Dash lights randomly flickering

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BravoDrew
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Dash lights randomly flickering

Postby BravoDrew » Tue Feb 14, 2017 5:30 pm

Today for the second day I noticed the Volts, Filter and Brake light randomly flickering, accompanied by a loud clicking sound, flickering on and off at random times while driving my 86 turbo pup. It seemed especially bad at a stop light, then seemed to pretty much go away. The other day it happened while I was parking after a long ride. Anyone experienced with this?
New owner, '86 Isuzu P'Up Turbo Diesel SpaceCab, 5-spd, 2wd, Long Bed

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puttputtinpup
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Re: Dash lights randomly flickering

Postby puttputtinpup » Tue Feb 14, 2017 7:06 pm

My 1st guess would be to tighten up the alternator belt, and check your ground connections real good. That's all I have to offer you right now
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mja
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Re: Dash lights randomly flickering

Postby mja » Fri Feb 17, 2017 4:28 pm

When the lights are flickering, see if your blower motor is intermittent. If that's the case, it's probably the charge/blower motor relays (electrical switches) clicking.

A couple things - the voltage regulator which is internal to the alternator controls this whole circuit. Proper alternator charging controls the voltage regulator. So check the alternator first, if that tests out, check that the connections to the voltage regulator are solid/good. The regulator is expensive and difficult to replace - need to drop it off at an alternator shop to have it installed properly unless you're good with electronics.

It could also be the relays themselves, although the likelihood of 2-3+ independent relays flickering/failing at once is pretty close to zero. If the alternator is good, you can jump/bypass the stock voltage regulator, check out my last post in another thread on that topic. Edit - I should say this is a temporary fix with stock alt... it wouldn't be smart to run an alternator without any type of voltage spike prevention, could blow out fuses/burn wires.

One last thought - it could be the wiring too, if it's chewed up or has a short. You never know.

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JoeIsuzu
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Re: Dash lights randomly flickering

Postby JoeIsuzu » Fri Feb 17, 2017 5:52 pm

puttputtinpup wrote:My 1st guess would be to tighten up the alternator belt, and check your ground connections real good. That's all I have to offer you right now

mja wrote:When the lights are flickering, see if your blower motor is intermittent. If that's the case, it's probably the charge/blower motor relays (electrical switches) clicking.

A couple things - the voltage regulator which is internal to the alternator controls this whole circuit. Proper alternator charging controls the voltage regulator. So check the alternator first, if that tests out, check that the connections to the voltage regulator are solid/good. The regulator is expensive and difficult to replace - need to drop it off at an alternator shop to have it installed properly unless you're good with electronics.

It could also be the relays themselves, although the likelihood of 2-3+ independent relays flickering/failing at once is pretty close to zero. If the alternator is good, you can jump/bypass the stock voltage regulator, check out my last post in another thread on that topic. Edit - I should say this is a temporary fix with stock alt... it wouldn't be smart to run an alternator without any type of voltage spike prevention, could blow out fuses/burn wires.

One last thought - it could be the wiring too, if it's chewed up or has a short. You never know.

I'd replace the alternator brushes before taking it to a shop. They're pretty cheap, and can be easily replaced without even removing the alternator. And with a lot of miles on them, they do wear down. Relays are indeed a possibility. A bad "charge warning relay" could cause the symptoms you're seeing (without any others being bad).

Jack


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