Heat and charging

[70mustang63b]

I searched around, but didn't really find anything too close to my problem in the forums. Car is a '95 GT. When the outside air temp is warm (85 or so and hotter) my gauge on the dash (stock gauge) shows a drop in alternator output. At a stop light the gauge goes to about the low side of the 'O' in NORMAL, and if i step into the car too hard it'll bog just a bit, but not die. This happens only when it is hot outside. The car in cooler temps always runs with the needle right in the middle of the normal range, but when the outside temp goes hot, the charge drops. Problem is being able to test this problem as it only occurs when it is hot outside, and by the time i got the alt to a shop to bench test it is would be cooled off. Anybody experience this and might have a clue what to do? I hate to replace the alt if it isn't the problem.

 

[99FiveOh]

Maybe because when it's hot outside the fan is running on high speed most of the time. When my high speed comes on I can see a descent drop in voltage. Usually when I'm at traffic lights. When I go to take off it goes back up.

Do you have underdrive pullies by chance?

 

[70mustang63b]

Nope, no UDs on the car. Maybe it is the fan, but then something must be wrong somewhere. If it is then Ford made a car that would stumble a bit in hot weather...that isn't right.

 

[HISSIN50]

Gary, if it is fan related (you only have the issue when the cooling fan [and often HVAC fan] are on), it's not uncommon from what I have seen. I have a similar issue on my 94. The car idles a bit lower with the additional load of the AC compressor and relatively large electrical draw of the fan(s), esp at night. We cant see the exact issue you're having - you might be rolling your eyes at me. I'm just not seeing what you do.

One thing to double check is the IAC - make sure it's clean and functioning (it helps compensate for the load of AC).

Otherwise I would simply band-aid by running the idle up a hair (I choose to use the throttle stop, while some prefer to use the air-bleed on the IAC).

These cars saw extensive high-desert testing but they are all now 12 years old or so and have some miles - they like to bicker at us a little bit.

Oh, Brian is sending me a controller - I'm eager to see how it helps the system-load compared to the big 'all or nothing' draw with our stock relay-driven fan speeds.

My two cents. Good luck.

 

[70mustang63b]

I may look into the idle thing and raising it a hair.
The only thing is that this prob doesn't always occur with the HVAC system on, it'll happen even with all the HVAC off. I have even seen it happen at night with the lights on, so maybe the alt can't deal with heat and a load on it.

 

[99FiveOh]

It's not the heat on the alt. It's the heat that's causing the fan to opperate, thereby lowering your volts. If you are unsure about your alternator, then have it tested, this will tell you what's going on.