Low voltage

Bigsky_Boarder · Jul 21, 2018

Started my truck the other day and my voltage is in the red zone, speedometer and tach move with the blinkers, windows take forever to roll up ect. The battery is fairly new, what are the other basic things I should check that would cause this?

kennythewelder · Jul 21, 2018

Sounds like the alternator is not working. Start the truck, remove the positive battery cable. If the truck dies ( engine quits running) then the alt is not working.

magimerlin · Jul 21, 2018

The basics.... check the battery, check the alternator, check your ground. And NO, before you think to ask or try it.... taking the cable off the battery whilst running to check the alternator is NOT a proper and or good test to see if your alternater is working. By doing so could actually hurt the computer. That goes for ANY vehicle that has an ecm.

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magimerlin · Jul 21, 2018

kennythewelder said:
Sounds like the alternator is not working. Start the truck, remove the positive battery cable. If the truck dies ( engine quits running) then the alt is not working.

No do NOT do that.... it can hurt the ecm(trucks computer).. that is not a valid test on ANY vehicle with an actual computer in it. That is the old test for carburated vehicles only as they are not computer controlled and not affected much, if at all, by any voltage spikes.

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magimerlin · Jul 21, 2018

You can get it tested at most any auto parts store. For free...

Can test it with a voltmeter as well. With all still hooked up. Start it and test the reading with a multi meter. At the back of the alternater and at the battery. Should be showing roughly 14.4ish.

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mistaake · Jul 21, 2018

kennythewelder said:
Sounds like the alternator is not working. Start the truck, remove the positive battery cable. If the truck dies ( engine quits running) then the alt is not working.

did you just seriously suggest that? NEVER do that on any computer-controlled vehicle.

Bigsky_Boarder · Jul 21, 2018

Thanks for the info, i figured I'd ask in case it wasnt the battery (and I'm stupid when it comes to electronics lol)

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evilunclegrimace · Jul 21, 2018

magimerlin said:
No do NOT do that.... it can hurt the ecm(trucks computer).. that is not a valid test on ANY vehicle with an actual computer in it. That is the old test for carburated vehicles only as they are not computer controlled and not affected much, if at all, by any voltage spikes.

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mistaake said:
did you just seriously suggest that? NEVER do that on any computer-controlled vehicle.

This^ PLUS it also applies to ANY vehicle with an Electronic voltage regulator regardless if it has an ECM/Computer

east302 · Jul 21, 2018

magimerlin said:
No do NOT do that.... it can hurt the ecm(trucks computer).. that is not a valid test on ANY vehicle with an actual computer in it. That is the old test for carburated vehicles only as they are not computer controlled and not affected much, if at all, by any voltage spikes.

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I’d heard of that as a “test” as well but never tried it. Thanks for posting the heads up.

kennythewelder · Jul 21, 2018

mistaake said:
did you just seriously suggest that? NEVER do that on any computer-controlled vehicle.

Ive done that for years. Never had an issue. I would not do it on any thing with a BCM, but on these old OBD 1, and OBD 2 systems, chances of messing something up are slim to none. Not saying it cant happen, just saying chances are it wont.

Low voltage

Bigsky_Boarder

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kennythewelder

Officially Retired, B31-3 (6-G) certified welder.

magimerlin

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magimerlin

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magimerlin

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mistaake

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Bigsky_Boarder

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evilunclegrimace

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east302

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kennythewelder

Officially Retired, B31-3 (6-G) certified welder.

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