When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hi,
I have a '93 which i drive infrequently. I was aware that the battery was discharging much faster (truck just sitting there) than usual. I intended to use the truck the next day so I hooked up the charger and left it charging overnight. I attempted to start the truck the next morning but nothing. I connected jumper cables and started it after a couple of minute. After a couple of minutes I disconnected the jumper cables and noticed an unusual sudden change in rpm; I don't recall if it was up or down. Several seconds later the engine stopped. I hooked up the jumpers again but nothing. No lights, nothing. I checked the battery voltage and it read 6 volts or so. My guess is that the alternator was trying to charge a battery with shorted cells and something blew. I haven't been able to locate a wiring diagram so I'd be grateful it if someone could point me in the right direction. Also, I appreciate hearing any suggestions as to how I should proceed. Thanks.
Jim F.
This sounds a lot like a bad connection. Or the alternator isn't charging.
Using a multimeter set at 20 volts dc check the reading across the 2 posts of the battery (red lead to +, black to -). You should see 11.5 to 12.5 v. With the engine running you should see about 14.5 v. That would indicate that the alternator is charging - less than about 14 it's not charging enough, much more than 14.5 means it's charging too much and will fry the battery.
Clean all the connections at the starter, solenoid, battery and also the ground where it connects to the engine and frame. Shiny clean and tight. Also the ground on the fender by the battery and the rad saddle by the washer bottle. Make sure the cab to intake manifold ground wire is good as well as the cab to frame ground at the right radius arm bracket.
That's a start anyway.
Hi Chris,
I didn't make it clear in my previous post but immediately after the engine quit I disconnected the battery and it read 6 volts. I feel certain that I had shorted cells and that by leaving the charger on overnight I was simply overcharging the remaining cells.
I temporarily replaced the battery with a known good one and even the engine compartment light did not come on. I may have additional problems but as a first step I want to find what is causing that light not to come on. I didn't state it but with the replacement battery nothing electrical worked. A wiring diagram seems to be my first need.
Jim F.
The 3 extra wires on the rear post of the solenoid feed power to the truck and accept power from the alternator. Start there.
This is most likely a bad connection somewhere. Clean them all first before you start messing with the harness and wiring diagrams.
Hi Chris,
I realize your advice is well meaning but can you provide assistance with locating a wiring diagram? With the alternator trying to charge a battery with shorted cells may well have produced a "bad connection" I'm flying blind without a decent diagram. Judging by the number of posts you've made it seems very likely that you can provide assistance regarding the diagram or let me know if my quest is unreasonable.
Jim F.
Could write a book to explain how it all works. What you need to know is that the alt. has a power output - the black with orange stripe on your diagram. It should be putting out 14.5 volts dc when the truck is running.
That's on a 3G alt. Earlier style has 2 or 3 wires but they eventually join into one.
No matter which style alt. you havethe power output will eventually end up at the rear post of your solenoid on the fender - the one with the larger red wire that goes directly to the battery. You should also have 14.5 volts at that connection as well as at the battery + post.
So before even starting to mess with the wiring, you would need to determine if the alt. is actually even charging and if so is that charge getting through to the solenoid post and through to the battery post.
Hi Chris,
That sounds like very worthwhile info. Unfortunately, I'm not to that point in my troubleshooting. With the old dead battery with the shorted cells completely out of the circuit and power applied through jumper cables from another car, nothing electrical works. I decided that the easiest first step would be to find out why the underhood light does not come on. Whatever circuit is involved must be open. This is just the first step but will hopefully point me in the right direction.
While referring to the wiring diagram and tracing that lighting circuit I noticed the 2 alternators depicted. I'm at a loss as to how to understand this. On all vehicles prior to this truck I've had the shop manual and never had to rely on generic info. It seems logical that I have one or the other but the wiring diagram doesn't seem to show that. With the wiring bundled and from my first serious look it appears that the top alternator shown is what I have. Understanding what's going on is not really important to my first troubleshooting step may come into play further down the line. For now can I safely assume that I have one or the other?
Thanks, Jim F.
The top one appears to be for a 3G alt. That's the one with an internal fan. 92 had the earlier version for sure - the one with the external fan, 93 is probably 3G but not necessarily.
If you are getting 0 power, you should check your connections and your fuses in the power distribution box.
Hi,
My thanks for the assistance provided! After replacing the battery all works fine. I'm at a loss as to what I did wrong during my troubleshooting. I had the hot lead disconnected from the original battery and connected jumper cables from my car's battery to the negative post of the truck battery. I connected the positive to the, now floating in air, positive truck connector. The underhood light did not come on as I had expected. I assumed something open in this simple circuit, probably indicative of an open effecting other circuits. Couldn't find any opens with my ohmmeter so replaced the old battery and all worked fine. Learned a lot in the process; mainly about how much I still don't know about this truck.
Jim F.
12-03-2016, 01:58 AM
Wiring diagram?
