Having an intermittent problem with my 1995 12v lately. It's loosing overdrive while driving down the road and also the ac stopps cooling at the same time. The overdrive on/off button does not light and has no function when this occurs. I can manually lock the converter in 3 when this occurs. This happened first Tuesday night leaving dinner and by the time I got home, 5 miles, and turned it off in the driveway, they do switch light was working fine. Tonight we went to dinner and everything worked as normal but when we left dinner, it never would shift to 4. I pulled over and unplugged the factory temp sensor with no change. Drove to Cheesecake Factory and when we came out the od switch was functioning normally again along with the ac blowing cold but the trams temp light was flickering so I pulled over and plugged the temp sensor back in. Trans shifted normal for about 2 miles and then started dropping from 4 to 3. I locked the converter and it kept dropping from 4 lock to 3 lock and then back up and down for a few more miles until it lost 4 completely and no ac. Every time this happens, I loose control of the od on/off switch and ac cooling. 

Check fuse 9 in the cab. It might be cracked and opening and closing the circuit as it heats and cools. As you'll see it covers the PCM, A/C and OD circuits.

 

Thanks Mike! I will check it out this afternoon and get back to you

I thought I had it figured out. My Fass and all my gauges were wired into #9 so I removed the gauges and retired them to another fuse.  Drove it down the road a few miles and then to dinner with no problems. Came out of dinner and same problem over again. Stopped at redbox for a movie and swapped out fuses in #9 and turned the key on to see if the od off light would illuminate, it did so I thought all was good. Rented movies and came back to it not working again. Idk what to do and I really hate electrical!

I think I would rather pull a 20 year old oe hub bearing as chase electrical gremlins. That or just put my hand on an anvil and hit with BFH. 

Unplugged the pcm harness and cleaned them up with electrical cleaner and then dielectric grease and went for a test drive for about 30 min with no problems. Came home and let it set about 15 min and went back out to test it out and it's not working again. It's as simple as turning the truck off and back on and it starts messing up until the truck is cooled off again. I'm lost

Found something interesting tonight. Drove the truck to a friends 10 min down the road with no problems and of course after setting there for 30 min, no od light and no ac. Drove home in 3rd and popped the hood when I got home. The ac dryer is covered in ice and the ac was in the off position! I removed battery terminals just for fun and of course it didn't change anything.

Any advice? I'm going to dig into this thing tomorrow and really haven't a clue where to start.

Wish I had something to offer but I am unqualified.

On 8/3/2016 at 7:27 PM, 98whitelightnin said:

I removed battery terminals just for fun and of course it didn't change anything.

 

The whole removing the battery terminal does nothing the ECM or PCM modules are flashed with software and cannot be altered by simply unhooking the battery. If you want to reboot the computer a simple key off for 10 seconds or so and back on with reboot all computers. 

 

On 8/3/2016 at 7:27 PM, 98whitelightnin said:

The ac dryer is covered in ice and the ac was in the off position!

 

You've got a short in the compressor trigger circuit. Not to mention it might be under charged not normal for the system to ice up. Even on low fan it should only sweat never freeze. Low pressure switch might be faulty and low on charge. 

 

I'm starting to wonder if the ignition switch is failing to energize that circuit or the contacts are weak on that side. 

I have never seen the compressor frozen up like that before, even when actually running the ac.

Drove the truck for an hr today and lost overdrive about 40 minutes into the trip but the ac is working fine. I'm thinking this is a pcm issue 

Might want to do the AC noise test. 

 

 

My buddy was driving the truck yesterday and it was messed up and not going into 4th.  He started shifting manually and accidentally hit neutral and when he brought it back into D, everything was working normally. 

Ended up having more problems like tach falling to 0 and all gauges going crazy. Replaced the pcm and all is good

Good to hear. What did you use for a replacement?

Now being its electronic device failure did you do a AC noise test? I do see any results of a AC noise test done. Don't risk your new PCM to the damaging AC noise problems.

 

Funny so many people thing that they can escape the electronics of the 24V system by going back to a 12 valve trucks or p-pumping 24 valved trucks. Still is other electronic modules and an alternator. As long as there are electronic devices and alternator present then electronic device can fail from AC noise issues. 

Don`t want to hijack this thread, but why is it that alternator AC noise issues are so prevalent on 2nd Gens? There may be issues on 3rd Gens as well ? but I haven't noticed any on this site. 

32 minutes ago, angus said:

Don`t want to hijack this thread, but why is it that alternator AC noise issues are so prevalent on 2nd Gens? There may be issues on 3rd Gens as well ? but I haven't noticed any on this site. 

 

 

 

 

 

AC noise issues can affect any vehicle with computers / electronics. The thing is AC noise issues manifest in different way for each vehicle and generation. Like a Chrysler Pacifica it will show up as a speedometer error. It will show speed even though you not moving. Like my truck is manual and it affect the cruise control with surging up and down.

Edited August 28, 20168 yr by Mopar1973Man

I actually sold the truck to my buddy and I told him to do the ac test but I'm not sure if he ever did it. Found a pcm from a local guy with a 95 2wd truck, it's the same part number but the only difference is the 4wd light doesn't illuminate. Truck runs great!