Bad TPS, No Grid Heater

[NYChris]

My truck has had some minor quirks ever since I bought it a year ago. These are things I have worked around with no problem but would like to get to the bottom of things.



First off, I think my TPS is just shot. I had no O/D right from the start, but hotwired it to make it work. Just haven't gotten up the nerve to drop $160 for one yet. The grid heater won't cycle either. Turn key to RUN position, no click under the hood, no light in the dash, nothing. Could the heater problem be related to the TPS malfunction? I know when probing around the wires to the transmission with my meter at the time I hotwired the O/D, I did get the heater to cycle once, so I know it works. That also made me think the two were connected somewhere in the wiring harness.



What's the deal... TPS... relays... or something I haven't even thought of?



Chris

 

[cguthrie]

I would think that the problems wouldn't be related. If you wired around it and all you have to do is push the o/d off button to turn it off i'd say leave it like that if you don't really mind pushing the switch. I've talked to one guy that did this and left it like that. When my TPS was going out my grid heaters were still working but it never completely went out though. BTW the price from Cummins is alot better than dodge i paid around $210 for mine. Did you check your fuzes for the grid heater, i'm not too sure if it's got it's own fuze because my service manual is in Oregon and i'm in Korea. Hope this helps out a little.



Chris

 

[1stgen4evr]

Grid and OD prob

Both of these functions are controled through the PCM (power control module) that is located in behind the battery. It also controls the voltage output on the alternator and cycling of the air conditioner.



I own a 92 D350 that has exhibited problems with the grid heater and OD as well as the alternator control and air conditioner. The OD problem has existed since the firsts time it was driven in the rain. I am suspicious of the wireing but I have not been able to nail the problem. I have the wrap off of most of the harness and have the color code chart on various wires.



I have the OD on a switch taped to the shift lever. There are post regarding this where the owner has installed the later model lever with a switch in the end. The computer on early model trucks does not have the ability to indicate where malfunctions exist. Trouble shooting in this regard is quite difficult.



I am shortly going to change the automatic to manual and have simply wired around the air cycle function. There are other controls that will cycle the compressor when it is cold enough. The computer allows or disallows air conditioning when other motor conditions are acceptable. The Cummins doesn't care if the compressor is on or off. There are after market controls for the alternator where you can install a regulator on the back of the alternator.



Sun coast in Fla says that they can make the OD function correctly no mater what. They must have the experience to do it. The solution I am taking is to do away with all computer functions. I will have some in cab controls to make the grid heater cycle with a momentary switch. (Hold to run) The air will cycle with pressure switch interrupt that is already in the circuit. I won't try to detail the wires to connect as I don't want the liability.



The TPS is a piece of crap and was when it was new. It might be good enough for a tiawaneese boom box volumn switch but will not take the vibration of the engine for much of a service period.



The truck is tough and if you have the money you can make it work like original. But not for long. You are going to have to make some of these things happen on your on. One solution would be to wire it like the 89 and 90 without a computer.



1stgen4evr

James