Adding Diode to OD Wiring

[Geo Hahn]

Someone (I know who but I'll take an answer from whomever is knowledgeable) had mentioned that adding a diode to the OD wiring could be a good thing. I believe the idea was to spare the ($$$) OD relay from the kickback that could occur when engaging the OD.

I think it has something to do with collasping fields or some such thing beyond me, but my question is: Am I looking at the right spot & orientation for this?

It is a positive ground car (which I think matters here):

Thanks for any advice.

 

[TR3driver]

Kerect on all counts, Geo.

My original relay lasted a long, long time without a diode; but when it finally failed, the reproduction replacement only lasted about a year (of daily driving). Then I tried a general purpose relay, which died even quicker.

After adding the diode in the early 90's, I never had another failure; and I recently moved that same cheap relay to TS13571L (along with the OD).

For negative ground, the diode needs to go with the opposite orientation; but what you show is correct for positive ground.

I also advocate adding a fuse to the supply to C1 (in your diagram). This will protect the wiring in case the diode or solenoid shorts, but more importantly it will save the solenoid if it gets mechanically bound up in some fashion (so the cutout contacts don't open). I used an 8 amp "slo-blo" (MDL-8) fuse just because that was what I had handy, but I believe an ordinary 5 amp (AGC-5) will work fine.

 

[Geo Hahn]

Thanks!

Yes, I've got the slow-blow setup in place: