VCCA Home Forums TECHNICAL - GENERAL Electrical - 6 volt Voltage regulator adjustment

Hello All,
I want to be sure that the voltage output of the voltage regulator on my '51 is correct. I just need some assurance that what I have done is the right way. I attached the positive lead from my digital volt meter to the BATT terminal and the negative to a good ground. I ran the engine for a while to get it warm and took a reading which was 8.3 volts which I know is too high. There is a screw on top of the far lefthand "coil". Is that the voltage adjuster? The service manual shows 2 different different VRs. One the same as the one I have, which I know to be the right one for the car (1108301) and 1 with the adjusting screw at the bottom of that coil. The manual says that the cover must be on when taking the reading. Why? Does the '51 have a cut out relay? The service manual says that the optimum voltage should be 7.4 volts. Thank you for your help.
Jeff

Checking voltage with the cover on will give a more accurate reading for 2 reasons. The primary one is that it maintains a consistent temperature around the electromagnetic coils in the regulator. The resistance in the wire in the coils does vary slightly with temperature.

The other (which I did not think is as much of a concern) is the magnetic field shielding effect of the metal cover. Each of those coils creates a magnetic field.

The cutout function is integrated into the relay. There are 3 coils inside the voltage regulator. It really is more than a voltage regulator. One coil is for voltage control, one for current regulation, and the third is the cutout.

Rusty,
Thanks for your quick response! So what I should do is to adjust the voltage with the cover off and then replace the cover, let the engine run for a bit and check the value again.
Jeff

That is the approach I would use. Check the voltage, remove the cover, make the adjustment, then reinstall the cover.

If you can, check the voltage after you make the adjustment and before you reinstall the cover. Then check after the cover is reinstalled.

I am interested in what difference it actually makes if any. My thinking is that under some ambient temperature conditions there will not be much difference.

Beware of using a digital meter for this.
Some are confused by the electrical noise on the lines.
If it looks right, it likely is, but they often go wild on car voltage measurements.
WL

I will get back to the car after the weekend and do the test again as suggested above and report back. It seems that the meter (a cheap Harbor Freight unit) reads pretty good and steady.
Jeff

I would be cautious with the really cheap Harbor Freight meters. My experience with about a half dozen of them is that they do not give stable readings. The reason I have had that many is that these use to be the “free” gift with your purchase.

Even just checking battery voltage can be interesting. Using them to measure resistance is even more fun. I tired to calibrate the fuel sender in my ”˜37 with one. That was a mistake! I still use a couple of them but only in situations that do not require accuracy or stable readings. I gave the rest away so people would quit borrowing my good meter.

There are 2 actions that seem to improve the stability of the reading. One is to put a new brand name battery in the meter. The second is to turn the meter on and let the circuitry warm up for at least 10 minutes.

I also have about 10 of hese as I also got the free with purchase. I agree that they re nit all that accurate but for checking continuity and nbattery voltage they seem to be good enough. I have an old analog meter that is quite good so maybe I should redo the measurements with this one.
Jeff

I encourage you to use that older meter. You are trying to measure a value that does have some fairly rapid variation as the regulator cycles. I would be cautious making the adjustment you are doing while using the cheap HF meter.

You are on the right track and thinking things through very well. I know you will get it figured out.

Use the old analog meter if you can, but if you are measuring charging voltage, you need to know down to the tenth of a volt, and many analog meters have not even close to enough resolution.

On some 6 volt cars a Harbor Freight meter wont work, and my more expensive digital meters (Tektronix, Fluke) wont work either, they just lock up. I had enough grief from this that I built an special analog meter from scratch for this purpose.

If the Harbor Freight meter isn't locking up, count your blessings. Connect both the HF and the Analog meter, and if they agree then read the voltage from the HF one for the extra precision.

Only believe readings taken with the cover on. The voltage will be different with the cover off.

Except for trusting the absolute value displayed on the HF unit, I think that it is operating properly. Using both together is a good idea, Does it matter that the gauge in the car registers just a hair over center when car has run for a time? It goes about half way to right after cranking a cold engine having sat for a long while but goes back to center after a few minutes.
Jeff

Jeff, Check that the 7.4V "spec" is measured at the battery to assure proper charging, not just the Batt terminal on the V/R. Measure at the center of the positive post, not the cable terminal, engine running at fast idle (as I'm sure you know). You may find that the voltage there is several tenths lower due to the slight resistance in the various connections and wires, and the V/R may be set about right.

Doug

Doug,
Thanks for the advise. I will check as you suggest. The service manual instructs to measure at the BATT terminal so that's what I did. I will do more tomorrow.
Jeff

Jeff, Understood. Minimum voltage measured at the battery is 6.9V in order for the battery to charge.

If you need to change the V/R setting by anything more than a tweak, the process is a bit involved. See the attached Delco Bulletin 1R-118 copy, which is appropriate for the V/R in the '51.

Doug

Make sure you are not adjusting the air gap. Some of the old regulators don’t have an adjustment screw for the operating point and they must be adjusting by bending one of the two spring tangs. That is very tricky.

That is normal expected behavior. The gauge in the car registers current. Since there is a voltage regulator, and the system voltage is held more or less constant, the battery will draw less current as it gets more charged.

Update: I used a high quality digital multi meter and my analog multi meter and got an adjustment of 7.2 volts at idle and 7.4 at high RPM as per the service manual. The reading was consistent with both meters and, in fact, with the HF unit so all is good. The final reading was with the cover on. Thanks everyone for your help.
Jeff

Excellent! Thank you for letting us know the results.

Glad you got it sorted out.