I have an electrical problem on a 93 C-1500 2wd 5.7lL engine. It has moderate mileage. I'm loosing amps plus I'm loosing my mind trying to solve this.

One evening, without warning, the lights dimmed, radio cut off and heater blower motor stopped. The truck was barely running and hesitating but did not stall. The stock dash amp meter showed an increased draw or discharge as I accelerated. The needle pegged backward at 9 amps as I drove home

I knew the battery was already marginal and I inspected the serpentine belt and alternator. The small threaded + contact was loose on the back from inside the alternator; this is bad. So off to the local autoz chain center I went. I purchased a new battery, belt and alternator (105 amps like stock).

Replacing these items did not fix the problem. I have 14.1 V at the alternator and at the battery when the truck is at idle. Increasing to 3000 rpm increased the voltage to around 14.3. I did voltage drop test across the alternator connections and each of the fusible links I could locate under the hood. No voltage drops were found. I took the truck back to the local chain store who load tested the system on the truck. Their tests showed no failures and a normal reading. I had them test it twice over three days.

I have pulled the starter and solenoid and tested with a loaner. No dice. I swapped the alternator for a loaner too; no luck. I have removed the stereo's amp. No other add on equipment is installed. I have removed the ground cable from the engine block and cleaned it. I have cleaned the battery cables at all ends. I have checked wire connections where I see connectors and replaced those connectors. No joy. I don't have access to a true amp meter but starting the truck with all electrical off shows at 14 on the dash. As soon as you place your foot on the break, the amps drop to just above 9. Turn on the heater or stereo or place it in drive and it will peg down to 9 amps or less according to the gauge. The electrical components then begin to compete for power causing what seems like a starvation of power.

I can sputter it up to highway speed and the amp meter does not indicate a charge. It discharges. Once, I thought I saw it jump to 14 which may indicate a poor connection. It seems like I have excessive resistance somewhere or a component drawing excess power, perhaps continuing to run when it shouldn't. I don't know and neither does any one who has looked at the truck.

Please help me figure out where to look next. I'm stumped. Thank you

 

well it look's like you have done every thing,they only thing i can say is i had a brand new rebuilt alt from o'reiley's and it went crap's would work then not !i made them take it back and give me a new one ,it would work for them every time ,put the other one out in the lot at the store (had it down to sience)and tools handy .all i can say check all your body ground's expecially tail luight's ,body to frame ,rad support to frame every thing ! if you dont have a good ground you dont have any thing .add some if you think,it wont hurt .

 

It sounds like you have a bad ground somewhere, somewhere in the dash or with the electronics, not the motor ground. Its like this one issue a coworker told me he fixed for a lady: She complained all the appliances in her house would randomly come on and off and would "compete" for power. What was happening was they were actually competing for a path to ground, the ground at the incoming servicehad come loose in the meter and caused her house to flicker randomly as the lost appliances and lights were searching for a ground. So yea, i'd about bet it is a poor ground somewhere inside the cab. Could it possibly be the computer ground? Pull you glove box liner out and check the computers ground.