[Shotimes] Overheat - Part II

[Adam Parrott]

Steve,

At least in the case of your delayed fan-on problem, I'd be willing to bet
that your (relatively new) ECT sensor is to blame.  The EEC uses the
readings that it receives from the ECT sensor as it's primary determinant
for deciding when to operate the fans.  If the ECT sensor is inaccurate in
it's reporting of the coolant temperature, then fan operation can and will
be affected, possibly leading to engine damage if not caught.

As for your other Q, the EEC will not operate the fans while travelling at
highway speeds unless the coolant temperature (as reported by the ECT
sensor) has risen above a certain specified point (at which point it will
turn them on and attempt to cool the coolant down, regardless of speed).

As for the rest of your cooling problems, I'd have to side with the others
here and say that your radiator is most likely to blame.  Replace that suck
and hopefully you won't have to replace anything else!

Adam


----- Original Message ----- 
From: "Steve Tatro" <stevetatro_shotimes@earthlink.net>
To: <rob.pittman@verizon.net>; <shotimes@autox.team.net>
Sent: Friday, July 30, 2004 4:35 PM
Subject: Re: RE: [Shotimes] Overheat - Part II


Thanks Rob.  Hope you don't mind me replying to this to the list, just so I
can get maximum input!

I just did a bit more troubleshooting (at least as much as my peabrain will
allow).  Engine cold, started it up, EATC "OFF".  Let it get warm,
thermostat opened, allowing upper radiator hose to get hot.  EATC still
"OFF".  The fans never kicked on.  Temp gauge needle up past "N" in NORMAL,
still nothing.  Turned the EATC to "MAX A/C" and the fans (both of them)
kicked on immediately.  Temp gauge needle continued to rise!  After a few
minutes I turned the EATC "OFF" again, and the fans remained running for a
few minutes, and the engine cooled down.  Once the needle got down to the
"R" in NORMAL, the fans shut off.  EATC still off, the engine started to
warm up again.  Got past the "N" again, and the fans never kicked on
automatically.  Shut the car down.

So, here's what I *assume*.  The fans work properly, seem to be spinning
freely (I was able to turn them both by hand), but something's not telling
them to turn on when they need to.  Is this yet another bad ECT sensor
(two-wire)?  Mine's only a few months old, although just a cheap plastic
NAPA part.  Or is this a faulty IRCM?

Also, another question.  Even without the fans working, shouldn't the flow
of air at highway speeds be enough to keep the car cool?  It's *better* on
the highway and gets much worse as I cruise around town, but it just
doesn't seem right.  Do the fans even run at highway speed?

It seems like something's still wrong with the radiator, since even with
the a/c on and the fans running the car won't stay cool.

Thoughts?

Thanks to everyone for all the help.

If anyone has any more specific diagnostic tools for me to try I'd
appreciate it.  I'm sorta guessing at this point!

Steve Tatro
Red/Black '93 with 178k miles
Monroe, Ohio

P.S.  List of recently replaced parts: ECT, gauge temp sender, thermostat,
radiator cap, chemical coolant flush, door striker bolt bushing ;^)

-----Original Message-----
From: Rob Pittman <email address removed>
Sent: Jul 30, 2004 4:56 PM
To: Steve Tatro <stevetatro_shotimes@earthlink.net>
Subject: Re: RE: [Shotimes] Overheat - Part II

Steve, there are two sensors in the cooling system.  Since you've replaced
them both, you should be in good shape.  The IRCM (Integrated Relay Control
Module) is the "black box" on the driver's side up next to the radiator.
It's under the plastic panel that covers the top of the radiator.  If you
trace the wires from the fan, you'll run right into it.  It should be
putting out something like 12 volts.  I'm on my third or fourth one now.
My alternator was overcharging, and it was a while before I figured it out.
In the interim, I think I must've fried a couple of the things.  The
two-wire sensor goes to the IRCM, and the one-wire to the temp gauge (or
vice versa, hell, now I'm confused...)  You've replaced them both, and I've
never heard of one going bad anyway.

Turn on the A/C while the car is cool.  Does the fan come on?  If not, then
unplug the fan (the wiring harness leads right to the IRCM), and check the
voltage at the IRCM end of the fan plug.  You should get a reading.  If
not, then I'd suspect the IRCM has gone bad.  If you get a voltage reading,
then suspect the fan motor is out.  Apply 12V to it and see if it runs.

The only other thing I can think of is the thermostat.  But I recall you
saying you changed it.  When it opens, you should be able to feel coolant
flowing through the hoses.

All this is gen 1 stuff, with a single speed fan, but the two speed fans
should operate in a similar fashion.

Are you in the D/FW area by any chance?
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