radiator fan comes on as soon as I turn on the ignition & A/C operation

Ed Kellock ekellock at gmail.com
Mon Aug 20 14:06:43 EDT 2007

After writing up this post, I decided to head down to the parking
garage for a little bit more diagnosis.

First I pulled the 2nd stage relay, started the engine, and then
turned on the A/C to confirm the low speed fan runs.  It does.

Then I turned the A/C OFF, replaced the 2nd stage relay, turned on the
parking lights on and pulled the "city light" bulb so I could see in
there which enabled me to see so I could disconnect the A/C high
pressure switch and the fan turned off.  I hope this just means I have
a bad high pressure switch.  I'll bet I will have to get the system
evacuated before changing the switch to avoid venting vapor gold to
the atmostphere, right?

This all came about Saturday when it was hot here and I was
stop-and-going around town and the A/C just didn't seem to be working
that great, which just seemed a function of the temperature and the
low speed, stop-and-go driving I was doing.  By the time I got home
the temp gauge was up the the higher thick mark so I left it running
to get out and see if the fan was running; and it was running on 2nd
speed.  I turned off the A/C and turned up the temp to HI and the car
cooled off, but the fan kept on running.

At this point, I wonder if I just have a failed high pressure switch
that got tripped and won't release, or if I probably need some A/C
service as well.


On 8/20/07, Ed Kellock <ekellock at gmail.com> wrote:
> This just developed on Saturday.  The radiator fan comes on as soon as
> I turn on the ignition and stays on until I turn it off, regardless of
> temp.  It runs at the 2nd speed (1st according to Bentley).
> I searched out some info on this, but didn't find an exact hit.  I did
> some of the diagnostics I found and I believe I have verified that it
> is not the temp sensor on the radiator.  I disconnected that and the
> fan stayed on.
> I also pulled both the relays for 2nd and 3rd speed and swapped them,
> no difference.
> The fan stops when I pull the 2nd stage relay and starts as soon as I
> put either of the 2 relays back into the 2nd stage location.
> I pulled the 2nd stage relay and let the car idle and the 3rd stage
> does activate when it should.
> The fan spins freely. and doesn't make any bad noises when it's running.
> I believe the after-run function is separate, but I did find that fuse
> 21 was blown.  I replaced it and did not get after-run function.  I
> did not get back to it after the car cooled down to test by shorting
> the two after run temp sensor wires together.
> From what I've read so far, it seems like the failure of the 3
> position resistor panel causes the fan to run even when the ignition
> is off.
> I also think I should find and disconnect the a/c high pressure switch.
> Any other ideas?
> Thanks,
> Ed

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