The Stovebolt Site Forums The Shop Area The Electrical Bay Charging system problems again!!

About a month ago the 38 started experiencing charging problem upon restart. It would charge OK when started cold but any restart during the day, even if the engine was allowed to cool would show a lack of generator output until the engine was run for a few minutes.

A couple of days ago it failed to charge at all, even cold start. Following a trouble shooting procedure recomended by someone else I pulled the Field wire from the regulator and grounded it under a mounting screw. I got in the car and started it. After letting the oil flow for a bit I ran the speed up to about highway speed and the ammeter never moved off of just above full discharge. I was told that indicated a bad generator. If the ammeter had shown a charge it would have been a bad regulator.

I turned off the key, reattached the Field wire & pulled the regulator cover. I checked the voltage at the Battery terminal with everything off & it showed 6.1 volts. I started the engine and using the idle screw ran the engine up to about highway speed. It showed about 5.9 volts then. The regulator cut-out relay was not engaged, I'm assuming because of the lack of voltage. When I manually pushed the cut-out relay to the closed position the generator started to charge and ended up charging at a 7.5 volt level.

I assume the way it's supposed to work is as the engine speed increases, the generator output increases. The voltage at the Battery terminal of the regulator increases which causes the cut-out relay to close, allowing current to flow through the regulator.

If I'm correct that all makes sense and the lack of voltage at the Battery terminal would indicate the generator is bad. What confuses me is IF the generator is bad, why does it start charging OK if the cut-out relay is closed manually? IF the generator is OK as indicated by it's ability to charge once the cut-out relay is closed, why is there a lack of voltage at the Battery terminal UNTIL the cut-out is closed manually? Electricity makes my head hurt!!! :confused: :confused: :confused:

yeah really! been tryin to get folks to understand that pain!

sounds to me like it might be your regulator cutout is the problem, and it's function is really to prevent generator voltage to a battery that's already charged - I don't think the gen will put out full voltage until there's a load - not sure on how to pin point the fix tho

Bill

I agree with Bill. Sounds like the cut out is goofy.

Have you tried a different regulator?

Maybe your regulator isn't hooked up right or your generator needs a better ground. Unless every electic item is turned on, you shouldn't show a deep discharge on the ammeter even without the generator charging. I only show about a two amp discharge at idle, at which time the generator is not charging and the cutout is open.

It's the second regulator I've tried. My understanding of the working of a cut-out relay is that it's a simple electro magnet. At battery voltage there isn't enough current through the windings to create enough magnitism to pull the contact points shut & close the circuit, energizing the regulator. As the generator spins up, the output voltage increases to the cut-out relay coil, increasing the magnetic pull which closes the points allowing current to flow through the regulator and all is good.

What's happening with mine is no matter how fast the generator spins it won't put out enough voltage to pull the cut-out points shut. With the engine running at highway speed there was barely 5.9 to 6 volts at the battery terminal. The cut-out relay has to have 6.2 to 6.7 to close. The cut-out relay on my regulator is set to close at just above battery voltage. 6.1 volts will not close them. That way they aren't closed with the engine off, draining the battery.

Doesn't the generator HAVE TO put out more voltage as the speed increases if it's working correctly? The faster the windings move through the magnetic field it HAS TO put more electricity doesn't it???? God my head hurts.

yes the gen will gen more the faster it goes, but you don't want that to reach the battery alla time - if the batt is up to full, the gen output hasta be cut out to prevent blowing the battery up

I'd think the 'feedback loop' hasta work both directions, that is if the batt is low, the regulator allows the gen charge to reach it if the gen is putting out enuff - at idle a generator will usually not have enuff output to charge the batt - once the batt reaches whatever the setting is [maybe 6.5-7V?] the generator should be cut off no matter how much it's generating

not sure on the setup of the 38 [ not like this I hope! ], but read thru this and see if it helps - who'da thunk there'd be a tech tip on it?

I've read the tech tip before but it's incomplete. The info I need will be included in future additions to the article.

My 38 originally used a third brush generator and two coil (cut-out, voltage regulator) regulator. That had been disposed of before I got it. It's now set up with a later model 6 volt system using the standard three coil regulator (cut-out, current regulator, voltage regulator). Because of that little in my 38 manual deals with the system I now have. From what I've been able to find out by reading everything pertinant that I've been able to find. The cut-out is mainly to disconnect the battery from the generator when the engine is off and reconnect it when it's running. The feedback loop is handled by the current & voltage regulator coils.

The problem I'm having trouble getting my head around is the fact that there isn't enough voltage to close the cut-out points with the generator running over 1500 rpm. The rest of the voltage regulator is isolated from the charging system and therefor play no role until those points close. At 1500 rpm the generator should be putting out far more than the necessary 6.2 volts.

There's obviously something going on here my feeble mind isn't grasping. Thanks for the ideas, I'll get it figured out some day.

Tiny,

I know you have done some research on this problem. Although Hotrod Lincoln isn't too active anymore, his info lives on...go to the electrical forum, and using the search function, under member name, type in Hotrod Lincoln..all his dope on generators and troubleshooting them pops up....no BS with this cat!

Stuart

Back when I first got my truck, there was a charging issue. The Ammeter always was on discharge, and every once in a while the damned thing would crap out.

The truck would run off of the battery because the gernerator wasn't putting out enough juice. Though, a bonus of that was I got to go back to the farm (I never went more than a mile away, so it wasn't too bad of a hike) and got the tractor to haul the old girl back to the quanset for an appointment with Doc Charger.

I ended up pulling the generator and using some VERY fine sandpaper to clean up the armature and the brushes. Reinstalled it and I haven't had a problem since.

[knocks on wood]

There should be curent at the bat. term. on the regulator at all times. Mayby you have a loose term.on the back of the gauge or bad amp. gauge.

I once ran a '50 Chevy without a voltage regulator 'cause I couldn't afford to buy a new one.((student + kids + wife) = no bucks)) This got me to school, work, and home for 3 months.

I ran a pair of wires into the cab, one from the field terminal and one that I grounded to the generator, connected a 20 ohm 50 watt rheostat between the wires (which I had from a old DC train set power supply)and hung the whole mess by the wires from the steering column.

I would set rheostat to zero ohms (shorted) to start and low speed running around town and would adjust the rheostat to keep the ammeter charging by one needle width when running on the highway.

Oh yeah, always parked it on a hill for a drift start because I couldn't afford battery either.

Conclusion: IF the generator is good it will output voltage just by grounding the field terminal - no regulator needed. Check that first. Then, if there is no output by grounding the field, check the brushes and clean the commutator as posted earlier. Probably wouldn't hurt to replace the brushes to make sure they are the correct length and don't 'hang' in the brushholders without making contact. Also check all the internal connections to make sure they are OK.

A good commmutator will be sort of a 'choclate'color, not blue, which means that it is burnt by arcing. Arcing means there is something wrong with the brush system, worn too short, bad brushholder springs, bounding from a worn commitator. etc.

If the commutator is dirty and/or worn, clean it up and make sure the mica insulation between the segments is slightly below the surface so the brushes don't 'trip' on them causing the brushes to bounce and not make good contact. This will cause arcing and burn the commutator prematurely.

You can drag the tip of a thin knife blade along the mica to scrape it away if it is too high. We would also grind the 'set' out of a hacksaw blade and use it instead.

Make sure the generator is working before you waste time and effort on the regulator.

Hope this helps,

52 Ted

Ya caught me in one of my human moments. Instead of saying "why is there a lack of voltage..." I shoulda said something to the effect of "why is there insufficiant voltage...". All it shows is battery voltage even with the field wire grounded.

What voltage does the GEN terminal indicate with the engine revved and the field grounded? You did repolarize the generator, right?

Tiny,
you don't need to read the battery voltage when you are trying to diagnose this, you need to read the GEN or Armature voltage. With the cutout open and the field solidly grounded, your Armature/Generator voltage would go to around 20 Volts. When the cutout closes, the voltage cannot possibly go that high because of the battery and the regulator.

I would suggest disconnecting and taping the GEN and FIELD wires at the regulator. Then ground the field at the generator, start it up and measure the voltage at the armature. If that is good, you have issues with either the regulator or wiring. Running a ground wire between your generator casing and the regulator housing may solve your problems.

Baldy, I did repolarize the generator.

Baldy & truckernix, I may have misunderstood because I've been checking the voltage at the Bat terminal. I'll ground the field terminal and recheck at the Gen terminal. Either way there isn't enough voltage to close the cut-out. This will only take a few minutes & I'll post the results.

OK, I grounded the field wire at the regulator & fired her up. I set the multi-meter on DCV at the 20 volt setting. Running at fast idle the meter showed 0.00 volts with the positive probe on the Gen terminal/wire and the negative probe grounded. I checked the continuity of the field wire and the generator/armature wire just to make sure there isn't a problem there and they checked good.

Tiny,
I think that it would be helpful if you grounded the field right on the generator and then measured the armature voltage right on the generator. That would definitely tell if the generator is OK. If you have a poor ground at the regulator it could produce all the symptoms that you have described. So I would recommend testing the generator by itself first.

The problem turned out to be the generator. I took it back to the guy that rebuilt it. He said the comutator showed arcing & was dirty like the brushes weren't seated well. He cleaned it up, put new springs on the brushes & a new pully end bushing in it. Now it works like new. Another plus, when I was fiddleing with things trying to troubleshoot I fiddled with the old Delco-Remy regulator that was on the 38 when I bought it but wasn't working & got it working again (cleaning & adjustment). Now I have a working charging system and the correct regulator. Life is good!