2001 Tahoe..Only 6 volts at battery - No power - No start

[kirkh34]

Hello Everyone,
I have a 2001 Tahoe that I bought off my brother about a year ago. He used to have issues with it starting and he said he had to "wiggle cables" to get it to start. I have been driving it a year with no problem and then lost all power on the road and would not start. I tested ground at the alternator and saw 3 volts so I inspected the negative battery cable. I bought a new bolt for a better connection. There is very weak power with the key in and it completely shuts off when you turn the key. The battery has about 9.5 without cables connected but as soon as I hook up the cables it jumps around 6 volts. When I have the key to ON it jumps around 3 volts. I have checked all the grounds and they seem fine. I tried to bypass them all straight to the frame anyway with no luck. I also have checked all fuses and they are good. I'm unsure of where to go next as far as diagnosing this electrical problem. If anyone can point me in the right direction how to find out whats drawing power from the battery... I would greatly appreciate this! Thanks so much.

 

[Tonyrodz]

Possible your positive cable is corroded inside the insulation. You in a salty state?

 

[Fless]

First off, get that battery disconnected and on a good charger, then have it tested.

As @Tonyrodz pointed out, the battery cables tend to rot from the inside out. I'm not saying that's what it is, but it's definitely something to check based on your brother's history with it.

And welcome to TYF!

 

[kirkh34]

Thank you for the responses! I live in Indiana. Is there a way to test the positive battery cable without replacing it to see? I did take the battery into autozone and had it charged and tested and they said it was good. It is just low currently because of working on it and testing.

 

[drakon543]

ohm reading with a multimeter from end to end. also slowly move and twist the cable as you watch the multimeter reading. ohm reading should be minimal and shouldn't bounce around much while you move the cable around.

 

[kirkh34]

I got the battery charged. It will not start...only click. I took the starter off and tested it with the power connected. I grounded the case to the frame and turned the key and the starter worked. When I put it back on and try it just clicks really fast. It seems that there isn't sufficient ground from the block. I tested voltage across the ground and it's showing 0.7 volts. I tried to use jumper cables to bypass the cables just in case they were bad but still the same thing with the starter and same voltage. I'm not sure if this is a bad ground or something else?

 

[drakon543]

could be a poor chassis engine ground somewhere. if it was the main ground/negative you would probably have more problems than just a failure to start. also jumper cables generally wont allow enough instantaneous current draw to kick a starter. there are some pretty hefty and expensive jumper cables that can do it but generally speaking most readily available cables wont cut it. they are mainly meant to recharge and give an extra boost to a weak battery to allow a vehicle to start not power the vehicle completely. anyway i suggest checking your engine to chassis grounds as the starter is grounded through the engine. the other wires are obviously main starter power and solenoid trigger.

 

[1BADI5]

Well a starter working with no load on it isn't much of a test. The starter could be weak.

Think of pushing a car in neutral and then pushing it in first gear....... no load vs. load

 

[ks03]

.7v while cranking? Not just .7v or .7v key on?
I think rule of thumb for ground side is .2v or less
If the jumper cables didn’t help, my first thought is to try wiggling them around to try to get a better bite. Similar to using them when jump starting another vehicle, you could have had them connected but not well enough to support a high amp load

 

[OR VietVet]

Replace the battery and be done with it and then check for voltage drop problems with the negative and positive cables and just replace them as well with the age on them. You said your brother had problems and do you know the age of the battery? I bet you don't?