Its this because of the weather being cold, or is it the alternator?

When I am at an idle and give my 92 some gas the instrument cluster
and the headlights get noticeably brighter.

When going down the road all is fine and the gauge reads right in the middle.
Also, it starts up just fine.

 

If that's the factory alternator, that's somewhat "normal". The voltmeter reading indicates the charging system is just keeping up (barely) with the electrical demands of the car. Cold does have some effect, but how much I wouldn't know. Probably a good idea to eventually upgrade to a higher output alternator in the future. Both my 5.0's with the stock alternator would stumble and the instrument/headlights would dim noticeably if idling at a long stoplight at night - especially if running A/C / vent fan and a upgraded sound system. And "cold" around here would be low 70's at night.

 

I think it is the stock alternator. I will check into maybe getting a better one.
I just wanted to make sure that the alternator is the problem before I go that route.

 

Cold tonight in central Florida is 18 degrees!!!!
Yup 18 and it snowed here this morning!!

 

Thats it?? j/k In Nevada it is lower than that at night and just a couple weeks ago they were in the negatives at night.

Anyways back to your problem. If you have an Autozone they might check your charging system to see what the alternator is putting out and that will tell you if it is going out or if it is good. How much extra electronics do you have in the car??

 

I do not have any extra electronics. I even have the stock radio LOL

 

If you dont have any extras then I can prolly garrantee that it is the stock size alternator. It might be just starting to go out so like I said I would just take it to an Autozone to check it for you. I know th eones in my town do it for free so I am thinking that it should be the same there.

 

Ok, thank for your help everyone

 

No problem.


Now if you get it checked out and it is good then we can help figure out what might be doing that.

 

Ok cool. Thanks

 

Yep, doesn't hurt to test the battery and alternator output. When I did the 130amp alternator upgrade on both cars, ended up replacing the battery anyway...

 

I noticed when starting my 92 it was taking longer for it to start.
The battery is 3 years old so I decided to get a new battery.

I bought a Red Top Altima 34-78
Starts up great
It does not seem to be doing the issue with the lights getting
brighter at higher RPM thing.

I will see how it goes.

Thanks again everyone

 

Thats good to hear!! I just remembered to that if the battery is going bad the alternator wont put out the proper amount of amps either. To me it looks like the problem got fixed when you replaced the battery.

 

Glad it worked out.

 

All 3 of my 80's Mustang's/Capri's I've owned acted the same way, one even after replacing with a new alternator. I've always considered that normal operation for an 80's Mustang. They didn't dim a whole lot, but it was noticeable.