The Stovebolt Site Forums The Shop Area The Electrical Bay Voltage reg, and alt help

How do I find what amp the alternator on my 58 GMC 1 ton with a 270 is?Getting ready to buy a new voltage regultor and need to know.
Thanks,
Jeremy

Why do you need to know amperage to get a voltage regulator?

Other than that, your '58 didn't come with an alternator. So it's anybody's guess what alternator is on there. Since it has an external regulator and it's in a GMC we can assume someone put a '60s type Delco in it. But they may have put a Ford or Dodge alternator in there. Got any pics?

Somewhere on the alternator housing there should be a Delco part number. It will have 7 digits, normally. Any good parts store should be able to ccross-reference the factory number and come up with a year of manufacture and an amp rating. I can't imagine why they would need to know amperage, as almost all the external-regulator Delco alternators used the same regulator, IIRC.
Jerry

Yes your right it does have a generator.Do they all take the same regulator?If so can you give me a part # ?My local stores arent much help.Any hepl would be great.
Thanks,
Jeremy

No, voltage regulators are matched to the generator, because of output current. You can use a regulator made for a higher-output generator on one of lower output as long as you adjust the regulator properly. Also, alternator and generator regulators are not the same. I don't remember the specific settings for your truck, but something around 35 amps and 14.2 volts was almost a standard setting for those vehicles. Your 1-ton might have a larger generator on it, but if you don't have it loaded up with electrical accessories and lights, the 35 amps probably is enough for your setup.

Harvester

My truck has only the factory lights and no accesories.I havent fired up my truck yet,it has set for several years.When I got it it had all the wires at the regulator unhooked,not sure why so I thought id replace it.I owned this truck for a short time about 18 years ago(it ran and drove great then) and got it back about a year ago.The guy that had it put it in a barn and thats where it lived till I got it back.I just bought all new plugs ,wires,cap etc. and will soon try too fire it up.
Thanks and any more info is appreciated,
Jeremy

Unless it's rusted, or otherwise damaged internally, why not try reconnecting the one you've got? Pull the cover off and inspect the internal parts- - - -you might be pleasantly surprised at how good it is inside. Before reconnecting the wires, momentarily flash the battery wire to the one that connects to the generator armature. That will polarize the generator and get it ready to charge. Connect the wires, and start it up. If everything is working properly, the cutout relay- - -the unit right behind the battery wire, should snap closed, and the voltage at the battery terminal should go up to 13 volts or more (assuming it's a 12 volt system). The cutout relay points should spring open again when the engine shuts down to prevent the battery from discharging itself through the generator.
Jerry

I took it off the truck and found a big muddobber nest on the back, got that removed.Then took the cover off,Hotrod Lincoln you were right I was pleasantly surprised by what I found, it is very clean and shiny inside.Im gonna hook it up and try it when I fire the truck up here in a week or so.Are all these trucks positive ground?I believe I read somewhere that they are.
Thanks again for all the info you all have given me,
Jeremy

The 6-volt models were positive ground. In 1957, all major manufacturers standardized their electrical systems at 12 volt Negative ground. Your 58 should be 12V(-) unless it's been converted to an earlier system. Freightliner stayed with the positive ground until the mid-1960's. Before you hook the regulator up, rub a piece of clean business card stock or a paper file card between the points to clean them. DON"T use sandpaper or a file. The points open and close with a slight wiping action to self-clean, and any roughness at all will make them stick.
Jerry