Electrical gremlins part 36

[MikeO]

Symptoms for the last year.



Tough to start.

Low voltage after startup - somewhere in the 8V range.

Wait to Start light starts to flash somewhere around 30 minutes after startup... flashing slows... eventually it goes off and the truck goes right back to normal 14V operating voltage.



So far, I've:

Replaced the ground cable and negative to body ground (that solved a lazy/slow turn signal issue I've had for years). I wasn't getting a good ground between either the body or engine and negative terminal before.

Replaced both relays for the grid heater.

Unplugged every fuse and relay during the low voltage window... nothing fixes it.



The only other two things I can think of are the alternator/regulator or the ECM (if that's what it's called) on the inner fender well next to the battery.



The one thing that is odd is that the relays are not being told to send voltage to the grid heater even on a 35 degree morning.



Any thoughts would be greatly appreciated.



Mike O.

 

[PToombs]

Does it work normal if it's warm out?

 

[JAG1]

I think what you got is a combination of two things.

First, I think you have bad starter contacts, that will draw the battery down very fast. On my first gen, it really was the ring that contacts the starter contacts that was corroded. It ran down the batt to nothing after trying to start.

Second, I think you need to clean and retighten all grounds and poistive wire contacts. Especially the main charge one on the back of the alternator. I use a fine grain sandpaper to clean the terminals and connectors.

The alternator has a ground wire too... . its very important that you find this wire and clean it as well.

P. S. don't let my sig fool you, I have a first gen w/ 300+k miles on 'er

 

[MikeO]

No, it does this whether hot or cold. It could be 90 degrees out and it still does this.

I am leaning towards a bad PCM right now because that controls the grid heater and is the voltage regulator.

I am going to check all the grounds just to be safe though.

Mike O.