Re: re: Help - a/c & idle

["Paul C. Waterloo" <74543.407@compuserve.com>]

>- - 90% of the time, car at idle, turn on a/c, idle stays
>constant (800-900rpm). - - after car has been in stop & go
>traffic for about 15-30 minutes, the idle suddenly drops to
>about 500rpm.  Turn of a/c, idle is fine.  Turn back on, idle
>goes to 500rpm (car shakes very badly). - - after car has been
>turned off and sat for awhile, start car, run a/c. Idle is
>fine.

>*Something* either temperature or time-related seems to destroy
>the signal to compensate the throttle for the additional a/c
>load on the engine.  ISV is only about 6 months old.  No
>apparent vacuum problems.  No other symptoms.

>I would appreciate any ideas....thanks everyone.........SLM

I would start by finding out what switches on the signal to the fuel injection
system that the compressor is on. Is it when the clutch gets engaged by a
solednoid or something? Find out what this is, then put a multimeter on it.
Should have a 12 volt signal on it with the clutch engaged, and zero when it is
not (or whatever triggers it on). 

Then recreate the problem. Measure the voltage, and record what is normal for
normal operating conditions. Heat the engine up and wait for the engine not to
speed up, do you still have the correct signal? If not, you know it is in the
clutch switch or some other component up stream in the circuit. I bet it is a
high resistance connection (either a bad switch or a corrodded connector). If it
is, when its problem is temperature effected. When the ambient gets hot, it's
just enough to throw it over the edge.

Good luck!

Paul

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Paul Waterloo
Riverside, IL

91 200q

EMAIL: 74543.407@compuserve.com
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