Amps drop when A/C is turned on...
Thread Starter
Intermediate
Joined: Mar 2002
Posts: 32
Likes: 0
From: Greer SC
Volts drop when A/C is turned on...
The volts drop to around 11.3-11.7 w/ the red light after I turn the A/C on.
Is it the battery, alternator, belt loose?
The red indicator will go off sometimes after I run the car a little bit but as soon as I idle, she's back on. Only happens when the A/C is pulling down the voltage.
Thanks for the help guys.
[Modified by Slingshot, 9:54 AM 6/20/2002]
Is it the battery, alternator, belt loose?
The red indicator will go off sometimes after I run the car a little bit but as soon as I idle, she's back on. Only happens when the A/C is pulling down the voltage.
Thanks for the help guys.
[Modified by Slingshot, 9:54 AM 6/20/2002]
Le Mans Master
Joined: Jun 2001
Posts: 5,419
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From: Are you the bug or are you the windshield.....
Re: Volts drop when A/C is turned on... (Slingshot)
What is the voltage that your car is pulling without the A/C on??????
What year is your car?????
Do you have a serpentine belt?
[Modified by Husker Vette, 8:56 AM 6/20/2002]
What year is your car?????
Do you have a serpentine belt?
[Modified by Husker Vette, 8:56 AM 6/20/2002]
Thread Starter
Intermediate
Joined: Mar 2002
Posts: 32
Likes: 0
From: Greer SC
Re: Volts drop when A/C is turned on... (Husker Vette)
1984.
I actually never checked the volts without the A/C.
I usually have the switch set to Water Temp when the indicator shows the voltage drop.
After driving a while or shutting the A/C off it will go back to showing Water Temp.
I actually never checked the volts without the A/C.
I usually have the switch set to Water Temp when the indicator shows the voltage drop.
After driving a while or shutting the A/C off it will go back to showing Water Temp.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: Volts drop when A/C is turned on... (Slingshot)
At idle speeds, the alternator cannot deliver its rated current and the battery then supplies current and the voltage will fall. When you get underway, the alternator will pick up the electrical load and charge the battery. Your idle speed may be too low. When the red battery symbol comes on, the alternator is not charging the battery.
Le Mans Master
Joined: Jun 2001
Posts: 5,419
Likes: 0
From: Are you the bug or are you the windshield.....
Re: Volts drop when A/C is turned on... (Slingshot)
The reason that I asked about the volts without the AC is because it could be a sign that your alternator is getting ready to go....
You should be pulling somewhere between high 13's and low 14's without the A/C while under normal driving conditions (not ideling).
As jfb pointed out when the red light comes on, it means that your battery is compensating for what your alternator can not provide..... I'm assuming that the red light comes on while under normal driving conditions, not just when stopped at a stop light..... Correct me if I'm wrong.
Take your car out for a drive, and flip the switch from Water Temp to volts and see what it says under normal driving conditions.
[Modified by Husker Vette, 10:53 AM 6/20/2002]
You should be pulling somewhere between high 13's and low 14's without the A/C while under normal driving conditions (not ideling).
As jfb pointed out when the red light comes on, it means that your battery is compensating for what your alternator can not provide..... I'm assuming that the red light comes on while under normal driving conditions, not just when stopped at a stop light..... Correct me if I'm wrong.
Take your car out for a drive, and flip the switch from Water Temp to volts and see what it says under normal driving conditions.
[Modified by Husker Vette, 10:53 AM 6/20/2002]
Burning Brakes
Joined: Sep 2001
Posts: 1,011
Likes: 0
From: Jupiter Florida
Re: Volts drop when A/C is turned on... (jfb)
At idle speeds, the alternator cannot deliver its rated current and the battery then supplies current and the voltage will fall. When you get underway, the alternator will pick up the electrical load and charge the battery. Your idle speed may be too low. When the red battery symbol comes on, the alternator is not charging the battery.
Another thought:
If the windings in the A/C clutch are breaking down it may be drawing a lot more current than normal, pulling the charging system voltage down. Might be worthwhile to put an ammeter in line with the battery and see what the current is with A/C on vs. A/C off.
[Modified by rocketfinger, 4:57 PM 6/20/2002]
Thread Starter
Intermediate
Joined: Mar 2002
Posts: 32
Likes: 0
From: Greer SC
Thanks guys...
I'll check the volts tonight while running down the road w/o the A/C.
The low voltage indicator comes on @ idle but remains on for @ least 2-3 minutes even after getting the engine up to speed. It does not go off immediately after getting the idle speed up.
I'll update tomorrow. Hope it's not the alternator getting ready to bail.
The low voltage indicator comes on @ idle but remains on for @ least 2-3 minutes even after getting the engine up to speed. It does not go off immediately after getting the idle speed up.
I'll update tomorrow. Hope it's not the alternator getting ready to bail.
Burning Brakes
Joined: Sep 2001
Posts: 1,011
Likes: 0
From: Jupiter Florida
Re: Thanks guys... (Slingshot)
Hope it's not the alternator getting ready to bail.
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Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Re: Thanks guys... (rocketfinger)
It isn't that difficult to replace the a/c clutch. Usually a bolt and a couple of snap rings. You will need to hold the outer hub to keep the shaft from turning and you can buy a special tool or use oil wrench pliers or a strap wrench to keep it from turning. Do check the blower motor leads for heat damage or if they're hot with the blower on high. GM blowers can pull a lot of amps and you may be dropping volts at the connector. If so, solder the leads to the connector. Also, check for a voltage drop at the ignition switch. You will need to drop the column to access it, but you want to verify that you have battery voltage on the output side. If not, some electric contact cleaner will reduce any resistance in the switch. At least I gained .2 volts by cleaning mine up. Also check the fan relay and the fan for voltage drop or an excessive draw. When it energizes and starts the motor, the draw will be at its highest, but it should drop back down. To check, simply disconnect it and see if there's any significant difference in your voltage.
Le Mans Master
Joined: Jun 2001
Posts: 5,419
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From: Are you the bug or are you the windshield.....
Re: Thanks guys... (Slingshot)
I'll check the volts tonight while running down the road w/o the A/C.
I'll update tomorrow. Hope it's not the alternator getting ready to bail.
I'll update tomorrow. Hope it's not the alternator getting ready to bail.
Let us know what yours is with and without the AC running, as Rocketfinger pointed out, it might be something to do with the AC Compressor and the windings.....
Le Mans Master
Joined: Jan 2002
Posts: 5,320
Likes: 4
From: Kyle TX (Because Mojo Made me fill it in)
Re: Thanks guys... (Husker Vette)
When it rains it pours. Just got my AC fixed today and I got the same problem now. Prior to the AC being fixed, I was pulling 13.8-14.1 while on the freeway. Now, Im pulling 11.7 with the AC turned off. With the AC on, it drops down to 11.2. The vette shop said that the extra load on the Alt from the AC pushed my Alt over the edge and toasted the already weak Atl. Im going to replace the stupid Atl and see how long that lasts.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Volts drop when A/C is turned on... (Slingshot)
I just replaced my alt with a rebuild Delco and had the overdrive pulley instaled to compensate for the underdrive crank pulley.
Now while idling at 600rpm in gear with the A/C on voltage is in the mid 13s. It never drops below 12s with all accessories on.
Definitely have the alt checked. BTW there's an article in the latest Corvette Fever on rebuilding an alt; of course I read it the day after I installed the rebuilt unit.
Now while idling at 600rpm in gear with the A/C on voltage is in the mid 13s. It never drops below 12s with all accessories on.
Definitely have the alt checked. BTW there's an article in the latest Corvette Fever on rebuilding an alt; of course I read it the day after I installed the rebuilt unit.
Le Mans Master
Joined: Jun 2001
Posts: 5,419
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From: Are you the bug or are you the windshield.....
Re: Thanks guys... (VetteNoob)
Vettenoob,
I got my alternator from Oreilly's.... it is a remanufactured with a lifetime warranty..... I remember reading sometime ago that 86's seemed to eat up and spit out alternators......
Just a thought.....
I got my alternator from Oreilly's.... it is a remanufactured with a lifetime warranty..... I remember reading sometime ago that 86's seemed to eat up and spit out alternators......
Just a thought.....
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Re: Thanks guys... (VetteNoob)
Could be and with low voltage with the a/c OFF the alternator is probably shot. You did post though that the ground wire from the blower motor (which is spliced into the module ground) had shorted. Something caused that to happen and my guess would be an excessive draw from the blower motor or a crummy connection that generated enough heat to melt the wire(s). You might want to check that out, especially if the shop only crimped the wire(s) to repair it. Heavy draw items should always have soldered connectors. Otherwise, it may happen again.
Le Mans Master
Joined: Jan 2002
Posts: 5,320
Likes: 4
From: Kyle TX (Because Mojo Made me fill it in)
Re: Volts drop when A/C is turned on... (Slingshot)
SLingshot I just replaced my alternator with one from O'Reily's Autoparts. It was $77 w/$45 core charge. They said it had a lifetime warranty for as long as I own my car. I specifically asked them if the original one I bought craps out in a year and if it was replaced under warranty, would the replacement one have a lifetime warranty as well. They said yes, I still have to take the core back, but Im gonna try to get that in writing. Just thought Id let you know where to get a cheap alt if you need one.
Thanks Husker on the heads up on where you can get one. Saved me some samolians :D !
[Modified by VetteNoob, 10:15 AM 6/21/2002]
Thanks Husker on the heads up on where you can get one. Saved me some samolians :D !
[Modified by VetteNoob, 10:15 AM 6/21/2002]
