*Car Electrical Test*
Posted by: Californian
Subject:Darned auto electrical problems
Well, I've been posting about my 1968 Ford pick-up and it's electrical problems for about a month, now. To review, I'm having trouble with my high beams. When I have them on for between 6-8 minutes, they start to blink off and on. Low beams always work just fine. I've replaced the main headlight switch, the dimmer switch, all of the wiring from the dimmer to the bulbs in the high beam circuit, the alternator (went from a 32 amp to a 61 amp) and voltage regulator. It still blinks after 6-8 minutes. It's almost as if I have a circuit breaker going bad, but I can't find any breakers. Any ideas or suggestions? Does anybody know where I can get a wiring diagram for a truck that old? Chilton doesn't have diagrams in their books, and Haynes doesn't even have a book for trucks older than the mid 1970's. TIA
Californian
Resist or serve
Subject: Test for intermittent problem...
Posted by: Ronald H Levine
In reply to: Californian
Subject:Test for intermittent problem...
Make a small 12 volt test light with long wires and needles
soldered on instead of alligator clips.
The first thing I would suspect would be the headlight switch
because of the time delay corresponds to heating a thermal circuit breaker,
but you changed that already. There might be a relay to check. Even if the
components work, it might be the connector that pushes on has lost it's
squeeze on the terminals. Whatever it is, find it with the test light I
described with the following method. Pick one thing that you suspect or
choose to test first. Maybe test the new light switch. Stick one needle
through the wire going to the switch from the battery (comes from the
fuses). Stick the other needle through the wire going to the high beam of
the headlights. The needle pierces the wire insulation and goes between
strands of copper wire without breaking them and out the insulation. The
compression of the wire strands in the insulation that surrounds it makes
reliable electrical contact for your test light. If necessary, a wrap with
some light cardboard and a piece of tape prevents the needle from touching
other metal. Put the test light on your instrument panel where you will see
it when you drive. The problem you had is that it is an intermittent
problem. It is hard to be probing around when you are driving at night when
your lights are going off. With this simple test light that you hook up in
advance, all you need to do is to see the test lamp flash on every time
your high beams flicker off. If it does that, the problem lies between the
two needles. If the test lamp does not come on when your high beam lights
flicker off, then the problem is not there and next time test another
component till you find the one that causes the flicker. When you finish
and pull out the needles, the wire doesn't need any repair. It's insulation
suffers only two tiny needle holes and the copper inside can't make contact
with any metal. Then you are ready to test the next suspect component till
you find the problem. Another good thing to test is the high beam switch on
the floor where it gets exposure to water and mud over the years.
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