Attention: TDR Forum Junkies 98.5 24v 5 speed 201k miles, daily driver since new
1.My fairly new batteries went dead, due to extreme cold causing the lead cable ends to come loose. I fixed them and charged the batteries but they went dead again along with all of the instruments failing except for the tach. Even no speedometer. My handheld voltmeter indicated no charge from the alternator, but it tested good at generator repair shop although still not charging. I was told that the the voltage regulator in the pcm failed. The truck runs good otherwise so long as I charge the batteries and don't use headlights.
2.I drove it straight to an automotive electronics shop specializing in computer repairs who has fixed other computer related problems on gas vehicles of mine over the years He tried to find the source but after attempting to locate the bad module he gave up, saying that he can't acquire Chrysler specs and schematics for the Cummins Diesel and this system is quite a bit different from the gas engine cars. He confirmed failure of voltage regulator but can't find what module controls the instruments nor whether all exist in single PCM/ECM box or are separate plugable modules that could be replaced.
3.I have read other threads and see that I can put an external voltage regulator on and bypass the PCM but that won't get the instruments and speedometer working. If others can confirm this is a simple fix, I will proceed.
4.I have many years exp. as computer systems engineer & understand how control systems software are developed and could probably even read the code, but can't find anything so far on this system that helps solve this problem other than in these forums.
5.What module controls the instrument panel and can it be replaced independent of other modules or will replacing the main computer module with a used one fix the problem, eliminating the need to have someone debug the system to pinpoint the the failure? What little I have found indicates that there is a 5 volt dc supply that powers the instruments and maybe even the voltage regulator, but nothing further can be found about this.
6 Last note: This was probably caused by a defective old commercial battery charger that I have used for around 25 or more years. I was told that it is probably leaking a/c voltage into the DC and damaged the computer module.
1.My fairly new batteries went dead, due to extreme cold causing the lead cable ends to come loose. I fixed them and charged the batteries but they went dead again along with all of the instruments failing except for the tach. Even no speedometer. My handheld voltmeter indicated no charge from the alternator, but it tested good at generator repair shop although still not charging. I was told that the the voltage regulator in the pcm failed. The truck runs good otherwise so long as I charge the batteries and don't use headlights.
2.I drove it straight to an automotive electronics shop specializing in computer repairs who has fixed other computer related problems on gas vehicles of mine over the years He tried to find the source but after attempting to locate the bad module he gave up, saying that he can't acquire Chrysler specs and schematics for the Cummins Diesel and this system is quite a bit different from the gas engine cars. He confirmed failure of voltage regulator but can't find what module controls the instruments nor whether all exist in single PCM/ECM box or are separate plugable modules that could be replaced.
3.I have read other threads and see that I can put an external voltage regulator on and bypass the PCM but that won't get the instruments and speedometer working. If others can confirm this is a simple fix, I will proceed.
4.I have many years exp. as computer systems engineer & understand how control systems software are developed and could probably even read the code, but can't find anything so far on this system that helps solve this problem other than in these forums.
5.What module controls the instrument panel and can it be replaced independent of other modules or will replacing the main computer module with a used one fix the problem, eliminating the need to have someone debug the system to pinpoint the the failure? What little I have found indicates that there is a 5 volt dc supply that powers the instruments and maybe even the voltage regulator, but nothing further can be found about this.
6 Last note: This was probably caused by a defective old commercial battery charger that I have used for around 25 or more years. I was told that it is probably leaking a/c voltage into the DC and damaged the computer module.
