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Low voltage - what else can I check?

With electrical, always start at the source and go from there to the end of the circuit. Verify batteries are good. Then connections, rusty or corroded - fix it. Maybe that is the problem. Before it was vetting 90%, then a year later 80%, now it could be at 1% too low to work.

It is easy to start naming parts to throw at it and hope something fixes it. But that can be a lot of $, time, and sometimes you add problems due to new defective parts.

I have seen rigs sold because of a bad electrical connection. I once bought a 65 stingray because the place that rebuilt the engine and installed a new trans for the guy forgot to tighten the distributor hold down bolt. The owner flipped out, I stopped him from destoying the car, he was trying to syphon fuel to pour on it and light it on fire. 10 minutes work and I made $5,000. When it resold (man i wish i could have that car now). Take your time and do it right, or youll be redoing it later.
 
I'm thinking its a loose wire. Going down the road the door in the dash that clicks when you turn switch on kept clicking over and over. Then got on shoulder of the road were the wake up bumps are the speed,etc goes crazy. And trying to shut off.
 
Thats exaclty what it sounds like to me. Start disconnecting and cleaning anything suspect.

You can also have the truck running and give the harness a shake trying to find it. What year is your truck- is it ds4 or db? Loose wires or bad grounds give pmd and ecm nightmares
 
Checked all wires wiggled harness. Battery cables good, Grounds are good. Checked voltage at alt. 14 v check battery volts 14v. voltage goes back to 14 at times until lights or fan blower is on. turn both on volts drop to low starts trying to cut off. tryed taking for spin again. same ole thing. Brake light is also on.
 
Ok played with the wires and all again today. Somehow the voltage is holding and truck isn't cutting off. Alternator is whining high pitched noise. It gets hot to touch quick. The big wire off of it is hot though.
 
Sounds like you have a big draw on the alternator. Maybe a short or relay stuck. Try pulling fuses and see if anything changes. Wire should not be getting hot.
 
I guess I didn't ever really resolve this. The Suburban has around 260,000 on the clock, now and it still gets driven fairly regularly. I'll be back on it soon, though, I hope, because it is looking like it's going to be my winter snow vehicle and will be sitting in the barn, instead of a cozy garage. It cranks hard when it's below zero.

I drained out the 15W40 oil and put in 5W30, so I hope that makes a difference when it's cold. I'm still planning on going over wiring, though.
 
70 Oldsman said:
Just a heads up. I went got a new alternator,the old one squeal and getting hot. Old one was under warranty so no loss of $$ just time,labor,gas.
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Did you reuse the old pulley? The ones for gas engines are a different diameter, the tach will read wrong as it gets it's signal from the alt.
 
ak diesel driver said:
Sounds like you have a big draw on the alternator. Maybe a short or relay stuck. Try pulling fuses and see if anything changes. Wire should not be getting hot.
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Like he said- stuck relay or short.- first check for a short, then swap relay with a good one if no short is found. What amperage is the pump drawing compared to spec?
 
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