A/C Drag
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Joined: Apr 2010
Posts: 58
Likes: 8
From: Lebanon TN
A/C Drag
When I turn on my A/C it drags the engine down too much. Tested the battery with A/C on and off and it dropped big time when A/C was on. Guy told me it was possibly the alternator not being able to handle the load. Looked up the specs the guy who restored it sent to me and he has a "200 amp GM alternator and wired as per MAD -electrical recommendations" on it. Would that sound like the alternator is going out, or more not strong enough. The battery is new and tested fine.
Any suggestions on what I would need. Would like to run the a/c while driving, especially since it's black.
Any suggestions on what I would need. Would like to run the a/c while driving, especially since it's black.
Burning Brakes
Joined: Aug 2013
Posts: 1,071
Likes: 322
From: palm springs ca
I would also consider that the system may be overcharged with gas. Only 2 electrical items in the system and haven't heard of a HD compressor clutch, but do know he blower motor is stronger. Also there is a third electrical item that may not be working and that's at the carb to boost up the idle when the A/C is selected.
Dom
Dom
Le Mans Master
Joined: Jun 2019
Posts: 7,670
Likes: 2,476
From: Indiana
what is your car? year and manual or auto..mods..
is it not keeping up volts at idle? how are you measuring? if you have a 79 manual (as your picture has 79) then there is no solenoid to increase idle rpm when ac on.. but idle is 900rpm..
200 amp alternator kinda scares me unless wiring all upgraded? any pics alternator etc..?
is it not keeping up volts at idle? how are you measuring? if you have a 79 manual (as your picture has 79) then there is no solenoid to increase idle rpm when ac on.. but idle is 900rpm..
200 amp alternator kinda scares me unless wiring all upgraded? any pics alternator etc..?
Last edited by interpon; Mar 9, 2021 at 08:29 AM.
Race Director
Joined: Mar 2017
Posts: 11,960
Likes: 4,518
From: Virginia
Black 79s are favorite.
The guy who restored your car told you the alternator was the problem when you run the A/C? Due to extra electrical load? What happens when you turn on the headlights?
The drag would come from the A/C compressor. I agree that the system is possibly overcharged. You can also look for vacuum leaks that can change the idle mixture of your engine. I yanked A/C out of my 80, and I haven't made it work yet in my 79, but some HVAC controls run on vacuum. Certainly the coolant bypass valve for the heater core, and some of the other directional doors in the HVAC system.
What is your timing set to?
The guy who restored your car told you the alternator was the problem when you run the A/C? Due to extra electrical load? What happens when you turn on the headlights?
The drag would come from the A/C compressor. I agree that the system is possibly overcharged. You can also look for vacuum leaks that can change the idle mixture of your engine. I yanked A/C out of my 80, and I haven't made it work yet in my 79, but some HVAC controls run on vacuum. Certainly the coolant bypass valve for the heater core, and some of the other directional doors in the HVAC system.
What is your timing set to?
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
There is an idle kick solenoid that holds the throttle at a higher setting to offset the load of the ac compressor.
it won’t push the throttle , just hold it once the throttle has been deflected.
yours may be missing or not functioning correctly.
https://www.ecklerscorvette.com/lect...SABEgLGC_D_BwE
it won’t push the throttle , just hold it once the throttle has been deflected.
yours may be missing or not functioning correctly.
https://www.ecklerscorvette.com/lect...SABEgLGC_D_BwE
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Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
How hard is the compressor to turn by hand? Not the pulley, but the drive.....grab it and spin it, it should have some resistance but not too much.....
The A/C solenoid mentioned above could be part of the problem along with timing being too retarded.
Jebby
The A/C solenoid mentioned above could be part of the problem along with timing being too retarded.
Jebby