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Bob S
Dodge Dakota
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4/03/2004
13:29:08
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 Subject: '94 V6 overcharging?
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Message:
Hello all,
I got some great help here with a hard-to-diagnose bad fuel pump recently, so I'll try my next problem as well...
I have a high-mileage '94 V6 Dakota. It is consistently overcharing under all conditions. Voltage gauge on dash shows high charge and check engine light is lit. Self-test throws a 46 code ("Charging voltage too high too long").
Truck cranks fine and battery voltage seems fine when not running (13+ volts). Voltage at the battery while engine running with no additional load is high (18+ volts). Voltage across the alternator field coil (small posts) seems normal (5-10v relative to load), but the alternator ouput terminals (big posts) show too much voltage (18+ volts).
Any thoughts on possible diagnoses, or other problem areas I should check? I've seen some references to a battery temp sensor -- but I think maybe this is only on the later generation Daks? If I should have one -- where would it be on a '94? Doesn't look like there's anything under the battery.
Thanks to all in advance for your help.
Bob
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Greg
Dodge Dakota
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4/03/2004
15:24:23
|  RE: '94 V6 overcharging?
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Message:
I think all my dakota has ever put out on the alternator when I checked it at the battery post after startup is 14.something volts... Never as high as 18+ and most other vehicles won't put out that kinda voltage either... AND you battery voltage should be right around 12.6 volts, not 13+... It's 2.1 volts per every cell of the battery and 12 volt batteries are 6 cell which actually makes them 12.6 volts... Most batteries will run 12.3 volts to 12.6 or 12.8 at the highest in some cases, so this sounds like your alternator is really overcharging... May just be a relay in the alternator stuck open to a constant charge instead of regulating itself like it's suppost to do... May just be time for a rebuilt one or go ahead and get a new one... Have you had any of the free diagnose places such as most auto parts stores check it out??? Might want to try that for starters to help with the diagnoses process before you do get into replacing things...
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Bob S
Dodge Dakota
JOIN HERE
4/03/2004
17:12:36
| RE: '94 V6 overcharging?
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Message:
Greg,
Many thanks for the response. If I find the fix, I'll share it here. Thanks again.
Bob
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J and J Auto
GenII
4/03/2004
17:29:29
| RE: '94 V6 overcharging?
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Message:
There is also on some trucks a batt temp sensor
that tells the comp what volts the system is
shooting for.
Located under the batt on the tray if your truck
was equiped with 1 my 95 has it don't know if 94
did or not.
Alt bad or comp controls system voltage bad in
computer have seen this condition a few times
only it was always low system voltage
Larry
J&J Auto
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Bob S
Dodge Dakota
JOIN HERE
4/04/2004
04:44:44
| RE: '94 V6 overcharging?
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Message:
Larry,
Once again, thanks for your respected advice. I'll pull the battery and see if I can find any sensor or mounting location. I looked and felt all around the tray (with battery) and couldn't find any wires or sensor -- maybe it's missing altogether???
Thanks again.
Bob
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if
Dodge Dakota
JOIN HERE
4/04/2004
04:51:21
| RE: '94 V6 overcharging?
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Message:
that does not work u can always throw a set of under drive pulleys on it and that would slow down the alt some...
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Bob S
Dodge Dakota
JOIN HERE
5/18/2004
15:24:28
| RE: '94 V6 overcharging?
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Message:
Thanks again to all for your great advice.
I've replaced both the alternator and the battery (which was cooked). Neither fixed the overcharging problem.
I did find a good tech article which helped me do some troubleshooting, even though it refers to a later model Dakota:
http://www.asashop.org/autoinc/sept2001/techtips.cfm
I was able to find the wire from the SBEC to the alternator which carries the field current (green wire) as described in the article. Cutting this wire killed the overcharging, which would tend to indicate that the problem is either in SBEC or the battery feed wire to the SBEC. I cannot figure out which wire this is.
Does anyone know the color or pin of the wire which feeds battery surface voltage to the SBEC on a '94 Dodge Dakota V6?
Thanks again. Will post my results here.
Bob
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