PDA

View Full Version : Electrical/charging problem



Shameless Elmer
04-14-2009, 02:59 AM
Hello All, :hail:
I have 98 Dakota R/T that doesn't/isn't charging the battery. The alternator and battery are new (one week old). When the battery is fully charged it seems to run okay, or so that is the story I'm getting. I have witnessed the gauges going from full scale to zero instantly, then back to full scale. With a fully charged battery the gauges seem to work okay, at least while I was briefly looking at them. The oil pressure gauge seems to be the exception. It drops to zero when no accelerator is applied. When the rpm increases to ~1500 the oil pressure gauge pops up to 40 psig. I'm also told the transmission isn't shifting right. It is difficult to get accurate details on this as it is a teenage female driver. I can't tell if she means the transmission itself isn't shifting right, or if it isn't idling down when rolling to a stop. I believe both statements are true. This R/T has a 360 in it.
I understand there is not much concrete information to go on here but, any direction would be helpful.
Thank you all in advance for your assistance.

BluRT00
04-14-2009, 05:14 AM
Pop off the plastic cover on the relay box on the drivers side under the hood. Where you see the 2 heavy gauge battery wires go into it. Check the fuse that is bolted to those terminals. You might have arched it when you put the new alt on/ battery. This would cause the alternator not to charge, I had this happen to me once.

Shameless Elmer
04-14-2009, 09:17 AM
Pop off the plastic cover on the relay box on the drivers side under the hood. Where you see the 2 heavy gauge battery wires go into it. Check the fuse that is bolted to those terminals. You might have arched it when you put the new alt on/ battery. This would cause the alternator not to charge, I had this happen to me once.
Thanks for the tip BluRT. I did pop the cover a couple of days ago but that was to check the ground connection under it. I noticed it was fused but I was thinking past the obvious stuff... like a blown fuse. So you think the odd gauge behavior and shift/ idle stuff might be a result of low voltage at the computer and unable function properly?
Also, on the alternator there is a small black box that the batt. (-) cable runs through. This cable, I believe, is one that comes from the fuse block you mentioned above. I didn't trace it out all the way but I believe the routing is... battery negative post- fuse block- black box that grounds to the alt. case (and then I believe it goes to engine ground). I didn't trace it from the alternator down. I noticed this when I replaced the alternator and thought the charging problem would be solved with the new alternator.
Is this black box just a splice connection to connect to the alternator, or is there something molded into it that could have failed? Is it for noise suppression and nothing to be concerned with?
I'll check the fuse and trace the batt. (-) cable to the block... or where ever it goes.
Thanks again.

BluRT00
04-14-2009, 05:41 PM
You are correct one of the ALT wires does trace back to the fuse/relay box. My gauges acted screwy too when it was low on power. On the back of the alternator you still have the plastic guard on it. Where the big wire bolts down to the back? Just throwing ideas out there, and as for alternators. The remains from Autozone/ Autolites never lasted more then yr with me. I ended up going back to OEM and it has never failed me. Just pricey!

ThundeR/T
04-14-2009, 05:55 PM
check for splices in the wires and corrosion, the wires rot from the inside out,any kind of crack,split etc will allow moisture in,i know it sucks but if you want the problem to go away you have to start checking wires if everything else is ok:goodluck:

Shameless Elmer
04-14-2009, 08:14 PM
check for splices in the wires and corrosion, the wires rot from the inside out,any kind of crack,split etc will allow moisture in,i know it sucks but if you want the problem to go away you have to start checking wires if everything else is ok:goodluck:
Thanks again- I believe the wiring is in good condition, but I'll check. I'm curious to check the fuse you mentioned in your first post. It seems like a good candidate. I'll let you know what I find.

ThundeR/T
04-15-2009, 12:35 AM
lol wasnt me that posted it,i just chimed in:jester:

Shameless Elmer
04-15-2009, 01:49 AM
lol wasnt me that posted it,i just chimed in:jester:
I had a fairly detailed description written and was previewing before posting then.... poof, it was gone. One stinking keystroke!!!!!
Anyway, The truck idles down exactly like it is supposed to. It doesn't shift like it's supposed to though. The diagnostic code says there is a shift solenoid problem. I believe it identifies the wrong solenoid though. It says 1-2 shift solenoid. I believe it's more likely 2-3 solenoid. It'll run 50 mph pretty well. Seems if it were 1-2 solenoid it would be really wound up at 50 mph.
The above code is P0753.
Another error code,P1765, says transmission 12 volt supply relay control fault.
The third error code isP1682. It says ECM has detected a voltage difference between two circuits.
These might explain the shift problem but not the charging or odd gauge behavior. I measure 12.4 volts on each side of the fuse link from the alternator in the fuse box. The oil pressure gauge reads 40 psig above ~1500 rpm. However, when slowing down the pressure falls to zero when the rpm gets to about 1500 rpm.
It seems there are too many unrelated problems for it not to be a common source. Is the ECM causing all of these problems? Does the ECM control the output of the alternator?

ThundeR/T
04-15-2009, 02:38 AM
i had a dsm "mitsubishi eclipse gsx" with ecu problems it was known for those cars to go bad, strange things would happen the caps would leak in the ecu circuit boards and fry other components that were leaked on....this could be the problem. see if you can smell anything comming from the ecu like rotten eggs or burnt. if you have a spare ecu or one local swap it to see if anything changes....best of luck