/5 and Endura Last Diode board?

[jjwithers]

I know that /5 has a different diode board then the newer airheads (/6 /7).
Is this because of the mounts being different?

I am starting to bang my head against a wall.
I have an EnduraLast diode board on my /5 and I am wondering if it is compatible with the /5 or if i need to modify it in any way. Or go back to stock. I have two other /5 diode boards but they don't bench test properly.

I've been running around my charging system and thought I had a bad alternator (red light coming on), swapped one out and everything seemed fine (red light went off)... but now my battery is dead again (Shorai Lightweight battery).
I did a bench test in the Endura diode board and it is OK. Rotor tests OK. i have to re-test the voltage regulator. Tested for a current leak there doesn't appear to be one.
As preventative measure I am going to run ground wires from the upper diode mounts to the starter mount so there is a solid ground to the engine.

if anybody weighs in on this topic, i'd appreciate it.

-j

[Deleted User 62]

The diode boards are all the same. The difference was in the way they were mounted, early = solid, later = rubber..

[Major Softie]

Rotors can test okay static, and then fail when spinning. Veg had a brand new one that was doing that. It drove him crazy figuring it out.

[Ken in Oklahoma]

The diode boards are all the same. The difference was in the way they were mounted, early = solid, later = rubber..

I understand, rightly or wrongly, that the /5 or early boards had a lower current capacity (in line with a lower alternator output). This means that late boards will work fine in the early applications. And if you're not one to run a lot of power sucking stuff (heated bars, heated vests, lotsa lights, etc.) then you'll get along OK with early boards in late bikes.

Notwithstanding that, bigger is better.

Ken

[Deleted User 62]

"The diode boards are all the same." Refers to what is available now from BMW, one size fits all 1970 on.

[Ken in Oklahoma]

"The diode boards are all the same." Refers to what is available now from BMW, one size fits all 1970 on.

That would be the same now, of course. But I'm pretty sure it wasn't always that way. Now it would make economical sense to manufacture only the higer current board. The cost differential would be nil, whereas the inventory and stocking costs for two boards would be significantly higher.


Ken

[jjwithers]

I'm 90% sure /5 had a different diode board. 10% of me has been wrong before though....

[Kurt in S.A.]

I'm 90% sure /5 had a different diode board.

Different in what way? IIRC there were two manufacturers, Bosch and Wehrle. Some had bent-over diodes and some didn't (Wehrle). Later versions had an extra set of smaller diodes. But in general, they were the same type of unit. Now if you want to discuss Thunderchild...they were strictly aftermarket. Then there was some kind of Guzzi-style board.

Kurt in S.A.

[jjwithers]

I can't remember how they were different. But something in my head tells me that the diode board got upgraded after '73. Maybe it had to do with the mounting and such (rubber mounts vs hard mounts). But i thought the design and changed due to a larger current system vs the simple /5 electrical system.

Anyhow, i may have found my culprit. When i bought the Enduralast diode board, they talked me into their wiring as well. We'll the wiring didn't quite work out.

This little snag was hiding behind the diode board. Luckily i have many stock harnesses lying around.

[Deleted User 62]

The story I've heard is the early diode boards failed due to soldered connections letting go, but BMW thought it was a vibration issue, so they started using rubber mounts. Unfortunately, they kept failing, until they changed something with the solder joints or how they were supported. This is why the original /5 diode boards have a grey coating, but the new ones are black. Perhaps better thermal conductivity?