Alternator Woes

[gogmorgo]

Bad regulator? Something in your charging system is cooking things... Could be a short or bad connection somewhere else,

[Goose]

The shop has it now. They'll fix it, I'll just have to pay.

[Goose]

Going nucking futs. Alternator is working, battery charged, drive for about 2 hrs, truck dies. Battery is dead. Alternator is still putting out 14.7. What gives? If the alt is charging, shouldn't the truck run off the alt? Battery is an optima redtop, seems to charge fine. I always thought the battery was there for starting, and everything else ran off the Alternator.

[Bornindesert]

Could be a number of things, first place I'd look is terminals, grounds and connections at battery, alternater, block and starter. Beyond that, probably looking at trouble shooting from the tech manual? Assuming it's all stock wiring...

[Goose]

It's an 88 truck, but the motor/trans is out of a 93 Cherokee. The swap has been in there for a few years. In november I installed 4 offroad lights and a cb. Decided to upgrade to the optima. Everything was fine, then my alt. Went out end of January, I've had problems ever since.

[Bornindesert]

I know the feeling, my 88 MJ is a hybrid too, has a '91 motor and engine harness. If the alternator is putting out, that's a good sign. If the battery is not picking up the charge it should be fairly easy to find the bad connection, should see like 14v at the + terminal at idle. Might need to understand if the battery is discharging too when the motor is shut off. This stuff always happens when its either freezing cold or raining out...

[Goose]

The shop said after the motor warmed up and the alt was under load the voltage would drop to around 10v.

[Bornindesert]

That doesn't make sense to me, the 12v battery would discharge into the 10v source. The alternator should regulate to maintain the battery at 12v and supply any electrical loads like high beams. It's true that the alternator will cut back once the battery is fully charged.

[Goose]

I have a short somewhere. They replaced the alt, I picked it up. On the drive home, my dash lights and headlights were way brighter than they used to be. And under acceleration the radio and radio display shuts off. Hit the brakes, it comes back on.

 

Wtf?

[Bornindesert]

If there's a short somewhere, should see it as a resistance between the red positive terminal (with it removed from battery) and a ground point. If there is no short, the resistance is close to infinity, or very high. If there is a short, you should read some resistance on the Ohm meter. Once you get a fix on the resistance, try and remove fuses or disconnect connectors until it goes away. Then you've isolated the bad circuit. The brake could be the source of the intermittent ground, may need to pump it and watch the Ohm meter. Hope that helps.

[Goose]

Did a draw test, didn't find anything.