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Discussion Starter · #1 ·
:help: Alrighty...1990 Dodge Ram, 1/2 ton, 318TBI, A904. 3.21 rear.UNK miles...odometer broke @138K. Probably 200K plus. Charging issues. New 120amp alt. year old 780 cca battery tested good. Cleaned starter and all connections. New 2gauge ground wire. New terminals. Sometimes volts fall so low that the check engine light comes on. Had to jump it 2x last week. Even when charging decent (still not halfway up volt gauge), volt needle will move with slightest load, (taillights, blinker, etc.). I was told the power feed wire could be bad...any thoughts?
 

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i would check all the connections again and make sure there is no rust or anything. if there is no rust and all connections are good i would look into the regulator or the alternator. either one of them will cause it not to charge. good luck
 

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Discussion Starter · #3 ·
Changed the alternator for a brand new 120amp. Same issues. can't find voltage regulator. Haynes manual said on firewall.....couldn't find it.
 

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V6RAM said:
Changed the alternator for a brand new 120amp. Same issues. can't find voltage regulator. Haynes manual said on firewall.....couldn't find it.
well i would definately try to find that voltage regulator. i say that is probably your problem.
 

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Unfortunately the Haynes manual is incorrect in that aspect. The voltage regulator is actually part of the ECM. In other words, to fix the regulator you need to replace the whole ECM.
 

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Discussion Starter · #6 ·
I am hoping it's the power feed wire, the insulation and exposed wire look kind of rough.
 

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You can bypass the ECM and connect an external V/R into the circuit if that is the problem. Use a DVOM and get an accurate reading of the voltage.
 

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I am having exactly the same problem. What external V/R can be used to bypass the ECM for this alternator, and do the leads to the ECM need to be connected to a resistance to prevent the engine light from coming on?
 

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Having same issue...

Started with the check gauges light came on and the voltage gauge needle wasn't working. Cut the truck off, then restarted it same thing. found a fuse in the engine compartment wes blown the power something or nother 20 amp fuse. Put a new one in, then the gauge worked again. Only for about a couple of minutes then same thing checked the fuse again it was fine. I've replaced the alternator, Battery, Engine relay all fuses and wiring are fine. The check engine light hasn't came on at all. After a restart the gauge will work everytime though it's not as high as it should be, at a idle it will remain the same but if you turn on the headlights or A/C it will drop down and the check gauge light will come back on. While driving the truck it sounds like if the throttle was sticking or revving high, also wants to hold gears before it shifts. All this started with the charging issues. I think this similar to the issue posted here wondered if anybody had any suggestions... Thanks in advance for your help... Smartandtwisted
 

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If you pull the error codes off the computer you will probably show a code 41...that means the VR in the computer or wiring to the computer is shot.
Might look thru this article for some ideas. Also I don't see why you could'nt wire in a cheap regulator like this into the circuit. $14.99 at AutoBone or NAPA MPEVR38SB($15) you would also need the pigtail that plugs into it, ECH VRC38 at NAPA.($8)
http://www.carkb.com/Uwe/Forum.aspx/gmc/3134/alternator-circuit-question

 

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no codes stored in the computer..... when checked no errors or codes in history.... the check engine light never comes on so if you check it you get nothing. you will only get an error if the ecu find one and stores it... It's at the dealership it is a bad ecu, they say its a enternal ground issue. probably due to a power surge too much voltage shorted out the VR.... Thanks for the reply..
 

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Discussion Starter · #12 ·
Well I cleaned some connections, had the battery retested (one bad cell) replaced with a 1000CCA battery, still have a few connections to clean. Still having issues, not as severe. Guy at battery shop opined that it was a short in the gauge cluster....I dunno. Changed to 10w-40 oil from 15w-40 for easier cold weather starts....this is winter after all.
 

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Do you have around 14.2 volts at the battery with the truck idling?
Did you replace the positive cable and if you used the "emergency" type cable ends they will not ensure good connections over the long run. Battery cables corrode and oxidize under the insulation. The only proper repair is to replace them entirely. there may also be a ground wire that goes from the battery to the radiator support, is it there and clean? Is your positive cable one of those funny looking ones with an extra connector on it?
 

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