Headlight problem

DJPORTER

MEMBER
1993 GEO PRIZM
193,000 MILES

I have a 1993 Geo prizm lsi 1.6l with an electrical problem. When cold, everything is fine, after car warms up, voltage drops and headlights dim. It has a new battery and alternator tested fine, albeit in cold state. Terminals are clean and no loose connections. What I find odd is when the problem presents itself, the voltage will drop to about 11.5 and stay there. Any ideas? Is it alternator failing or do I need to look elsewhere?

4 Replies

CADIEMAN

MECHANIC
3,544 POSTS

Replace the alternator 11.5 is way to low.

Was this

answer

helpful?

Yes

No

Tuesday, December 20th, 2011 AT 2:16 AM

KHLOW2008

MECHANIC
41,814 POSTS

Check the crank pulley if equipped with harmonic balancer. Ensure the alternator belt is adjusted correctly.

SPONSORED LINKS

Was this

answer

helpful?

Yes

No

Tuesday, December 20th, 2011 AT 4:11 PM

DJPORTER

MEMBER
1 POST

Interesting, problem surfaced after I had replaced the harmonic balancer. It was a used part pulled off a car. What should I check for as far as that is concerened? As far as alternator belt, it doesn't seem loose. Can it being too tight cause a problem?

Was this

answer

helpful?

Yes

No

Wednesday, December 21st, 2011 AT 2:55 AM

KHLOW2008

MECHANIC
41,814 POSTS

Tight would not cause the problem described but it might emit a humming noise.

The outer ring of the crank pulley could be freewheeling over the inner pulley if the harmonic balancer is bad.

Use liquid paper to draw a line across the face of the crank pulley. Run the engine and after a few minutes, stop engine and if the line is out of alignment, the harmonic balencer is bad causing the non charging.

Was this

answer

helpful?

Yes

No

Wednesday, December 21st, 2011 AT 2:12 PM