based on AC pressure.

The secondary fan does turn on when the forked key that I got at Autozone for the OBDI connector is plugged in.

I found the wire from the terminal block to the fusible link was melted, and burned in two. After replacing it with a fuse, it instantly blew the fuse when I plugged in the "key" to the diagnostic port.

Hmm, the plot thickens.....

When I take a direct lead from the battery to the fan lead, the motor sounds like it is full of marbles, and the wire gets REALLY hot REALLY quickly. I'm sure the brushes are toast in it.

Anybody had luck with aftermarket fan motors?

[gbrtng]

Originally Posted by kenthompson

Ok,

The AC is not charged right now, so I don't know if the fans would turn on based on AC pressure.

The secondary fan does turn on when the forked key that I got at Autozone for the OBDI connector is plugged in.

I found the wire from the terminal block to the fusible link was melted, and burned in two. After replacing it with a fuse, it instantly blew the fuse when I plugged in the "key" to the diagnostic port.

Hmm, the plot thickens.....

When I take a direct lead from the battery to the fan lead, the motor sounds like it is full of marbles, and the wire gets REALLY hot REALLY quickly. I'm sure the brushes are toast in it.

Anybody had luck with aftermarket fan motors?

You buy the fan and motor as an assembly from the Chevy dealer.
Aftermarket should be OK - the motors are probably made by one
OEM anyway. I'll bet this is a common part across all GM carlines.