Engine/Transmission (1994 - 1998) Charging system problem? Need advice.

[wmorden]

Had a problem last night on the way home that I would like some thoughts and advice on...



Left work, started truck, headed home, everything was normal, then "gen" light on the dash came on. Looked at ammeter and it was reading around 12 (lower white line) and not fluctuating at all. Pulled over and checked under the hood (with the engine running) didn't see anything abnormal. Got back on the road and drove the last 10 miles home with the "gen" light on and the ammeter not fluctuating a bit. Got home and backed into drive way - when I shifted to reverse the ammeter started to move again and came back up to mid-range of normal, "gen" light stayed on. Shut the truck down and checked under the hood again. Belt is OK, Generator looks OK, batteries meter at 12. 66 V (did not disconnect them from one another to test,) checked all the fuses and relays in the PDC and they looked OK. Restarted the truck and everything seems normal - no "gen" light and ammeter moving as normal. Checked for trouble codes with the ignition key method and got: 12,47, 55. Don't understand the 12, because I haven't had the batteries disconnected in months. 47 is - charging system undervoltage, but the book says that if that code latches then the check engine light should be on. It wasn't, but is the "gen" light the same thing? Do these codes clear themselves after a while or are they latched until manually cleared? This morning everything seemed normal again. Anyone else experienced intermittent issues like this? Anything you can recommend to check? Thanks in advance for any suggestions, sorry for the rambling description.

 

[Garry Verheyden]

That's wierd. I just had the exact same thing happen to my truck last night (First time in 7 yrs that I have owned the truck) But I just did a 5 to 6spd conversion on the weekend. I disconnected the battery to put the spacer on the starter. Everything looks connected properly. The backup sensor was relocated because the pickup is on the back of the 6spd instead of on top like the 5spd. It was hooked up properly because my backup lights work in reverse. I drove home this moning as I watched my volt meter go from 13+ to about 8. 5. I don't know if my alternator is fried or if it's something else. But I hope someone with more knowledgeable will chime in here, because my truck will not start and I don't want to start replacing parts that are not broken.

Garry.

 

[bmoeller]

Garry- What does your alternator fuse in the PDC look like? May be blown. When mine blew, I was only getting 11-12 volts.

 

[Deezul1]

Do the simple stuff first. Disconnect both batteries at the same time and clean all the terminals real good. Prolly not the problem but I have seen some very strange things happen that a good terminal cleaning fixed and besides its cheap and prolly needs it anyway. Also disconnecting both batteries at the same time will reset and wierd stuff the puter has done.

 

[Garry Verheyden]

Bmoellor, I looked at the fuse it looks very clean but I see a spot that might be burned through. It looked too perfect of a line to be burned through, but I will check in the morning when it is more light out.

Deezul, thanks also. I disconnected the battery with the truck running, and it stopped running immediately. It was generating power when I tested it while running, so It could very well be a fuse. If it was a fuse, I have to ask the next question which is , why would the 120 amp fuse burn out??

Thanks guys,I'll keep you posted.

Garry.

 

[kaffine krazed]

clean the pcm connectors and all other connectors in the charging system.

 

[wmorden]

Thanks for the feedback. Mine hasn't acted up again since the other night, but I will go through this weekend and clean up everything good as well as disconnect the batteries for a while to reset everything.

 

[illflem]

changed your oil lately?

Most common cause for the fuse blowing is shorting the oil filter to the alternator with a filter wrench. You usually see the fireworks when this happens though.

 

[bmoeller]

Re: changed your oil lately?

Originally posted by illflem

Most common cause for the fuse blowing is shorting the oil filter to the alternator with a filter wrench. You usually see the fireworks when this happens though.

I did that once.

 

[Garry Verheyden]

I found the problem, Finally!!!

After tracing wires for a few hours I found the main wire that goes from the black side of the 120 amp fuse to your wiring harness to be the culprit. This wire is connected to th heater grid and the alternator. This wire was rubbed through on the shock tower. I would suggest all of you check this out on your Dodges! The wire was rubbing on the shock tower for some time and finally wore right through. When this happened, it blew the 120 amp fuse which stopped the alt. from recharging my battery. Worse than that, the alt. was charging power into my frame( energizing the frame) and the ground wire from the front fender that attaches to the bottom of the brake master cylinder caught fire!!

DEFINITELY CHECK THIS ON YOUR TRUCKS BECAUSE IT IS A FIRE HAZARD!!! The only reason I saw the ground wires catch on fire is because I disconnected the heater grid and started the engine with the hood up on my driveway. Instantly I saw smoke when I started the truck up and shut it down. If I was driving down the road, it would be too late to save it by the time I saw the smoke.

Garry.

 

[Skydiver]

It happens.

When my GEN. light comes on it is because the grid heater relays are sticking.

I just pull one of the small signal wires off of each relay until the temps drop below 25 degrees. Makes tons of smoke when first started on a cold morning with grid heaters disabled.

Tim

 

[Eric_77]

Has anyone actaully had a alt. failure?



My truck gauge would indicate 12volts then 14 volts put a volt meter on it and it was actually varying from 12. 1 to 13. 8 like alt was cycleing. Gen light would come on after about 3-5 minutes. thought I had a bad battery Sears ran a battery/charging system test and shows no charge at idle but about 12 amps at 2k rpm. Anyone know what it is supposed to be? 12 amps sounds right to me (12volts*12amps) 144 watts. By the way truck has 260k on it. time for a new one?



Checked the wires no rubs from alternator-fuse block-battery but oil was just changed (not by me) no burn marks on alt, fuse is intact.

 

[bmoeller]

The alt. is good for 120-136 amps (at least the '97s are).



If the voltage is fluctuating, I would check all your connections at the alt. , batteries ( batt. posts and the other end of the ground cables), engine to the body grounds, and connections at the PCM first.



It could maybe be the alternator but the PCM controls the voltage, not in the alternator, so that is another possibility.



Don't know if a battery temp. sensor would cause problems or not.



**EDIT- Just had a thought, does it do it right after starting the truck or all the time? Could be the grid heaters cycling.

 

[Monroefiredog1]

Grid heater relay sticking?

Where are the grid heater relays located? I have a 96 that is experiancing a very similair problem. Any help will greatly apperciated.

 

[ronco]

Monroefiredog1, since the grid heaters are supplied with a heavy gauge wire, you should be able to trace the wires from the heaters to the relays. I don't know where mine are located, but that's what I would do to find them.





Ronco

 

[illflem]

The two relays are about straight down from the rear of your driver's side battery on the wheelwell.

 

[Monroefiredog1]

Alt now charging

MY alternator is charging now, I felt so stupid, I had looked at the Alt fuse, but it didn't seem to be blown. So I assumed it was something else. After a few hundred dollars of replacment parts, It still was not charging so I decided to check the fuse with a test light, and low and behold, it didn't have power going to the alternator. I finally found a fuse and replaced it and it worked. What had happen was that the brushes in the alternator were completley worn out, when that happened the shorted out, blowing the fuse. Had new brushes put in the alternator before replacing the fuse. Thanks for all of your help... . this is a great resourse. .

 

[cartman]

when you are haveing intermitent charging watch your volt meter when it is not charging go and tap on the altornator if it starts to charge than the problem may be worn brushes or sticking brushes and by tap on the alt. you are causeing them to make contact with the slip rings, and you need new brushes