electrical idiot needs help

[bnc04]

Need some electrical diagnosing help

My 88 350 tbi has started doing some strange and inconsistent things.

Voltage drops intermittently- caused by several things like, Running Blower fan, When brakes are hit, When turn signal is activated. When power windows are used. When the radio is on, it will cut out when this happens. It happens when every accessory is off. Radio, Amp, Fan motor, etc . The problem is not constant and at times there is no issue at all. Sometimes while driving, the volts will drop, then recover. Sometimes, They can be raised up again by activating the windows or turn signal or brakes. Sometimes when I try and start the truck, the acc will work ( lights, buzzer etc) in the first position but there is no starting the thing, It is just like a dead battery. If I try it a few times it will eventually “ catch” and fire up.

What I have done.

Replaced break light activation switch.
Cleaned Taillights connection both cable and bulbs.
Run a ground from battery to Body


I’m pretty sure I have a bad ground somewhere but I can’t get a feel for where to look. I’ve done some looking around and can’t see anything obvious.

Do you guys have any suggestions on what to look for and how to look for it?

Isolation techniques?

Thanks in advance,

Brett

 

[ryoken]

grounding sounds plausible but since your having a "no power" issue at acc it could be a power supply issue down at the starter or a fusable link sh*tting the bed... remember, those connections at the starter take alot of corrosion abuse..

one thing people often overlook is the actual lug connections at wire ends.. "oh, its hooked up, its good" whenever suspect, i always give wires a good wiggle and tug.. invaluable for us diagnosing boat issues in such a corrosive enviroment...

 

[MarcS]

Some things to try/check.

Do you still have a ground to the engine block and not just to the body ?
Check the connections on the starter solenoid ?

The guage will bounce when you use your windows and other accessories but should recover. Sometimes connections come loose, especially on gauges, verify the voltage is dropping with a multimeter. Use the cigarette lighter so you can watch the guage and the meter. Tap on the meter to see if it recovers also. If it does, its probally a loose connection or the meter itself.

 

[jaros44]

Electrical Snafu

I suspect grounds as well, I don't have your yr. truck but a factory wiring diagram may lead you in the right direction. How about your ignition switch it self, it's only been turned on and off 18 gazillion times in it's life, and it is a switch??? Just my $.02 Later J.

 

[opfor2]

I have the same kind of problem on my 90 Blazer. I'll be sitting at a light and all of a sudden the volt gage will be reading less than 13 volts then as soon as I start driving it will recover. I have dual Optima batteries one red top (starting) and one yellow top aux batteries, all of the grounds that I can find have been removed, cleaned and then reattached. The only ground that I couldn't remove is the rear engine block to body ground, cant reach the bolt behind the dizzy. BTW both batteries have both batt to frame and batt to body grounds. This problem occurred before I replaced the alternator with the new 200 amp one so I know it's not the alt.

 

[mouse]

I have the same kind of problem on my 90 Blazer. I'll be sitting at a light and all of a sudden the volt gage will be reading less than 13 volts then as soon as I start driving it will recover. I have dual Optima batteries one red top (starting) and one yellow top aux batteries, all of the grounds that I can find have been removed, cleaned and then reattached. The only ground that I couldn't remove is the rear engine block to body ground, cant reach the bolt behind the dizzy. BTW both batteries have both batt to frame and batt to body grounds. This problem occurred before I replaced the alternator with the new 200 amp one so I know it's not the alt.

Sounds like a weak alternator.