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Discussion Starter #1
73 W100 360. no upgrades to the charging system (yet)

Im starting to work on some upgrades to this truck. I started with replacing the instrument cluster VR. as seen here:
http://www.allpar.com/history/mopar/electrical2.html

I was testing the output with a multimeter. i found that the input had 17v. the 5v output was not working. this is another story.

While the engine is running the battery is showing 17v. Sooo that is high. I tested the VR. (see pic) Im gettging 17v on the red wire and 7.8v on the yellow.

What is happening? Why is the charging voltage soo high? I dont understand the readings on the regulator. I tested it on 2 different grounds.
 

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Discussion Starter #2
SO I changed out the voltage regulator and the same results.
 

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Make sure the vr has a good body ground to the battery. If same result pull the two smaller wire going into the alternator and check voltage. You should get battery voltage (no charging). It sounds like it's full fielding witch it shouldn't be doing.

 

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So I unplugged the field connections and the voltage is now around 15.2v

with the VR disabled the voltage dropped from 17v+ to 15.2v.

any ideas?
 

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could have a voltage drop in a connection somewhere which will cause the voltage to run high to the battery.

i hooked up a relay to the battery and ran that to the blue wire (the wire on my truck to the VR is blue) of the voltage regulator. that way the VR is reading voltage directly from that battery rather than through a mess of wires, ignition switch, and bulk head connector.

i've had zero issues with voltage since. it runs at a constant 14.5-14.7 volts all the time for the last few years now. and i've also noticed that my regulators have lasted a lot longer since i upgraded.

trace the yellow and the red wire and see where they go. the wire headed to the bulkhead connector is the wire you need to hook up to the relay.
 

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I just did an ammeter bypass, rewired most of the engine bay, and added a HEI module.

the alternator is still going full field. I like your suggestion to run the VR via a relay to the battery. That is going to be my next step. I dont know how else to track down the rouge ground issue.
 

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I added a relay off the ignition as you suggested. it is still running at 16.5v or more.
 

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The transpo adjustable voltage regulators are still available -- you could use one of those to 'cheat' it down.

After fiddling with mine for some time (it was at ~15.5v all the time on one truck and 12v even on the other regardless of idle speed) I swapped alternators and the voltage followed the alternator -- regardless of which truck (regulator or wiring harness) it was in.

The 12v alternator had a break in a field wire internally -- soldered up and it was fine again with stock regulator. No more issue.

Don't know why the other puts out 15.5v -- but I dialed it back with the adjustable regulator and it's been fine in the days since.

Just get a new alternator -- they're like 20-30 bucks for normal stock type on RockAuto!! If that doesn't work go to the adjustable regulator for 20 bucks.


I still hate the charging systems regardless as well -- I'm doing the first of the two trucks with a 3G Ford internally regulated 130a alternator as soon as I get the time. Have most of the materials already!
 

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Had a problem with mine overcharging also. Turned out to be a bad VR. I tried using the cheaper ($15-$20) ones but still did not work. My 84 W150 /6 has to have the one from NAPA approx. $40 put that one in and back to 15-15.5 volts.
 

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Discussion Starter #10
thanks guys. a couple of weeks ago I swapped out the VR from one at autozone. it did not change anything. since then I have bypassed the ammeter and installed HEI. In that process I have basically rewired the engine compartment.

I guess it is time to change the VR again and also try a new alternator.
 

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Have you had an auto store or mechanic check the alternator function and fields? They ought to do it for free / that could reasonably rule it out.
 
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