Technical Voltage question

I have a 1954 3100, just rewired with an EZ wiring harness, and a Ron Francis closed loop ground harness. It is still on a 12v 35 amp generator.

On the first drive, I noticed the voltage was all over the place regardless of engine speed, from high 12s to high 14s. Putting a load on it with headlights for example did not change this, really variable. Monitoring on a brand new Stewart Warner gauge. Prior to the rewire, it didn’t have a functional voltmeter so I don’t have anything for comparison.

I bought a new regulator from Classic Parts for my application (mistake?) and now it is stable but seems to be overcharging. With engine at idle, or revved up, it stays above 15. 15.1-15.2 to be exact. Putting a load on it with headlights drops to about 14.8.

I confirmed the gauge accuracy with my digital voltmeter and the gauge is spot on. Right before firing up, the battery had been on a battery tender.

What is safe voltage for these trucks and what would be the first thing to go in a bad situation? Battery? Should I be calling Classic Parts to see about refund?

Let me know your thoughts. Thanks in advance!

 

Old style Voltage regulators can be adjusted as I did it in the 60’s when I worked the battery line a Sears. It must be done carefully using needle nose pliers on the spring hooks. After each adjustment you MUST put back on the cover even if your just holing it on while you rev the engine slightly to take readings. It’s been a long long time but the spring need slightly less spring tension. To most it’s a “dark art” and most mechanics would never touch one especially ones that the cover is riveted on.

 

I'd want something around 14-14.4V. Too high voltage will likely reduce battery life, lamp life, and probably generator life too (as the charging current goes up at higher voltage, the load on the generator also goes up).

 

some of the delco generators (on IHC tractors) were adjustable as to out put. If I remember right, you could slide the one brush closer or farther away from the other brush. i watched my Grandpa do it on his 1946 M.

 

Another question is when are you getting these readings? Right after startup, or well warmed up? Voltage will always be high right after startup to replenish the battery, but should settle into the high 13 to mid 14v range warmed up and operating. By nature a generator does not charge as well at low rpms like idle. So if you have a decent electrical load like lights on, it will cause the voltage to go down and then back up as engine speed increases to replenish the battery. In other words you get more voltage variation with a generator than with an alternator. Since alternator is more capable of meeting the amps required at low rpms.

 

I'm assuming you have a 3 unit regulator. When you take the cover off you will see a simple relay with just one set of points. That is the cut-out relay. You then have two units with dual points, that is they have upper and lower points. One is the voltage regulator and the other is the current regulator. The difference is that the voltage regulator has fine wire around the core while the current regulator had heavy gauge wire. Like Jimmy Six said, you need to adjust the spring tension on the voltage regulator. Be very careful when you replace the cover as it is easy to short things out. You will know if you do.

 

I'd probably very carefully clean the contacts in the old regulator, and put it back on, and see how it does.

Volt meters were not used when generators were common, ammeters were used instead. There might be a reason for that?

 

thanks for the question- the reading was as stated when cold but did not settle down after running for 20 minutes and warm.

 

Regulators used to be adjustable to set charging volt rate. Does this new regulator have a removable cover, and have you checked for adjustments in it?

 

Ok, I’ll disconnect the battery and take a look tomorrow.

 

Realize that you have to adjust the regulator with everything connected and the engine running. Set it with a voltmeter across the battery, then put the cover back on and let it's internal temperature normalize. If the voltage stays where you set it, you are good to go. If not, you have to try again.

 

ah, got it! Working today and checking this thread when I can- I’ll try to get after it tomorrow with both the old and the new and report back.

 

it's usually a good idea to disconnect the negative battery cable, before removing the regulator cover, and then again before installing the cover. Just so you don't make sparks...

 

14.4 is the desired full charge voltage when it is charging the battery back up after you start.
After the battery is charged up you might see anything from just over 12.5 to 14.2 depending on the demands of the system and what you have on. As long as the battery stays fully charged and isn't being drained because the alternator isn't putting out enough amps to keep up with the demands of the system life good.
That 15.1 is a tad on the high side though and might boil the battery dry after a while.
One thing I would suggest is having the output checked with a battery/alternator tester To make sure that your gauge isn't over optimistic on the volts being produced.

 

Thanks for posting. Good info, I didn’t double check the gauge reading with the engine running across the battery terminals with a digital voltmeter. All checked out perfectly, gauge is spot on.

what you were saying about the 12.5 to 14.2, maybe the regulator ain’t doing that bad.

 

Thanks man, good to know.
Quite honestly, I’ll likely try putting the old one back in and cleaning up the three wire contact points a little and see what she does first. My dad had obviously put this one in at some point, it looks brand new under the cover, literally.

 

For cleaning the contacts, after you disconnect the battery, I take 600 grit wet or dry, cut a strip about 4” x 1/2” fold it in half the the long way, and drag it thru the contacts a few times one way. After that I “polish” the contacts with paper pulling a strip thru.
I’ve started using “air-in-a-can” for computer keyboards for final cleaning on many items like a regulator or other relays.

 

Insomnia is a pain in the ass. So I got up early and pulled the cover off the new one and the old.

The old one has screw adjustments for the springs, the new one doesn’t, just springs on tabs that are preset.

Old one:

And the new one:


With the non-adjustability of the new one (or at least with the necessity of some kind of a hack), I think I’m going to just clean up the contacts as others have suggested and adjust as necessary.

 

Remember after you tweak the tab, set the cover back on before you take a reading with the engine running. It does make a difference. We had adjustable ones back in the 60’s also, they were never as good as the fixed ones....

 

Good to know

 

Well, Friday fails! I cleaned the contacts VERY gently with some 1000 grit and got some gnarly black stuff off the contacts so that wasn't helping anything. Now the voltage flickers all over the place and is mostly discharging. I think I got the air gap a little too big on the cutout relay possibly, after removing some of the junk, since the other two are making constant contact as they were before and had no residue on them at all. Time to switch to the new regulator and try to adjust the spring arm to a more correct tension I'd guess in the absence of a feeler gauge that I can look up a manual and see where it's at. But I should probably have one of those anyway.

If anyone reads this as a lurker and is having same issues, here's a YouTube video I found. Most guys who have posted would feel like this is kids stuff but even though it's a "tractor" voltage regulator, it's the exact same setup that I have.

 

Ok, I just read what I wrote- to clarify, the original regulator, before I cleaned the contacts today didn't flicker back and forth from 12-14.5 erratically. It just flowed up and down over the course of a drive so-to-speak. So there was definitely a change for before vs. after I cleaned the contacts.

 

@Crazy Steve , is it correct for voltage gauge to fluctuate randomly when measuring generator output?
Please see above posts by OP.
Thanks.

 

So, back to the new regulator.

tweaked the voltage regulator spring a tiny bit, loosened the spring tension. Down to 12.2v.

Added back a bit of tension, back up to 15.1. Tiny tweaks, super sensitive. I’ll get there

 

This is one reason I don't use generators.... LOL

No, it isn't normal for voltage to randomly fluctuate. What I suspect is the 'cleaning' of the cutout relay contacts actually made it worse, not better. If the OP got 'gnarly black stuff' off the contacts they're probably pretty burned and a 'gentle' cleaning likely only knocked off the high spots, reducing contact area. My experience is if you're cleaning a set of contacts, you need to remove ALL pitting to restore good contact and proper performance. These contacts are usually tungsten and hard surfaced for wear so it takes some serious filing to clean them up, preferably with a points file. The contacts should then be burnished with fine sandpaper or crocus cloth to insure even contact. The regulator will need adjusting afterwards.

 

The best advice about adjusting voltage output on a generator regulators is "Don't". If you insist, get in the shop manual and read up on them. A piece of sandpaper dragged through might get you going again out on the road but the contacts are now permanently trashed and will likely burn up. The cutout and voltage adjustment procedures aren't brain surgery but there are certain setups and specific steps that must be followed in a certain order. Another thing to keep in mind is when generators ruled the roost, digital voltmeters didn't exist. The specs for those generators were developed and published using old school test squipment. For a couple different reasons, it is important to use a good quality analog voltmeter when working with generators.

Charging voltages aren't set in stone, they are temperature dependent and vary widely. Generator charge voltage set points are higher on average than alternators. 15 volts actually isn't out of line when it's cold out.

 

Okeedokee. I found this online shop manual- been reading up, good stuff. http://www.ruiter.ca/mc/info/PDFs/1R-116.pdf

 

A poorly grounded regulator would be erratic.

 

Once you get the hang of adjusting the mechanical regulators you never want any other kind. The adjustment is very sensitive. I like to get the voltage to 14.5 1000 rpm or higher, 13.00 at idle..

They also make a solid state regulator that really do an excellent job of keeping the right amount of current going to the battery..

Getting the right charging rate is important to battery life..

 

Who is "they"? About the only option I've ever seen is to use a Bosch Volkswagon regulator for a 60s era generator equipped bug, but they wouldn't look right, for those who care about such things.

Somebody brought up bad or lifted grounds, that's a good point. Before messing with regulator output make sure there aren't any defective grounds or corroded connections. Burnt or stuck brushes at the armature itself could cause erratic swing in voltages too. There's a few things to look at first.

Good quality voltage regulators are hard to find these days, try not to bugger it up by ham-fisted "repairs". Somebody here once allowed they worked at a dealership back in the day, with a huge stable of mechanics, and he said they only let 2 specific guys ever work on customer car voltage regulators.

The voltage setting adjustment is definitely VERY touchy. I sort of determined with the spring tension it's similar to tuning a guitar string, adjust the voltage down well below your set point, and then bring it back UP to the target voltage.