A/C, Voltage, Idle

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Apr 3, 2019 | 08:41 AM

haze324

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A/C, Voltage, Idle

Hey guys. Recently my battery died while out on the road to the point that jumping the car wouldn't fire it up. I figured the Alternator crapped out so I ordered a new alternator from Summit (100amp) and picked up a new battery at Advanced Autoparts and all was good to go. I've noticed the last few days that my A/C is FREEZING cold. I mean it's incredibly cold...colder than it's ever been.

Worried that my voltage will drop again I've been keeping my eye on the dash volt meter while driving. When I first put the alternator in I checked the battery with a digital multi meter and it sat at 12.7v, I turned the car on and in park it was a 13.5. What I noticed today based on the dash gauge in park it's just over 13v, in Drive with a little lower RPM's it's just at 13v, when I turn the A/C on it dips well below under 13 closer to 12 and slowly starts dipping toward 8-10v window. I rev it up and goes right to 13.

If it was just the voltage dipping at idle I wouldn't be too concerned but with the AC been so damn cold right now I'm curious if the 100amp Alternator really made that much of a difference (I'm not sure what amperage alternator it had in before), or if perhaps my issue is the voltage regulator?

Any ideas.

Apr 3, 2019 | 09:19 AM

henrikse

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Voltage regulator is built in to alternator but it could be bad. Not much quality control there days. AC should load the engine so maybe your bearings are causing engine slowdown in ac? Did ac work before? most cars have 68 amp alternator so there must be something else going on. The voltage to the ac should be minimal as it only operates the clutch. Also problem there perghaps

Apr 3, 2019 | 10:20 AM

haze324

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A/C used to work pretty good but not near as cold. I have to double check but I'm not certain if the new alternator has the same size pulley. Not sure if that would cause an issue?

Apr 3, 2019 | 11:05 AM

L-46man

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A 100 amp alternator is rated at 100 amp at 4000-4500 RPM. It's not doing anything near that at idle.
Your alternator should be putting out 14.3 + - volts.....not seeing anything good out of this alternator.

CHECK GROUNDS and bat terms. Check Voltage output.

sounds weak!

Unkahal

Apr 3, 2019 | 11:07 AM

henrikse

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From: Kelowna British Columbia

Quote:

Originally Posted by haze324

A/C used to work pretty good but not near as cold. I have to double check but I'm not certain if the new alternator has the same size pulley. Not sure if that would cause an issue?

is it factory air? If ac is turned off is all ok? 13.7 o so is normal output from alternator and 12 or so from battery with car off?

Apr 3, 2019 | 11:13 AM

haze324

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Quote:

Originally Posted by henrikse

is it factory air? If ac is turned off is all ok? 13.7 o so is normal output from alternator and 12 or so from battery with car off?

Air has been updated to R134.

If AC is turned off at idle in a red light my dash gauge is sitting at 13v (I need to check it with a digital meter to get an exact ready, but looks ok), and yes 12.7 at the battery with the car off.

Could it be the idle stop solenoid took a crap and with the AC on I need to bump up my RPM's a bit?

Apr 3, 2019 | 11:50 AM

mikem350

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From: Sunrise FL

First, dont depend on the dash gauge for accuracy. Use a DVM across the battery.

Running with ac on, in neutral, look for at least 13.8v.
If the battery stays around 12.7 key off, all sounds OK.

Apr 22, 2019 | 01:24 PM

haze324

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Quote:

Originally Posted by mikem350

First, dont depend on the dash gauge for accuracy. Use a DVM across the battery.

Running with ac on, in neutral, look for at least 13.8v.
If the battery stays around 12.7 key off, all sounds OK.

Mike all checks out expect when I put the car in drive. In neutral or park, with the car running I'm at 13.8 measuring with a DMM. I was not able to check it when in drive but it's a noticeable drop in power, the AC gets lower, and RPM's drop (from eyeballing the tach) from 750 to 700ish. If I pull up to a red light and put the car in neutral my dash volt gauge hovers over 13 and the ac remains strong. As soon as I put in gear everything reduces. Not sure how to adjust (or if that's the fix) my idle RPM's with AC on AND in gear?