During the blizzard Tuesday night I am trying to go to town to get brushes for my tractor starter. Well as I am driving I notice the head lights are getting brighter. I look down at the charge guage and its pegged at 18. I turn around and nurse the truck home.

SO now that I am plowed out by my neighbor, I need to fix the truck. What is the consensus on this repair. Pay the long dollar for a new computer which is plug and play or go the external regulator route based on the sticky.

I have no issues going either route, as the factory computer lasted for 130,000 miles. What else stops working if the computer totally craps out. This is a manual transmission 4WD truck. Computer is $220

Going the external regulator route is no issue either, basic wiring. New aftermarket regulator is $14, pigtail plug is $8 plus some time and wiring. I realize most members are going to go the $22 route becasue its cheap, but I just don't want to rewire and then have to replace the computer later for some other reason. Thanks.

 

I'm surprised the CPU only went 130,000 miles.
You might want to look into the possibility of a bad diode or some other issue, like a possible issue with the battery and connections.

Try diagnosing the symptom before applying a cure.

Mark.

 

I would go the ext. regulator route.... and incrementally phase out the need for the computer.

 

This kind of thinking is EXACTLY why the wiring in these trucks is usually all screwed up.
Not meaning any insult towards the original poster, but why is it noone wants to FULLY DIAGNOSE THE ISSUE before trying to fix the problem?
It's not always the ECM/PCM that is at fault.
It's usually the LAST item to blame.

Mark.

 

I hate crappy wiring too... I painstakingly do a good job. I'm an electrician and I don't like electronics in my vehicles - go figure.

 

We know the crank sensor failure would not cause the over charging condition. In this case the only thing I can think that would casue overcharging, gage pegged and headlights very bright would be the regulator correct?

 

Have you ran it since the overcharge state?
Have you had the battery checked?
It's not hard to pull the alternator and have it bench tested.

It's kinda' hard to just say it's one particular thing without checking others.

Mark.

 

I'd get the altonator checked first myself.

 

the alternator has output, thats all it does, its working, the regulator can have cold weather adverse affects, so can loose ground and hot wires, check to see if everything is tight and clean

 

My knowledge is very limited but i think A 1993 the ecm/pcm controls and monitors...

A/c (If you have it)
Alt/Charging system ( 92-93)
Speedometer
Overdrive (Auto Only)
Tachometer ( If wired to factory wiring plug 92-93)
Wait to start light
Water in fuel light

If you have a scanner for older trucks you could check your codes. Or do the key on, off, on, off, on, trick to cycle the (check engine)codes on the dash. You might get a code relating to the alt/charge circuit.

I have read about people loosing just the charging circuit. Sounds like that might be the problem... But like I said my knowledge is very limited. Good Luck

 

The WIF/WTS sensors are direct wired and not integrated into the ECM.
Neither is the tach, though it's primary voltage (7-9 volts) comes from the ECM, it's tone signal comes directly from the CPS and is read by both the ECM and the Tach.

Mark.

 

When my ecu is plugged in I get WTS,WIF, and the grids whine and click.
When my ecu is unplugged I do not get WTS,WIF, or grid heat . So I figured they were related on a 93.

So the ecu sends 7-9 volts to the cps, and a signal or tone is sent back to the ecu, then relays that signal to the tach plug under the dash. Thanks

I certainly don't want to give out bad info, just wanting to share what my 93 does with and w/out my ecu plugged in.

 

Thanks everyone, we have a working theory, but before finding this we have some addtional damage. Because I have an Autozone Group 31 battery with studs, you have to screw post adaptors on. The Ground adaptor had worked its way a little loose from the weight of the ground cable this allowed the ground cable to swivel slightly. This intermitent ground we believe was the casue for the weird fluxuating charging voltage. Before finding this I successfully started the truck and drove it to the repair shop where it sat outside for a few days waiting its turn. The voltage was varrying the 3 miles from normal to +18. The shop owner, and my best friend BTW, when out to to start it, turned the key and when the grid heaters & fuel relay came on he noticed smoke coming out from under the hood, drivers fender area. He turned the key off, open the hood and removed the battery cable. The main harness bundle has some damage at about the midpoint on the drivers fender. We don't have it inside yet to examine what has happened. We believe either we had a wire short from abrasion or low voltage (casued by battery connection) increase current and caused a melt down. I will post pictures as soon as possible.

 

Would you mind letting me know what you found. I have a similar issue.

 

My truck is a 91.5 and the same thing happened to me, went for a ride and happened to glance down to see the voltmeter pegged. I did just like you and limped it home. I have another dodge affectionately known to myself as the 5k parts truck so that gave me 2 computers and 2 alternators between the two trucks. I brought both alternators to autozone where they naturally said they were toast but they had a good one to sell me. I bought it and put it on to find nothing had changed, voltage still pegged at anything above idle. So I thought my $5,000 parts truck would give me a little more use by donating it's computer since my research into the matter indicated a flaw in the regulator (in the computer). It worked, or so I thought. It no longer overcharged but the voltage seemed to be lower and lower every day. And the new computer didn't let me use a/c or overdrive. Yes, the 5k parts truck is also an auto 91.5. I brought the truck to an alternator man that claimed it was a common problem on a lot of old chryslers and he fixed me up with an external regulator for around $50 installed. Only thing now is my check engine light is on, charging is perfect though.