Complex Tangled Web of Bosch 5 pin Style Relays to SSR and deeper than I thought

[Ofoo]

These small Nippondenso relays are pretty much identical to Bosch 5 pin 85, 86, 30, 87, 87a same old same old 12VDC relays, except smaller.

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Nothing unusual about them other than being the size of a quarter

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Here are their ratings

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Here are the actual components, disregard the two blue modules and switches on the right, and note there are two EDIC modules shown, one open and the other sealed/connected to the harness.

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The wiring diagram......... where the wires disappear are for power and key inputs, start/cranking, drive/running and shut off.

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A bit more detail about how it all works

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Is there a simple and easy way? I'd like to be able to use the original connector and it's metal box, even the board if possible. I'm hoping the PB editing feature will work, I did rotate, save and replace the originals so they should be less painful to see.

I know if this isn't doable solid state, I'm going to have to make a brace of bosch relays as I am not going to suffer these tiny relays and their troublesome and drty 35 year old contacts that require being un-soldered just to access and clean them.

Thanks.

 

[cowboybob]

SPDT SSRs, so long as they are "Break-Before-Make" types, could be used.

Of course, as they often require a separate supply voltage (often 5VDC), that will somewhat complicate the design alterations.

Strikes me that replacing the old relays with similar magnetic types might be simpler in the long run.

 

[Ofoo]

The old relays are ok other than having dirty contacts and I am having a hard time seeing me source 4 more of these ND's new, and soldering them in place.

As nice as it would be to keep it all in the original box and use the original connector, I'd just about have to make up a board that accommodates plug in relays. I'm not sure if mini-bosch types like that exist that can be plugged in and have the same rated capacities. Nice would be some plug in style relays, adequately rated, and with their receptacles soldered into the exact board I have, or another one that will fit in the metal case.

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One thing that pained my rusty noggin was the fact that currents flow through the various contacts both ways depending on the three simple inputs. Also I wondered about how much current leaked past the SSR's and if that would cause problems considering the motor will start to turn with very little current.

SPDT SSRs, so long as they are "Break-Before-Make" types, could be used.

Of course, as they often require a separate supply voltage (often 5VDC), that will somewhat complicate the design alterations.

Strikes me that replacing the old relays with similar magnetic types might be simpler in the long run.

 

[Ofoo]

I'm trying to decide what may be the most effective way to clean these little contact points. They have very little metal transfer showing and I don't to file what I assume is likely tungsten coated surfaces.

White cigarette paper isn't quite doing it and I'm thinking about maybe some 1000 grit wet paper followed with some contact solvent.

Any other suggestions? The coils on all of these work well and have current draw as specified, only the contacts aren't making full contact.

Does anyone know of where I may find 5 pin relays and receptacles that I could solder onto this board that will stack under 1.2" height and handle the 15 amps maximum, or at least 10... maybe 9?

My guess is this was the best that could be done afford-ably, especially considering it was for such a small run of production, in the late 70's as CMOS and stuff probably wouldn't have lasted long and would have been pretty pricey.

I recall putzing with about a 1979-80 caddy with a large and crude CMOS ecm that not much more than a sneeze would zap and render useless. Just a couple year later, all of GM's ECM's, which were pretty much cutting edge for their day having dimensioned arrays, block learn, integrators as well as somewhat useful self-diagnostic capabilities, became much more robust. I'm not sure exactly why, but, you could handle one without a ground strap and it just about always live another day.

But I digress...... it would be nice to have this circuit work as reliable as an anvil and never have to clean any contact points. I don't know how or exactly what to use.

 

[cowboybob]

If I may suggest...

There are relays out there with the dimensions you're looking for, but by adding the requirement that they be "plug-in" raises their height such that the original metal box is too small to accommodate them.

Your thought:

White cigarette paper isn't quite doing it and I'm thinking about maybe some 1000 grit wet paper followed with some contact solvent.

So, that is what I'd do. Don't worry overly about metal removal. Just try to keep both contacts as flat as possible. You can buy very high grit #, small relay contact cleaner tools (they look like miniature flat ******* files) for your final polishing.

And I would think that the relay contacts will last long enough.

It'll be a lot of exacting work, but I convinced that you'll be far more satisfied with your repair and your Benz (is it a Benz?) will be factory spec.

 

[Ofoo]

Not a Benz and I don't recall ever seeing ND stuff on any Benz's I've owned or wrenched.

It's a pre-80's Mopar, see the star on the blue module?

I'll have to say, it's one peculiar beast.

Zero luck sourcing any under 1.2" tall and I suppose if I did find some, it may make it an easier decision, especially if their pin pattern was the same.

I could likely make the box accommodate a taller stack height and still make it look original since I have more than one of these boxes and could quite conceivably tig weld two back together and never burn the ink stampings.

It just annoys me to have to think about nearly 1950's ciba dynastart clicking relay circuitry for something a pull rod currently makes happen, however bothersome that is.

Do you know of any good sites that list both physical constraints as well as ratings? Small relays and/or hockey pucks... and I've not found a single hockey puck that seemed suitable, and nothing 5 pin.

Thanks

If I may suggest...

There are relays out there with the dimensions you're looking for, but by adding the requirement that they be "plug-in" raises their height such that the original metal box is too small to accommodate them.

Your thought:



So, that is what I'd do. Don't worry overly about metal removal. Just try to keep both contacts as flat as possible. You can buy very high grit #, small relay contact cleaner tools (they look like miniature flat ******* files) for your final polishing.

And I would think that the relay contacts will last long enough.

It'll be a lot of exacting work, but I convinced that you'll be far more satisfied with your repair and your Benz (is it a Benz?) will be factory spec.