Tecumseh Charging System

The 3 amp charging system used on many of the H and V series engines is composed of a center tapped alternator which produces 24~35 volts AC depending on engine rpm. Full wave rectification is achieved by grounding the center tap and using diodes on either side of the center tap thus producing 12~18 volts on either side of the center tap (ground). The B+ output of these diodes PN# 30842/36909 are parallel connected to a 6 amp fuse which connects directly to the positive battery lead. The system has NO regulation. A little more background on the diodes used in the system, they are actually 1N1081 fuse holder type diodes rated at .5 amp forward current which means that there is no way possible for this system to charge at the rated 3 amps. Couple the low current capability of the diodes with the 6 amp fuse and suddenly the rectifier becomes the fuse! In the case of the H-60 on my 654 the PO decided on a 25 amp fuse, a bad call resulting in 2 blown diodes. A good diode should have continuity in one direction and not the other.

H-60 rectifier/fuse panel



In the event you need to replace your diodes, check for the correct value fuse and do a search for 1N1081 diodes (1N1081 through 1N1084 are compatible, the higher numbers having a higher peak voltage rating) which can still be found and are much cheaper than the Tecumseh part number.

Very nice! :goodjob

So with a steady hand, correct diodes and a soldering iron....

You can replace those god awful expensive fuse type diodes with a couple 75 cent diodes..

AJ WH Ranger wrote: So with a steady hand, correct diodes and a soldering iron....

You can replace those god awful expensive fuse type diodes with a couple 75 cent diodes..

You got it AJ, I silver soldered in a couple of these... HER602, 6 amp


Even a 1N4001 1 amp would be an improvement.

Yes Nailed it!

The only difference with those is the VF (forward voltage) which is just slightly under the original 1.5v coming in at 1.2v.

[strike]But on something like this.. That .3v will not be missed at all as long as the engine maintains at 6 amp. Because the VF (I believe) will decrease with a drop in current[/strike]..

Edit...

I was completely on the wrong semiconductor... Forget what I said.. I will leave it up so people can read my mistake...

A diodes VF (forward voltage) is it switching on voltage... Nothing what like what I said below... Which also brings up another point Major. If the IF is not at the rated 6 amps, what will the VF actually be at? I doubt it follows a linear path as most diodes don't.

AJ WH Ranger wrote: Yes Nailed it!

The only difference with those is the VF (forward voltage) which is just slightly under the original 1.5v coming in at 1.2v.

[strike]But on something like this.. That .3v will not be missed at all as long as the engine maintains at 6 amp. Because the VF (I believe) will decrease with a drop in current[/strike]..

Edit...

I was completely on the wrong semiconductor... Forget what I said.. I will leave it up so people can read my mistake...

A diodes VF (forward voltage) is it switching on voltage... Nothing what like what I said below... Which also brings up another point Major. If the IF is not at the rated 6 amps, what will the VF actually be at? I doubt it follows a linear path as most diodes don't.

AJ, according to the HER602 graph, at 3 amps (alternator output max) the Vf is .8 increasing to 1.0 at the rated 6 amp max.