B18C1 in 1990 DA

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ej1times

Junior Member
I had a question that I was hoping you guys could answer for me. My brother has a B18C1 in his 90 DA and when he turns on the A/C hi idle goes down to practically 100rpm. When the car is warmed up idle is at around 1000rpm. Any info would be most appreciated. Thanks.
 
that sounds like time for a new battery/alternator. the increased draw from the A/C compressor can do that to a motor.
 
or bad compressor bearings, but then you'd prolly have a loud screeching noise too. As I recall, the ac compressor doesn't draw current, it is belt driven. I think that when the ac is on, is creates a vaccuum on the system, and that causes the motor rpm to increase, kinda like when you pump your brakes. I dunno exactly how it works, but that's my best guess.
 
yeah its belt driven, but the power has to come from somewhere, the alternator/battery.

and the bearings might account for the raised RPMs but not the lower ones.

take it to your mechanic and have him do a draw test on the alternator A/C compressor and battery.
 
Actually, the a/c is not powered by electricity at all. Its compressor is belt driven. It it was driven by an electric motor, it would not need to be belt driven. The only thing that is connected to electricity is the compressor's magnetic clutch, and I can't see that thing frying. Check it anyway, does the car bog specifically with the a/c on, or is it if you use the fan? I have heard of the fan blower motor going out and sucking all kinds of current.
 
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