ataboy9026

My truck has "check engine" light on. Its code 41. Took off alternator and tested,its fine. Wont charge, guage reads about 7.5 to 8 but batterys go dead after running for a while. Transmission goes into/out of overdrive when cold but seems to be fine after its warm. The tach and cruise both work fine. I was going to change crank sensor but my tach works. Could this still be it? Or the PCM? I switched the ASD relay with the horn relay just to be sure the thing wasn't bad with no change. I read about installing a external regulator from a 79 dodge truck with 318 engine on firewall and was considering doing this to save thr $581 PCM if that is my problem. Should I do this? Anything I can check before taking to dealer? They want $80 just to see whats wrong.

infidel

If you have short replacement batteries and use a spacer under them the battery temp sensor will think the battery is frozen and not charge when it gets cold out.
The temp sender can also fail or their wiring get eaten by acid.
Sensor is under the driver's side battery,.

ataboy9026

thanks for the reply... this problem started before it got cold out. This is a truck I dont drive every day, but this overdrive shifting and charging problem was happening when it was about 60 - 70 degrees out. I've noticed the trans shifting for a while... but the charging is new problem. The transmission was rebuilt about 60,000 ago.truck has 260,000.

RBFD415

ataboy-

I think you may have missed the point of the batt temp sensor tip- if there is a problem with it, it may not matter what the outside temp is?!

Check the recent post/thread "weird alternater" problem. I just had an alternater problem and posted there- I got alot of good info. There were several good links to past posts about charging issues- including using the older style remote (Dodge/Mopar)regulator in place of the PCM (as you mentioned).

Good luck!

got...DIESEL?

for what it's worth, if it IS the PCM regulation circuit.....yes you can use ANY external regulator, not just a dodge one. These Denso alternators have an insulated F1 and F2 (field). So if you find a regulator that supplies negative field, take one of the two field studs on the alternator and give it positive full time. Vica versa for positive fielded regulators. The alternator doesn't care who tells it to charge....its stupid....the reg is the brains of operation. We use alot of transpo D-7014's to convert all types of externally regulated alternators. They are piggy back, self exciting and voltage adjustable. There is no wiring to the truck for it, all on the alternator. Any reputable rebuilder will have them laying around. They were originally designed for the Delco 10 DN's of yesteryear. Should cost about 30 bucks cash and carry. Easy to wire up.

OR......find the problem and fix it, or replace the factory board.

kd460

"for what it's worth, if it IS the PCM regulation circuit.....yes you can use ANY external regulator, not just a dodge one. These Denso alternators have an insulated F1 and F2 (field). So if you find a regulator that supplies negative field, take one of the two field studs on the alternator and give it positive full time. Vica versa for positive fielded regulators. The alternator doesn't care who tells it to charge....its stupid....the reg is the brains of operation. We use alot of transpo D-7014's to convert all types of externally regulated alternators. They are piggy back, self exciting and voltage adjustable. There is no wiring to the truck for it, all on the alternator. Any reputable rebuilder will have them laying around. They were originally designed for the Delco 10 DN's of yesteryear. Should cost about 30 bucks cash and carry. Easy to wire up."


Hey got...DIESEL, sounds like good information, but can you give it to me again
S L O W L Y, and in a very basic description so this average joe can understand it a little better? Thanks, Kevin

ataboy9026

thanks for the info guys... but I checked the batteries and they have been replaced but sit in the origional location and are both good. Should I change the battery sensor or is there a way to check it? Any other advice? Should I go ahead and install the external regulator even if my PCM turn out to be good? If that doesn't cure my problem can I leave the external regulator hooked up?

Crimedog

There is a fuse in between the Alternator and battery, it is located on top of the driver side fender in the black relay box. Can't remember exactly which one, but if you follow the wires from the alternator to the fuse you'll see it. I think it was 100A fuse of something like that.

kd460

Yes, the fuse gets zapped when the hot lead on the back of the alternator gets grounded from most commonly, the oil filter. It's easy to touch it with the filter and bye bye fuse. It has driven alot of guys here crazy trying to figure it out. I am 99% sure it is a 120 amp fuse.

Good idea/suggestion to check that. Could be blown from when switching out the alternator?

The battery sensor can be unplugged without any problems. It just senses heat and cuts down on the charge rate some. I have never disconnected mine, but I have read that others have without any problems. From the top it looks like a black button about the size of a quarter or 1/2 dollar coin. Good idea/suggestion to check the wiring on that.

If the above does not help, then start looking for shorts? I have read that people have had the alternator tested "good", only to end up replacing it nd the problem was fixed. You can also rebuild them yourself for a significant savings. Good luck, Kevin

ataboy9026

That fuse is good. And I checked the 2 terminals to make sure of contact, its good. I also checked the ground at alternator. Its good. There is 12v power at the alternator large lug at all times. So I assume the wires are good from battery/120 amp fuse block.Any other ideas? When we figure this out I will definately post the remedy. Could it be the crank sensor? Even though my tach works fine? Could the crank sensor cause my trans to shift in/out of overdrive when cold? I took the sensor off and inspected it and the connections and re-installed with no change.

Charlie Hardin

See https://www.dieseltruckresource.com/...d=36421#newpost for an external regulator fix for a few bucks. Beats 500 plus for a new pcm.

INJECTOR JACK

You said your overdrive problem was happening before the charging problem. You may have a problem with your tps or the temp sensor it the tranny cooler line. There is a fix for the temp sensor on this site if you do a search as well as info on the tps.

got...DIESEL?

to check the alternator operation on board w/o taking to a shop for testing, disconnect the two small wires on the back (F1 and F2). Leave the output wire attached. Now ground one of the terminals and hook positive to the other. This will full field the alternator and produce 100% output. The voltage may go sky high...16+ volts, so I wouldn't let this state of charge stay long. To help this, turn every power consuming device on the truck on full bore.....high beams, fans, etc, etc. This will load the alternator and bring volts down a little at idle. Ohm's law. Once this is done, bring the rpm's up to 1500, which is enough rpm to let the alternator perform full potential. If the voltage cranks back up again, then you have successfully "load tested" the alternator and it is fine. Back off the throttle and unhook the jumpers to the field terminals. Then go after connections between the field terminals and PCM as well. If, at rpm, the voltage did not rise to at least 13.8 - 14.2, then the alternator has at least one if not more open or shorted diodes in its rectifier. Alternators can have at least six to 12 diodes depending on output rating, 1/2 positive, and 1/2 negative. If a few of these fail, it will still charge, and under light load voltage may seem okay. But a load test will always give them away, and usually a VERY LOUD whine will be heard.

Keep testing and eliminating.

Chris

ataboy9026

I went to local Carquest store and asked for 79 dodge regulator. They knew of this problem and had a conversion kit made to go into my alternator. You simply take the back cover off alternator, hook up a red power wire, and a black ground wire, then there is a green and an orange wire that comes out a "opening" in the cover (actually the cover is dented out enough for 2 wires to fit without pinching) and then hook up the green and orange wires onto the 2 small terminals on alternator. Very simple install. That cured my problem, it charges above 14 now on my guage. But my check engine light is still on. I reset the codes and it tripped again, still code 41. But at least it charges now. The kit cost me $23 and I would assume you could get it at a NAPA or Carquest store. I dont think Autozone or Advance Auto will know what your talking about. There wont be an additional box or wires screwed to your inner fender with this kit. It looks very clean and stock.Nothing to appear aftermarket. Thank all you guys for the great info. I am glad there is a site where folks can help each other without spending $$$$ at dealer.

kd460

Hey ataboy9026, glad to hear its working. Can you post the carquest part number? This sounds like a nice fix. Thanks, Kevin