flickering headlights

[MattHarrell]

My ''91 has recently developed a problem where the battery gauge and
headlights seem to pulse up and down. I've got a new battery in it and the
battery cable is only about a year old. I'm about to go in there and try to find
the ground strap and possibly check on the regulator. AutoZone tested my
alternator and they claim it's fine. Is there anything else I should check
into? The truck has recently developed an occasional hard start (seems
like a low idle?) on the first try but it will always start up on the second - not
sure if this is related but it's one of the reasons I'm checking the ground
strap.

Also, I have hooked a gauge up to the battery and it seems to hang out
in the normal realm according to the manual - I think the dash gauge is
hyper-sensitive but this doesn't explain the headlights flickering when
nothing else is happening.

 

[mdrut]

Welcome to the site, The ground is the problem in 75% of electrical problems, once you have determined that it is not the problem, have the starter checked..Sounds like you have a dead short someplace, due to the high current draw, it has to be in one of the motors: starter, fuel pump, wipers, windows, seats,....Also, the regulator could be sticking...If it was "open" when they checked the alt., the problem might not show up...Good Luck..

 

[jimbo74]

flikering or dimming flickering is on off on off dimming is just less light. i to think you have a voltage regulator problem as it is fairly common. my car does it too. if you use a high draw device... my battery is an optima y-top....so i know it isnt the battery.....it could be just running to many accessories and the stock system cant keep up...... when the bass hits in my stereo the face plate dims.....

 

[tac0meat]

most "vintage" explorers(navajo) have similar problems. i think its because the pulley on the altenator is too large so it doesnt spin fast enough to put out enough power at idle. i know its not a problem with the battery or altenator on mine(optima red top/200amp alt.) and mine still does similar things. even with all that i also get some dimming when my bass hits at idle

 

[MattHarrell]

Oops, sorry. I didn't mean flickering in that sense - I meant dimming. They don't actually go off. I also can't easily tell if it does it while I'm
driving - I haven't noticed it. This dimming happens even when I don't have any other unusual loads - stereo off, engine on, lights on, AC off.

The battery is new - it's an Optima red top I had in my garage that I was going to put in the car but this seemed more a priority.

Sorry, haven't had a chance to test anything yet - I would do it now but it's 95 degrees out there and I don't think too well in that kind of heat.

If the ground and regulator check out Mdrut mentioned it could be the starter. I have been also noticing it's "hard" to start when the engine has fully cooled down. Hard's in quotes because it doesn't catch the first time but when I turn it off and then try it again it fires up fine the second time. Run's great once it's going.

Anyway, I'll check these things out and get back to everyone. Other than visually, is there a recommended way of testing the ground straps? If I can find a way to reach it then I was planning on using my multimeter to check the resistence but I'm not sure what the expected value would be (other than low).

 

[JDraper]

Your resistance on the ground straps should be in the ohms range at most. If you get into the kohms range, you've got a problem. Test from your your battery negative terminal to the frame, the battery negative to the motor, and the motor to the frame. On my truck, the resistance values are all under 5 ohms. Just make sure you get good contact.

 

[MattHarrell]

Okay, will do. The engine was just put through an hour long drive back from the mountains so it needs a little time to cool before I go poking around on it. I should be able to do this in a little while.

Battery negative to elsewhere - is that with the battery negative cable attached or off?