Gary_Ash Posted August 11 Share Posted August 11 My 1948 Studebaker M5 pickup has been sitting for many months but I finally got it started. However, the ammeter doesn't show charge even when I rev the engine. I think it was working before I parked it some months ago. The ammeter shows discharge when I turn on the headlights, so that part of the circuit works. I cleaned the points on two of the relays in the regulator, still no joy. So, how do I tell if it's the generator or regulator not working? The engine is buried way down in the engine compartment, so it's difficult and painful to get to anything. It would be a lot of work to pull the generator out for testing. The regulator is more accessible. Everything is strictly stock, 6 volt, positive ground. Back in the bad old days, a dealership garage would undo the 3 bolts on the back of each fender side panel and the one under the radiator support and have four guys lift the entire nose off the truck to do any major engine job. With the nose in place you can't see or reach anything on the sides of the engine. Grrrrr! Firewall with regulator and horn relay. Engine before installing fenders and nose. Link to comment Share on other sites More sharing options...
Rusty_OToole Posted August 12 Share Posted August 12 Quick test is to "hot wire" the field of the generator. Usually this means connecting it to power, be careful when you do this it will charge like crazy - if the generator is working. Of course the engine needs to be running. 9 chances out of 10 the points in the reg are corroded, the tenth time a brush is stuck in the generator. 2 Link to comment Share on other sites More sharing options...
Frank DuVal Posted August 12 Share Posted August 12 Gary, you have the shop manual? As Rusty says, look up full fielding the generator. You can do it right at the voltage regulator. If full fielding makes it charge, then regulator is bad. If not, generator. Or wiring to it. Hey, seen any mice? Or squirrels? ❓ The reason for confirming with the shop manual is there are two systems, A circuit and B circuit and they full field differently! Delco usually A circuit, Ford typically B circuit. 1 Link to comment Share on other sites More sharing options...
Bloo Posted August 12 Share Posted August 12 Have you tried polarizing it? 1 Link to comment Share on other sites More sharing options...
TerryB Posted August 12 Share Posted August 12 (edited) A lot of repair manuals suggest first using a wire jumper from ground to the mounting screws of the voltage regulator to make sure it’s well grounded. The regulator must have a good ground to work. Another test is to run the generator as an electric motor to see if the problem is in the generator. It looks like your generator is close to the battery so you might be able to do the test without removing the generator, just remove the fan belt. We recently had a guy on this forum whose generator had a damaged insulator on one of the generator’s terminals. The symptoms showed up as intermittent motoring of the generator. Edited August 12 by TerryB (see edit history) Link to comment Share on other sites More sharing options...
dodge28 Posted August 12 Share Posted August 12 Frank, you forgot mention the fan belt must be removed. Link to comment Share on other sites More sharing options...
Gary_Ash Posted August 12 Author Share Posted August 12 Polarized the generator - no effect. Connected the field and armature - no effect. Took off the brush cover - couldn’t see a #@$&% thing. Unbolted the generator, used a lifting strap to haul the generator out of the engine compartment at the expense of many scrapes to my arms. It looked like insulation had come off some of the old internal wires, possibly letting the armature connection ground to the case. As soon as I finish my lunch, I’ll be off to the alternator/generator/starter service shop in New Bedford, MA for an overhaul. I’ve used them before on old electrical stuff. When in doubt, throw money at the problem. 6 1 Link to comment Share on other sites More sharing options...
DFeeney Posted August 12 Share Posted August 12 Money and time "Well Spent". They don't last forever. Link to comment Share on other sites More sharing options...
Bud Tierney Posted August 13 Share Posted August 13 A bit late,but as per noted above no charge after a sit would suggest checking the brushes for good contact, good spromg movement and the commutator for nice shiny appearance first, if al all reachable... Link to comment Share on other sites More sharing options...
Gary_Ash Posted August 14 Author Share Posted August 14 The generator shop got the job done in less than 48 hours. It needed new brushes, commutator turned, some small parts. They painted the case, looks good. Cost was $185. It needed the work. The shop was amused that they also had a generator from a 1948 DeSoto, same Autolite model, to work on. Now comes the hard work of putting it back in. I just need a guy 7 ft tall with extra long arms and tiny hands to help me lower it into the engine compartment and bolt it in. I should weigh this thing as it's pretty heavy. As I recall, generators and starters will fit in a USPS medium flat rate box, can go cross country with up to 70 pounds for only $18.40. 8 Link to comment Share on other sites More sharing options...
Frank DuVal Posted August 18 Share Posted August 18 On 8/12/2024 at 12:57 PM, dodge28 said: Frank, you forgot mention the fan belt must be removed. I've NEVER removed the fan belt to polarize a generator. There is no need. Just a quick spark and the generator is polarized. Yes, it needs to come off to Motor the generator. 😉 2 Link to comment Share on other sites More sharing options...
Gary_Ash Posted August 20 Author Share Posted August 20 Rebuilt generator installed but still no joy! No sign of charging, discharge noticed when headlights on. I tried flashing the generator again, checked that it motored when voltage connected to armature with fan belt off, tried “full field” connection at regulator. I checked that generator is solidly grounded to engine and battery. With normal connections, ammeter shows discharge mostly, then wiggles between charge and discharge at rapid rate, settles on discharge even if I run the engine a few minutes. Next move is replace the regulator but I hate “remove and replace” method of fixing things. How to prove the regulator is bad? Autolite generator, 6 volt positive ground. Link to comment Share on other sites More sharing options...
Frank DuVal Posted August 20 Share Posted August 20 By full fielding the generator! As noted above. If it charges, the generator is good and the voltage regulator is bad. A time honored test by auto electric shops. How to do it is in your shop manual for your vehicle. Do make sure the wiring is good between the regulator and generator. Do you have a voltmeter? Can you read the voltage of the Armature terminal with the engine running? Sometimes it is easier to attach a wire to the terminal before starting the engine.😉 And read the voltage at the A (ARM) terminal of the voltage regulator. Same reading?❓ 1 Link to comment Share on other sites More sharing options...
Bloo Posted August 20 Share Posted August 20 Full fielding is not quite the whole story on generators because they have cutouts, and if the cutout does not pull in for some reason it still won't charge. Is the regulator well grounded? If you think it's the regulators fault, I'd try dragging brake cleaner soaked paper between all the regulator points, and if that doesn't make it come to life, try carefully dragging a point file (once only!) through each set of points. and see what happens. Of course you want the battery disconnected while you are working on the regulator. 3 Link to comment Share on other sites More sharing options...
c49er Posted August 21 Share Posted August 21 My cars are 1946-52 MoPar 6 volt positve ground. They are Autolite "A" circuit type systems. The way I test for which is the problem...genearator or the regulator is to use a jumper lead and ground the field terminal of the regulator while the is running. Then rev the engine quickly and only for a couple seconds....if the amp meter or voltage meter shows no imediate big positive increase reading then the generator or wiring is the issue. If you do see a huge quick increase of amps or voltage then the regulator is the problem. In my 50+ years with my MoPars usually it's a faulty regulator issue causing a no charging issue. 1 Link to comment Share on other sites More sharing options...
Frank DuVal Posted August 21 Share Posted August 21 (edited) 18 hours ago, Bloo said: Full fielding is not quite the whole story on generators because they have cutouts, ??? The cutout is part of the voltage regulator in these years. The cutout mounted on top of the generator is usually a three brush style generator, with no regulator. 😉 The full field test is to make the generator bootstrap up (due to residual magnetism) and pull the cutout coil in. Edited August 21 by Frank DuVal (see edit history) Link to comment Share on other sites More sharing options...
Bloo Posted August 21 Share Posted August 21 And if it doesn't pull in? Or the points are dirty? 1 Link to comment Share on other sites More sharing options...
Frank DuVal Posted August 21 Share Posted August 21 OK, I see where you are thinking. If I full field the generator and the cutout points are dirty... I condemn the generator when it is still the voltage regulator causing the no charge problem. That's why it is important to include measuring the voltage on the A terminal (or ARM at regulator) when full fielding. Got it!👍 Thanks. 1 Link to comment Share on other sites More sharing options...
Gary_Ash Posted August 21 Author Share Posted August 21 (edited) I ordered a new regulator. Apparently nobody now - or ever - rebuilt regulators. But, now the regulators for old cars are expensive. It was $160 for the right one. Fortunately, I sold $200 worth of 1930s parts last week. In a few days, the regulator will be here. The truck sat for a year, so a few more days won't make much difference. I'm not taking the old regulator off the firewall until the new one gets here, if only to help with reconnecting the wires. I'll be interested to see if the resistors on the back of the case or a fuse element is burned out. My parts catalog for the truck lists the resistors with a Studebaker part number, so maybe people did replace them back in the day. They are shown as Resistance Unit No. 38 and Resistance Unit No. 7. I'll have to Google AutoLite numbers. EDIT: I Googled and found an AutoLite document that included testing, repair, and adjustment of regulators. The carbon resistors are 38 ohms and 7 ohms. Should be as rare as hen's teeth! Edited August 21 by Gary_Ash (see edit history) 1 Link to comment Share on other sites More sharing options...
Frank DuVal Posted August 22 Share Posted August 22 What wattage? Carbon resistors are common electronic parts. Interesting in that AC Delco regulators usually have wirewound resistors on the underside.🤔 Like maybe 20 watts or more. Link to comment Share on other sites More sharing options...
c49er Posted August 22 Share Posted August 22 (edited) Hope your new VR is not a new offshore electronic...weigh 1/2 as much as an original with the wire wound resistors. And last half as long or less.😒 Edited August 22 by c49er Spelling (see edit history) Link to comment Share on other sites More sharing options...
Gary_Ash Posted August 24 Author Share Posted August 24 Got the new regulator. New old stock, that is. It was dated 1970 on the back, has wire wound resistors. Put it in, started up, shows charge. Problem fixed! 10 Link to comment Share on other sites More sharing options...
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