accordivan

I have been chasing a problem on my 98.5 for a while now. If the truck sits for any length of time the batteries go flat, totally.
Yesterday I'm driving along and the "CHECK GAUGES" light comes on and stays on followed by the "AIR BAG" light which also stays on. The CD volume decreases and then quits and all the lights in the radio including the clock disapear. Then my EGT gauge quits. By this time I have turned around and head for home where I park the truck engine running while I unload. When I get back in and press the brake pedal ALL the warning lights in the dash light up and ALL the gauges drop to zero. The engines starts to quit so I release the brake pedal and everything returns to normal except the "CHECK GAUGES" and "AIR BAG" lights stay on and the EGT gauge and Radio still do not work. I notice also that the voltmeter is showing a charge rate of about 12 volts, less than the usual 14 plus. When I shut down and check the batteries they are way down.
Today I pulled the codes and this is what I got. P0216, P0622, P0122, P1693, P0237, P1682. Can anyone explain to me what the **** is going on and what do these codes mean in REAL Language? The only thing I can determine from this is that the Alternator seems to be involved in some way but I'm at a loss to know where to start trying to fix this PITA!

Marine

I don't know about the codes, but you should get a load test done. It definitely sounds like the alternator.

pind

I would pull the alternator and get it tested. Almost 100% certain that will be your problem. Unless you have a real widowmaker of a ground problem. Somehow I doubt that.

accordivan

The saga continues. I fitted an brand new alternator but the system is not charging. When I reconnected the batteris I attached both ground first then attached to first positive cable which caused a spark on contact, so something is drawing current that should not be. If there are any electrical gurus out there I could sure use some guidance right now.

Busboy

Two of the codes were for sensor voltages that were too low. I would look for a short in the engine wire harnesses. Start down by the AC compressor. I assume that all the grounds are in place and if you can't find a short under the hood, I would disconnect the grid heaters and see if that makes a difference. If they are staying on they could pull the voltage down too far for the trucks computers ECM and PCM to function properly. ECM controls the engine PCM controls the alternator.

bent valves

I don’t believe you can trust any of the codes are real. If the battery voltage gets low enough, 8 or 9 volts, the ECM will generate false codes. The circuit inside the ECM uses a reference voltage to make sense of the various sensors. If this reference voltage gets corrupted from low batteries all bets are off on what codes are real.

The first thing you should do is check the 120 amp fuse in the fuse box on the fender. If it is bad the alternator will not supply current to the batteries. If that fuse is good and your batteries have enough life in them to start the engine, start the engine. Does your tach indicate idle RPM? If not the PCM will assume the engine is not running and will not supply a field current to the alternator. The crank position sensor drives the tach and tells the PCM the engine is running. Next check the field voltage on the alternator. This can be measured on the two small nuts on the back of the alternator, bottom nut is positive top nut is negative. Make sure the engine is running for this test. If your voltage reading is lower than 3 volts your PCM is the problem. If the voltage is greater than 7 or 8 volts your new alternator is junk. I am also assuming you have done the troubleshooting in the order I typed.

Oh, I forgot to add, the airbag control module causes the spark you see when reconnecting the first battery. It contains a large value capacitor that will draw a large current when the battery is first connected. After the capacitor charges the current will drop off. You may want to check the current draw (which should be about 0.15 amps or 150 mA) buy removing the negative battery lead from both batteries and then touch one negative lead back to the post and see the high current spark. Then while holding the lead to the post connect a milliamp meter to the lead and post and finally separate the lead from the post. This gymnastic with the lead is needed to avoid spiking the meter with a high current.

Good luck.

accordivan

Thanks a lot guys, you got me started in the right direction. The tach works OK so I don't think there are any major issues outside the charging circuit. I checked to 120 amp fuse which on my truck is a 140 and ???? it was blown which explains why the new alternator is not charging. I'm getting a new one picked up in the morning by a buddy who is going into town (1 hours drive almost, each way). The Dodge dealer has one in stock at $11.85 plus the taxes. I will get that fitted and then take the next step you suggested which is to measure the draw on the batteries. Keep your fingers crossed for me, I'll let you know what I find.

bent valves

I’ll bet after you replace that 140-amp fuse, you will be all set. Hold off on all the other tests unless the batteries discharge again.

accordivan

I hope somebody can learn from my stupidity. I just tried to replace the fuse WITH THE BATTERIES CONNECTED!! How stupid can a guy get?? Fortunatly, all I did by way of damage was blow the fuse and singe the mounting bolt. Now I have to wait until tomorrow for another fuse.

bent valves

Wait a minute, that fuse should not blow even with the batteries connected. There must be a short somewhere. I think you have your work cut out for you trying to find the problem. At this point I am at a loss.

After thinking about the fuse blowing again, the problem must be either the wire between the fuse and alternator is shorted to ground or the alternator is bad. If your truck were in my driveway I would not change the fuse again but put a voltmeter across the blown fuse. If you measure the battery voltage, about 12V, there is a short. Unhook the heavy wire from the back of the alternator and keep it away from metal. Now measure across the blown fuse again. If you see battery voltage the wire is the problem. If you see zero volts the new alternator is junk.

accordivan

Dave, how would you like and all expenses paid holiday in the foothills of the Canadian Rockies with Spring in the air????

I did as you suggested and put a voltmeter across where the fuse sits; bingo! 12 volts, same as the battery. I removed the cable from the B+ terminal on the alternator and 12 volts also. I put a continuity meter across the cable to ground and there was a dead short which, I assume there should not be. This cable has a couple of units attached to it which I think are diodes?? Could these be the problem do you think?

Ivan

Busboy

Are you working in a heated shop since the problem started? If not and you have wet snow it's possible for the slush to have frozen under the power distribution center shorting it out.

Busboy

I was posting while you where but I was just out looking at my alternator feeder cable and I couldn't see anything on mine. I also checked the factory manuals for 2000 and 2001 and it shows just a straight cable from the alternator to the fuse. It looks like a small gauge battery cable with a terminal lug on each end. Why not just replace it with a battery cable run across the top and round the front of the engine clamped in place if yours is supposed to be the same.

bent valves

Springtime in the Rockies. Isn’t that an old movie?
I think we are on to it now. The wire from the alternator to the fuse on my 1998.5 has nothing but wire. If your wire has stuff attached and you measure a ground, that is the problem. The unfortunate outcome of this short is, it may have taken out your alternator. Try this, charge the batteries and start the engine. Leave the blown fuse in the box and the wire off the alternator. Now measure the alternator output voltage at the large stud on the back. If you see 16 or more volts DC you have lucked out and all you need to do is replace that weird heavy wire between the alternator and fuse (and also the fuse). If you see a much lower voltage from the alternator, the diodes have fried due to the short and it will need to be replaced also.

accordivan

I've just posted a picture from my Workshop manual showing the alternator with the attachments at the end of the cable. I hope this helps to identify what they are because to replace that part of the loom is $1200