TOPIC: More rectifiers

I bought a radio shack #276-1185 full wave bridge rectifier today. Under $5 and much more compact than the original Merc unit. Made up a bracket and now all I lack is a couple more push-on connectors to try it out. My motor hasn't been indicating any charge since I got it. I tested the old rect. according to some info I found online. It checked out ok with an ohm meter but it looks very old and rough. I do have coils up under the flywheel and the wires coming out of them seem in good shape. However, this motor is sort of a junkyard angel and for all I know the flywheel may not be original (no markings or decals) and may not even be the one for an electric model. I'll be trying it out tomorrow to see if I get any charge.

If you buy one of these Radio Shack rectifiers, there are two wiring diagrams on the back of the plastic bag, so save the bag and don't tear it up when opening.

If this works I'll report back and include a photo of my bracket setup.

Update...The installation came out nice. Made a 3" long bracket from some 2" wide 1/8" thick flat aluminum stock leftover from another project. Mounted it to the same hole the original rectifier used. Hooked it all up, fired her up, and same results as before. No charge. I even tested right at the + and - dc terminals on the unit. I guess there's more to the problem than just the rectifier. The good news is, this being a magneto motor, it needs the battery only to start up. After that it produces its own ignition current. I don't have any accessories that need a battery. So I'll fight this battle another day.

Did you check the AC voltage between the two wires coming from the stator?

No, I did run some tests using an ohmmeter, from some posts I found in an online search, but I don't think they addressed the AC readings or procedure for checking it.

The test I found for the stator was to check for continuity between the 2 yellow wires, when they are off the rectifier. Continuity indicates OK stator.

Test between one of the wires to the stator and to ground.

Should the stator wire be disconnected from the rectifier when I do that? And I'm looking for something around 200V AC?
Thanks..

Normspeed wrote:

Should the stator wire be disconnected from the rectifier when I do that? And I'm looking for something around 200V AC?
Thanks..

Think he's talking about a static test. With both yellow stator leads disconnected, check for a grounded stator winding by placing one meter lead on either one of the stator leads, and the other to a solid ground on the block.

There should be no continuity indicated (i.e., infinite resistance); you can switch the ohms scale up to "x1000" for an accurate reading.

If you check stator AC voltage with the leads disconnected from the rectifier, be sure the meter leads are firmly attached. The high resistance of the meter provides some small load for the stator output and you don't want the leads to come off while running!

There's no specific AC voltage value that I know of, but one time when I was over at Dr. Frankenmerc's shop we were running a Merc and I observed well over 100 Volts with an "unloaded" stator! And that was at a fairly low speed.

The amount of voltage produced is only limited by the design of the stator, speed of the engine, and the load placed on the stator. Ultimately the stator is designed for a max output of around 10 amps into a battery.

If you were to place a very low-ohms resistive load on the stator, it'd generate voltage and maybe a lot more than 10 amps, but not for long, since the windings couldn't handle the current and would burn up.

If the stator isn't grounded and its popping plenty of AC output, you have either a rectifier, or wiring issue.

HTH..........ed

OK, for now I'll try the static test. As far as testing the AC output, my equipment is only an auto ranging digital VOM and I might end up grounding a wire or something and making things worse.