At my wit's end with this electrical problem...

[MikeO]

Truck is DEAD in the driveway now.



Symptoms.

1. Turn key on, voltage drops down to about 9 volts like it is trying to preheat the grid heater. Unfortunately, it doesn't stop after the normal 5-10 seconds.

2. Truck (used to) turn over fine.

3. Voltage would stay at 9V for about 30 minutes then pop up to 14V (normal spot on gauge).

4. There is no correlation between engine or ambient temp and the time needed to return to normal voltage. Use of block heater has no positive impact on time needed to return to normal voltage.

5. All electrical components show that the indicated voltage is the actual voltage as the headlights are very dim and the elec windows barely work. After the requisite 30 minute return of normal voltage, everything works perfectly.

6. At about 25 minutes, the WAIT TO START and WATER IN FUEL indicators come on full and stay on. As I get closer to the time it returns to normal voltage, both indicators starts to flicker... slower and slower until all of a sudden they both just go out and voltage returns to normal.



I have replaced both heater grid relays. I have also disconnected both of them to no avail. Also checked the temp sensor on the intake grid (not sure if it checks intake temp or coolant temp) and it is clearly changing voltages in a manner consistent with the indicated dash coolant gauge.



Battery is about 2 years old but I am replacing it anyway tomorrow just in case.



Any other thoughts?



Mike O.

 

[icman95]

Mike,



You didn't say if you tested the output of the alternator. Do you have a voltage/multimeter you can put on the battery terminals while the engine is running? This would show if the alt. is charging the batteries enough to keep the whole thing going. Maybe you could charge the batteries a bit to get the truck started and then test the alt.

 

[TWorline]

Mike I hate to say this but, it could be the PCM or the connector to the PCM could be corroded.

 

[tugboatphil]

Mike,

I had a tractor that had all kinds of battery/starter related problems several years ago. Checked everything along the entire starting and charging systems. Everything was clean and shiny where it should have been and still all kinds of gremlins. By chance, I found a new ground cable that I had been meaning to install long ago and it got buried under one of my numerous piles of <strike>junk</strike> valuable stuff. Put it on and the tractor started up like new. After doing an autopsy on the old one, I discovered that it had green corrosion along a large part of the cable, under the cover.

But even if it isn't that, can't emphasize enough to check your grounds.

 

[PToombs]

Yup, what Phil said. Grounds are the #1 problem on these trucks. Wouldn't hurt to check the crank pickup too. Clearence should be . 050, check the plug by the head, and look for corrosion.

 

[Skydiver]

Place a 12 volt test light on top of the ground post of the battery. Connect the other side to the block while its running. It should not light up at all. If it lights up fix or replace your ground wire.

 

[csnider]

I learned the ground cable lesson the hard way with my old Chevy flatbed. ground looked good were it was connected both sides so i dissreguarded it as I checked every other thing I could, i was on the job by the way, uhgg. I got the idea to jumper cable my battery neg to frame and the thing started right up! as written earlier my ground cable was corroded under the insulation were you couldn't see it. . Who'd a thought. Worth a try anyhow... ... .

 

[ptmoore]

my volt guage started doing the same as yours a couple of weeks ago. itested the alt. and found low volts so i replaced the alt and fixed the prob. i think the cold snap down here [when heater grids kicked on the first time this year] fried or started to fry one or more diodes in the alt.

 

[GIT-R-DONE]

Try taking a pair of jumper cables from the negative battery terminal and attach it to the cab (door hinges or the like) and see if it helps or makes a difference.

 

[Allnew2Me]

Start with all the simple things first. Grounds, alt output, battery terminals and connections. You may want to have your battery load tested as it sounds like it might be going. It shouldn't take half an hour to fully recharge after you start. If your Alt output were low then it would take a while to catch up and your battery would never be at full charge.