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Trouble with engine idle
Posted: Wed Jan 07, 2004 7:58 pm
by Impulsive
Hi all,
I have a 1994 Sierra. I know that they have a small alternator, but I was wondering what could be causing my idle to go from the normal 750, up to about 1200 - 1300 when I switch on the blower fan inside the car.
It doesn't matter what speed it's on at. It just has to be on.
The car is fitted with air conditioning, but I don't have to have the air on for this to happen.
Any opinions are appreciated.
Posted: Sun Jan 11, 2004 8:24 pm
by Bluey
i know some cars increase idle when air con turned on, possible that this is the case in sierra when fan on??? ie to compensate for small battery (or maybe heaps of other accessories eg family car) then turning air con/fan? automatically ups idle speed therefore delivering higher voltage to keep everything going.
Electrical Issues
Posted: Tue Jan 13, 2004 4:54 pm
by Impulsive
Yeah, I guess it could be. The small battery theory makes sense.
I'll check a couple of other sierras to see if they do the same. Thanks for your reply.
Posted: Wed Jan 14, 2004 7:23 am
by murcod
Ferozas have a solenoid that opens to increase the idle when the fan is on (but they are EFI too....) Perhaps there's a similar thing with your Sierra's carby set up????
Re: Trouble with engine idle
Posted: Wed Jan 14, 2004 2:57 pm
by mkpatrol
Impulsive wrote:Hi all,
I have a 1994 Sierra. I know that they have a small alternator, but I was wondering what could be causing my idle to go from the normal 750, up to about 1200 - 1300 when I switch on the blower fan inside the car.
It doesn't matter what speed it's on at. It just has to be on.
The car is fitted with air conditioning, but I don't have to have the air on for this to happen.
Any opinions are appreciated.
Your A/C can be switched on & off with the A/C switch as well as the fan switch. Your A/C will actually swicht on & off with the fan switch to protect the system from overheating. I would say the main A/C (the one with A/C written on it) may be faulty & when you turn the fan on the A/C automatically comes on causing your idle up solenoid to operate.
The other way this can happen is the relay which operates the idle up solenoid is recieving a false reading from the fan switch when it is switched on.
See an auto electritian, they will be able to help