Hi Scotty,
Got a bit of a mystery in my 2007 Ford Escape, 2.3L inline 4, automatic trans, with around 278K miles. I think is the alternator that is giving out (original factory), but the signs are strange.
When driving or at highway speeds, and air conditioner on, the voltage readout is at mostly steady 13.4 - 14.01. But if I have to come to a stop, the voltage drops down to below 12.4 and bottoms at 12.1 - 12.3 ! If I am driving without the AC on, and I reach a stop, the voltage remains around 13.3-13.4... is my AC compressor shorting out or low in charge??? or alternator giving up ???
A thousand Thank you ! for your help Scotty,
All the way from sunny Miami, Florida,
Eddy
Is it just when the AC is on or whenever the blower motor is on? The blower is a heavy draw and a weak alternator will often not be able to keep up at idle, but when you are driving, the RPMs will be higher and it can keep up. Try turning all of your lights on (exterior and interior) and see if the voltage drops at idle. If it does, then you probably just have a weak/dying alternator.
The AC compressor is usually belt driven and has no affect on the battery voltage.
Thank you ! I must say that I can't recall noticing the voltage dropping that extremely significantly with all the lights on, as when the ac is running. I be inclined to say its not the blower motor, since turning off the ac ( turning the switch to the off on the console) which does not turn the blower motor off, and just giving a little pedal to the gas as to inch the car forward, brings to voltage up from the bottomed levels...
Load test the battery and alternator to find out about their health. If they check out, your AC compressor is on its way out.
Thank you Yaser for your help too.
Is there any test I can run to check if the AC compressor is ready to go kaput on me ??? I have a new AGM battery installed not long ago - less than 3 months, and using one of the testers Scotty has shown in his videos to check battery life and so, it shows battery with 100 life, and it doesn't give me a bad charging system either..
You should load test the alternator. Part stores do it as well. If you have a good alternator and battery, then the symptoms you have are due to the bad AC compressor.
I'll swing by the Autozone near the house and ask them to run a load test on the charging system. I had to replace the original compressor about +/- 10 years ago.. it quit on me at a trip back from Tampa, it just died. How can a bad AC compressor affect the voltage ?
It shouldn't have that much effect. It runs off of the 12 volt accessory unless it is directly connected to the battery itself, there should not be an excess voltage draw.