This evening we drove our 1976 Cutlass Salon to a local car club picnic. On the way home, we noticed that the headlights were very dim. All of the other lights seemed to be working properly and the air conditioning was operating as it should.

Upon arrival home, I compared the lighting situation to our Jeep to confirm that indeed it was only the headlights which were affected. Sure enough, the Jeep's other lights were comparable but the Olds's headlights on high beam were no brighter than the Jeep's low beams. With only the parking lights on, I turned on the Salon's high beam headlights and noted that its other lights dimmed only the tiny amount which one would expect.

I ran some basic battery voltage tests and here is what I found:

12.5 V at the battery, engine running with high beams on.

13.8 V at the battery, engine running with no load (lights off).

13.0 V at the battery, engine off with no load.

This confirms what I suspected: the charging system is not the problem. Granted that the battery's static voltage is a tiny bit low . . . but not that low!

What could cause such a drain on only the headlight circuit? Could the dimmer switch be bad? It is the optional column-mounted switch (if that makes a difference). The headlights do seem to switch from low to high beam rather "slowly" once the lever is depressed.

We have owned the Olds for thirteen years and have never experienced these problems before. This is a well-maintained but infrequently used car with a fairly recent battery. We want to use it again on Saturday but I am afraid of getting caught out past dark with this problem. Suggestions . . ?

Jeff Dreibus

 

Actually 12.5V at idle with the lights on is low. I would have the alternator tested. If that proves to be good then start looking at the wiring as the culprit. Check all of the connectors on the lights, battery, grounds.....everything and make sure all of the connections are solid and clean.