Voltage drop at idle with AC on.
08-28-2018, 07:59 PM
#1
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Car: 87 T/A
Engine: 305 TPI
Transmission: 700R4
Voltage drop at idle with AC on.
I have an 87 Transam 305 TPI. When I have the air on I am getting a voltage drop at idle to about 20 or 11 volts. The voltage goes back to 13 as soon as the car comes off of idle. The alternator and battery check out as OK. I have replaced the blower motor and resistors. It seems like maybe the idle isn't going up like it should when the air is turned on.
My question is what controls this or what else could be causing the voltage to drop.
Any help would be greatly appreciated.
My question is what controls this or what else could be causing the voltage to drop.
Any help would be greatly appreciated.
09-04-2018, 05:42 PM
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Car: LOWERED ♦ CRIMSON METALFLAKE
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Alternative Advice
Originally Posted by TABBOO
It seems like maybe the idle isn't going up like it should when the air is turned on.
Connect one and observe.
If the idle goes below 600 many alts will turn off.
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09-04-2018, 11:04 PM
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Car: 87 T/A
Engine: 305 TPI
Transmission: 700R4
Re: Voltage drop at idle with AC on.
I have a working tach.The voltage drop only occurs at idle when the idle goes from its cold idle around 750 rpm in drive with foot on brake to the normal 550 rpm. I think the problem is that when you have the air conditioner on the computer is supposed to boost the idle to 750 rpm. My car isn't doing that. What I wonder is if there might be a relay or something not working.
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