my headlights,parkinglights,dashlights,all have this @ idle. they have had this problem when i bought the truck(93 d150 5.2) 2 years ago.
i have changed the battery,battery terms,battery cables,alternator,belt tensioner,and belt. the problem is still there. i beleive the voltage regulator is in the computer. i even changed all the body and engine grounds that i could find.
could it be the alt?? the rectifiers or something in the alt??
i have a digital meter,but i may need to get an analog meter,some people say these are better for testing voltage fluctuation.
i thought maybe light switch bad,but i hooked up a set of driving lights on their own circut,and they also do the brite/dim,flutter thing.
any suggestions for testing this?? thank you

 

The regulator is in the computer. We need actual voltages in order to diagnose the problem since we can't see what is happening. What is the voltage at the battery and at the alt large terminal when the problem is happening? If they are pretty close and stabile the problem is not in the charging system and I would move on to the lights electrical delivery side.

I use a digital meter for most things and seem to get the results I need. Sometimes a test light is a better tool and it may be in this case because you can see the flicker. Use a test light at the battery to see if there is flicker there. If there is flickering there the problem is in the charging system if no flicker there move down the distribution wires until the flicker shows in the test light.

The technique I always use on electrical problems is to start testing in the middle of the circuit. This will eliminate half of the system that you have to test and send you to the half where to problem exists. On complicated systems I will move to half way testing in the problem half of the system. Continue this until the problem is found.

 

thanks seal,i will check some things out sunday if time allows.
i know the volts are good at the battery,and at the alt. when running,no fluct. when running. thank you

 

my mistake its putting out 15 volts at the battery with it at idle,took it to oreilly auto parts to have it checked,they gave me a new alt to try,but they seem to think its the regulator. i guess that would mean a new computer is needed??
they said the voltage is to high. the only reason i took it there is because all the parts are theirs and are lifetime.
should i order a new computer?? or is there another way to fix this problem. thank you

 

well i put on the other alt that the part store gave me to try. same thing 15 volts @ idle at battery. if i take it up to about 1500 rpm it puts out 15.3 @ the bat. i ordered a new computer,it will be in tomarrow morn about 10:30.
i love dodge trucks,had many but this one is a dam money pit.i have so much into it i will have to keep it forever. eventually it will all be good.
no wonder my old battery had dead cells in it,(overcharging) it was only 2 1/2 yrs. old. thank you

 

WOW that was quick. I would not have changed the computer myself due to a regulator problem. I would have put a regulator in it for a lot less money. You know this is a common problem when the after market has come up with a fix.

http://www.alternatorparts.com/exter...nator-kit.html

 

checked all the wiring,and field wires,all looked good.
i put the new computer(ecu/pcm) in it is more responsive and runs even better(ran good before) but still puts out about 15.2 @ idle @ the alt and the battery.
maybe that is just the way this truck is supposed to be.
the ecu that was in it was an aftermarket not original also. thank you

 

Have you checked with another meter?

 

yes auto part stores meter and mine.

 

could a faulty ignition switch cause this??
it starts fine,but could 1 part of the switch be bad?? its probably the original from 93. thank you