Pressing Roundback Alternator Diodes - Who's done it?

If you have replaced individual roundback alternator diodes, how did you remove and install them?
Shop manual shows a 'special tool'. I used to work with guys that did this, pretty quick. I'm pretty sure they didn't have the special tool.

Somewhat related, the shop manual shows a diode tester that doesn't require cutting the leads. I'm guessing it was a transformer /DC power supply with an ammeter?? Be curious if anyone knows about what it was.

Technology has changed substantially since then. Most decent multi-meters come with a built in diode tester these days.

A diode simply allows current to pass in one direction but not the other. A tester is nothing more than a continuity tester. It should show continuity withe the leads touching in one configuration but not the opposite.

You could also perform the test by measuring for a small voltage (like a 1.5v batt) applied in different directions against the diode.

Each diode, in the case of an alternator bridge.

If using the DVOM you'll want to select the diode function for the test. The meter will "push" through the diode with a higher voltage than the ohm or continuity tests settings.

No need to remove to test, but if tests bad you'll need to isolate to identify.

Six diodes. Three positive and three negative. Wye windings connect between each pair.

If using the DVOM you'll want to select the diode function for the test. The meter will "push" through the diode with a higher voltage than the ohm or continuity tests settings.

No need to remove to test, but if tests bad you'll need to isolate to identify.

Six diodes. Three positive and three negative. Wye windings connect between each pair.

I do have a DMM with diode check. I'll look at the wiring and see if there's obvious reason why that wouldn't work for each set.

OK reading more carefuly, the FSM doesn't say to isolate each diode but to remove the connections to the stator when using the lamp test. That makes sense, since there is are three possible paths.

The special tool was read like this, which helped identify bad ones without initially isolating.

approx 1.75 amps across each is good
low on two and 0 amps on one is diode shorted.
normal on two, 1 amp on one is diode open.

i have some kind of a c clamp that i got from a mopar dealer closeout over 30 yrs ago,it is a factory tool that i was told it was to press out diodes in alternators,ive never used it,and at this late date never will

I have tested my alt diodes with the ohmeter position on my multitester, but not the value, just checking if they are open or closed and it has worked for me. Of course testing positive bank or negative bank diodes require switch the ohmeter leads to be able to check for that

That's the proper tool!



That seems to be the bottom line.
Each 3 diode rectifier can be tested that way, or with the diode setting on a DMM that has it. But it won't show which diode is bad because there are three possible paths for the test current.
That's no big deal on a squareback or any of the other manufacturers mid 70s alternators. Its much easier to just replace the rectifier.
But with the earlier individually mounted and soldered diodes, its nice to isolate the bad one.

at the risk of making a wrong post i should say im not overly proud of the c clamp if someone wants/needs it