Voltage Regulator

I have a 87 dakota, that I put a 2000 dodge ram 5.9 engine in.
The trucks voltage regulator had been replaced several years ago, with a Standard VR125.
I am not for sure which alternator I have. Looking online at rockauto, they show 117 or 136 amp. Cant find any numbers on the one I have.....
I am reading 14.96 volts when running (900 rpms)
I think this should be more like 13.7-14.3. volt range
Should I replace it with a different style or model number?
I didnt think it would be a problem, but wanted to ask

Usually the VR is NOT the problem. The VR MUST accurately "see" battery voltage. Check the voltage between VR and battery. To do that "get to" (in the harness) as close electrically as you can to the blue wire going to the VR. Turn ignition to "run" with engine stopped. Measure between VR IGN source and battery POS terminal. Do not disconnect anything "backprobe" a connector to get into it. You do not want to see more than just a few tenths of one volt, say, less than .3V

Now check the ground. Get the truck running long enough to "normalize" the battery--warm and after starting, and charged. Run this next test first will accessories off, and again with lights, heater, etc powered on

Stab one meter probe into the mounting flange of the VR. Stab the other probe into the top of the battery NEG post. You should read almost nothing, zero would be perfect

Usual causes:

Most often, voltage drop in the harness suppling VR IGN (power) terminal
Less often, ground
Much less often, problems with the battery itself, or a bad VR. Most VRs fail rather than "go off" just a small amount

OK, measuring from the blue to the pos. terminal, (engine off, switch on) read .33 volts
Measuring from the voltage regulator case to the neg. terminal I got .01 volts at idle.
Turned on everything I could and got .09 volts.
Tomorrrow, I am going to take the ground strap (engine to firewall) loose and clean at the firewall. Already did it at the engine.
I think, the local Advance auto can test the VR if I take it off.

Any other suggestions are appreciated!!
And thanks for taking the time to write such a detailed response.

Don't know about the 87 but if you are using the 2000 alternator, 2000 Dakota/Ram, the charging system is computer control.
My sister had one that was having charging issues. We found out that under the battery box was a temp sensor that told the alternator/regulator how much voltage to charge the battery. We replaced the sensor and all was normal.
That's all I know about 2000 Dakota's.Just a FYI.

Those reading look OK. One question...........at what point did you get the "almost" 15V reading? If the battery /VR was still a bit cold it could have been so. That reading is not TERRIBLY high but is getting there

One last thing, this is the 70/ later "flat" electronic VR, right? If so, the connector/ connection at the VR might be suspect, pull that apart, examine, look for corrosion, etc, and "work" it in/out several times to scrub the terminals and to "feel" for tightness

If you can "drum up" a known good battery (maybe out of another vehicle) you might drop that in and be sure the batteries are "up."

If nothing else just "throw the money" and replace the VR. This can happen, but rare

Today at work, I was thinking about the connector at the voltage regulator. Ill take it apart and clean it. I can swap batteries as well.
I agree, dont want to just throw parts at it..... But I think one of the local auto parts stores can test regulators off the truck.

Before I do anything else, I will take the truck for a drive, and then re-check the readings, starting with the battery at idle.
Thanks again!

Darter6 said:

Don't know about the 87 but if you are using the 2000 alternator, 2000 Dakota/Ram, the charging system is computer control.
My sister had one that was having charging issues. We found out that under the battery box was a temp sensor that told the alternator/regulator how much voltage to charge the battery. We replaced the sensor and all was normal.
That's all I know about 2000 Dakota's.Just a FYI.

Click to expand...

The 87 dakota used the standard 70? and up mopar regulator mounted on the firewall. Basically I am using the engine and front accessories from the 2000 ram. But have a carb, and a HEI ignition. So no computer with a built in regulator. Just using the 2000 alt. and the 87 regulator.
Thanks