My 93 W350 5sp. has been giving me some electrical fits lately and I need some advice on what to try next. It started a few weeks ago when the ameter only showed about 9.5 volts charge and while driving would stay there for quite some time, then jump up to 14V and stay there for awhile. I also saw thisin the headlights (do most driving to and from work in the dark) as they dimmed dramatically when the charge dropped to 9.5V.

First, I took all the grounds and cleaned them thouroughly. This did nothing. Then I switched the #1 (charge) and #3 (A/C) relays on the left fender. This did help somewhat. Now the truck only charges to 9.5V when you start it and drive for 2-6 miles, then jumps around back and forth 5 or 6 times, then goes to 14V and is fine. If the truck is warmed up, it goes right to 14V no problem. I also have lately noticed the starter not energizing when I hit the key. I've got electrical power to it, but have to tap it a few times. Is this the same issue or different? Also in the last day or so the truck is not cranking over very fast, like the battery is low on juice.

Lastly, this all started happening about 4 weeks ago, when the serpentine belt broke while driving home from work. I had to limp the truck about 2 miles before I could pull over and stop. But it seemed to start and run ok after I installed the new belt for about a week, then my troubles started happening. Nay info where to start looking? Thanks for any ideas, in advance.

P.S. I put a new alternator on it about 5 months ago, and a new battery about the same time as well.


Thanks

Mike

 

Have you tryed replacing the batterys? Seems like that could be a problem.
I don't think your's has a intake heater,or I'd think thats what it was...my truck allways does that when its cold and its normal.

 

I'm not sure about your model year but the crank position sensor tells the computer that the engine is running and will energize the alternator, allow the A/C to work and send a signal to the tach gauge.

If you have A/C does it work when the voltmeter is around 9? And/or does the tach work when the voltmeter is around 9?

Again, sorry if I'm off base about the 93

 

I had the exact same problem on my '92 a few years ago, and it was the crank position sensor. You said the serpentine belt broke, well it probably hit the wires on the sensor on it's way by and caused some kind of damage that showed up later on... I changed the alternator and battery and scratched my head a lot before somebody on here tipped me off to what it could be... I got a new sensor at Napa for around $90 CDN. Hope this helps!

 

Quote:
Originally Posted by manureman
My 93 W350 5sp. has been giving me some electrical fits lately and I need some advice on what to try next. It started a few weeks ago when the ameter only showed about 9.5 volts charge and while driving would stay there for quite some time, then jump up to 14V and stay there for awhile. I also saw thisin the headlights (do most driving to and from work in the dark) as they dimmed dramatically when the charge dropped to 9.5V.

First, I took all the grounds and cleaned them thouroughly. This did nothing. Then I switched the #1 (charge) and #3 (A/C) relays on the left fender. This did help somewhat. Now the truck only charges to 9.5V when you start it and drive for 2-6 miles, then jumps around back and forth 5 or 6 times, then goes to 14V and is fine. If the truck is warmed up, it goes right to 14V no problem.
This sounds like the grid heaters... if your not familiar with them, read the "stickey" about cold weather starting and headlights dimming...
https://www.dieseltruckresource.com/...dlights+dimmin g


Quote:
Originally Posted by manureman
I also have lately noticed the starter not energizing when I hit the key. I've got electrical power to it, but have to tap it a few times. Is this the same issue or different? Also in the last day or so the truck is not cranking over very fast, like the battery is low on juice.
This could be one of two things. 1) the starter solinoid is going bad and not engaging, when you "tap" it, you are jarring the starter gear into engaging. However, if the battery is low, it may simply not be getting enough"ummph" to engage...



Quote:
Originally Posted by manureman
Lastly, this all started happening about 4 weeks ago, when the serpentine belt broke while driving home from work. I had to limp the truck about 2 miles before I could pull over and stop. But it seemed to start and run ok after I installed the new belt for about a week, then my troubles started happening. Nay info where to start looking? Thanks for any ideas, in advance.

P.S. I put a new alternator on it about 5 months ago, and a new battery about the same time as well.


Thanks

Mike

Mike, when you broke the belt, was it dark? Headlights, blower motor and such running? It doesnt take much to realy pull down a battery, and if it is an older or weak** battery, they can get to the point where they never fully recharge or recover.
I recommend you first have the battery tested, not only static charge but cranking amps and "under load". They should be able to check the alt. output at the same time. If that is good, I'd pull the starter and have it bench tested.
Hope this helps.........CD
on edit:
** by weak I mean under-rated for our trucks.... should be a min. 1000CCA deep cycle....1050 CCA is what the factory sent them out with.

 

i think you have(or had) a bad grid heater sensor(or wire) or a sticking grid heater relay. what you describe after the relay switch would be normal grid cycling. cranking i agree with batt frist.
Clark

 

Thanks for all the helpful advice! It turned out to be the positive battery cable had rubbed against the tube from the intercooler to the intake, and was shorting out from time to time. I put some fresh heat shrink over it and re-routed it and it works great! I also was suspect of the starter as a separate issue, so I took it off and put new brushes in it. Contacts looked great. Now it starts and charges like it should! I also checked the CPS and no cut or broken wires, and the gap is right at .050" so I'm good to go! Thanks again for all the help!


Mike