Long story short the other day I was driving down the road and I'm wiring harness shorted somewhere and melted because the previous owner replaced the fusible links with wire. Now my harness is trashed and the key switch is fried. My computer was already bad and not working.
So I'm trying to figure out if I should find a new harness, key switch, and computer or do a rewire and eliminate the computer in the process. Has any one done the computer delete and used the factory dash cluster?

 

Maybe this will help.....

"De-computerize your Dodge" - Dodge Ram, Ramcharger, Cummins, Jeep, Durango, Power Wagon, Trailduster, all Mopar Truck & SUV Owners. Dodgeram

 

The two Batt+ wires feeding the factory key switch (the A1, a 12ga red that powers some dash stuff, and especially the A2, a 12ga pink/black wire that powers the A/C and power windows) were under-sized and over-fused until about 1996 when they offered a replacement pigtail with 10ga wires. The weakest point was, of course, the fusible links.
If the P.O. had hard wired the blown fusible links, it may have just melted, not shorted. Not that it makes any difference. Still a melty mess.
I too am in the process of deleting the computer and putting things on simple, manually controlled circuits.
T.C.'s link is helpful as well as Jim Lane's stickies.
It's the 5v source for the speedo and the 8v source for the factory tach that have me scratching my head now.

 

My 93 did the same thing a few years ago. I decided it would be cheaper and easier to rob the harness out of a rusted out parts truck. Laid it out on the shop floor and went through it fixed some bad spots with solder and heat shrink and reloomed it. I don't think that is a word but you get the idea. The old harness was melted together all the way up the steering column. I found it was easier to swap the whole dash rather than take the wires out of it. But my parts truck ended up having the same color interior. For what its worth the computer from an automatic truck works with a Getrag but not sure if you can go the other way.

 

T.C.'S link helps a bunch, but is the speedo not 12volts? I thought it just needed a ground. For the tach I've been thinking about removing the tach and going to an aftermarket one.

 

I thought about doing this but I am having a hard time finding a parts truck, and I am not sure that a computer that is 24 years old will last much longer.

 

I ran the the tach system with 2 magnets 180* apart on the balancer, and then a magnetic pick-up. Had this on my 89 motor....worked great.

 

Do you know who the maker of it was?

 

True the computers are getting old but I think that the biggest problem with them is the wiring to them and the connection.

 

I have an Isspro that I got from Geno's that came with everything I needed to install it in my 90.

 

That links suggests that the computer is maybe just supplying a ground to the speedometer.
It actually gives 5 volts to both the speedometer and the speed sensor (via circuit G7, which is a 20ga white/orange wire coming from terminal 47 on the brain box, which then splits off at a splice, right above the brake booster, going through the grey connector at rear of engine to the speed sensor, and going also through the firewall bulkhead connector to the speedo) as well as supplying a ground through circuit K4, an 18ga black/light blue wire coming from terminal 4 on the PCM, which is a common ground for most of your engine-mounted sensors.
Is that as confusing to you as it is to me?

-Niemand

 

So if the sensor has 5volts and ground going to it how does it send a signal to speedo? It only has two wires on it.
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Yup that is where I got my set-up from as well.

 

Beats me. I don't get it.
I only know because my speedo started acting up intermittently a few weeks ago and I've been going through the FSM and probing, testing, isolating, and swapping everything involved with the speedometer. I think it's either the gauge itself or the PCM.

 

Mine has been cutting out, and jumping speeds randomly as well...but usually only when the outside temperature is -15*C or colder. It can stop working for 5-10 miles, then pop back to flawless operation. When it's jumping on/off the Speed never jumps higher then the actual road speed. I'm betting my money on a bad VSS.....going to replace that and see what happens.