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Javelin GRM+ Memberand MegaDork
9/8/22 2:27 p.m.

John Welsh
John Welsh Mod Squad
9/8/22 2:34 p.m.
Woody (Forum Supportum) said:

A Bentley enters the world of GRM. 

The Queen dies.


I was going to recommend one of these window stickers.  Now the timing might be bad (or good.)  

obsolete GRM+ Memberand HalfDork
9/8/22 2:47 p.m.

I am here for the poshness.

I am also a computer engineer who works on circuit boards in real life, so here's my 2¢ on repairing that one. If this is what it appears to be, a board with only a single layer of copper on top (and maybe one more on the back?) then the repair to the board itself is tedious but doable. The burned traces and any damaged components can be fixed. Pull parts, test them, clean up the board, fix any damaged traces with solder and some small wire if needed.

The trouble is going to be replacing that big NEC chip. From what I've been able to find, NEC D78C11G024 is a Z80 clone (8-bit CPU) with internal RAM and ROM. I don't see any memory chips on the board, so the code that makes this thing function as a seat control module is in the ROM in that NEC chip, and if it's fried, you're hosed. Even if you find an exact replacement (which I wasn't able to do in a couple minutes of looking), its ROM will be blank and your module won't work.

Maybe if you're lucky, just the driver chips (those smaller ST chips) around the CPU are fried, and the CPU is okay. Might be a long shot, but at least now you know a little more about what you're up against. Good luck!

AxeHealey GRM+ Memberand Dork
9/8/22 3:32 p.m.


I've often wondered if it would be worth ripping out the way over complicated braking system in these and just running something totally different. You know, without 14 bleed points, 2500 lbs of pressure and, I don't know, maybe one that runs brake fluid. 

I see it as finding an appropriately-sized MC and booster, front and rear calipers (unless these could be retrofitted) and maybe needling to run new lines. It would be a good amount of work but much, much easier to service and probably more reliable long-term. 

In reply to AxeHealey :

i was thinking the same thing.  Silverado 1500 or F150 would be good donors, from the booster all the way to the pads.  i wonder if the truck calipers would slip over the Bentley rotors?

Sonic UberDork
9/8/22 4:02 p.m.

I had a 69 Silver Shadow that we made into a Lemons car that shared a platform with this, except an even more complex hydraulic system in that it had a third system with a master cylinder that was there to provide some brake feel.   After lots of work on the system we got it to work pretty well and looked hard into going to a more conventional system.  

The short answer is that there is nowhere to put it.  The firewall is blocked with heaters and stuff, the rest of the valves for the system are inside the floor under the drivers feet in an amazingly complex arrangement.  

AxeHealey GRM+ Memberand Dork
9/8/22 4:19 p.m.

In reply to AngryCorvair (Forum Supporter) & Sonic :

Sonic - no space would be an issue. 

Angry - my wife's Mini uses a strange cantilever system to place the brake stuff on the right side of the car even though it's left-hand drive. Is there such thing as a remote booster in the brake world? I have to assume there's at least space for a normal MC on the firewall. 

Sorry to clog up the thread...

Toyman! GRM+ Memberand MegaDork
9/8/22 5:29 p.m.

In reply to AxeHealey :

Not clogging. Having changed overly complicated brake systems on two vehicles already, these are thoughts I've already had.

The plan for now is to get what is here working reliably, if possible. It is supposed to be a decent system if it is properly maintained. As stated, there is zero room on the firewall to mount anything. If I can't get it to be reliable then we will go to plan b. 

Edit to say. This car is going to be a driver, not a garage queen. I'm less concerned with originality than I am reliability. Whatever it takes to make it a reliable cruising machine is on the table.

DrMikeCSI New Reader
9/8/22 5:33 p.m.

I would not imagine a Z80 CPU to run the seats. Is there one for each seat?

Toyman! GRM+ Memberand MegaDork
9/8/22 5:34 p.m.

In reply to DrMikeCSI :

Of course there is. And neither one of them work. 

I'm having thoughts of building my own relay board and doing away with the memory function. I also have a couple of Arduino boards I'm not using...

DrMikeCSI New Reader
9/8/22 5:46 p.m.

Building a seat controller with the arduino from scratch would probably be easier / quicker then repairing that old circuit board. 

obsolete GRM+ Memberand HalfDork
9/8/22 5:51 p.m.

In reply to DrMikeCSI :

I agree. Based on the market research on the first page, if you built one, you could probably sell 'em for a couple hundred $ a piece.

tremm Reader
9/8/22 6:32 p.m.

"It has 14 separate bleed locations that have to be opened and shut in a specific order to properly bleed the system."

Muahahaha. I've been watching some videos of a DIY guy sort through a much rougher 1988 Rolls- https://www.youtube.com/watch?v=cbv15t7wWVs&list=PLexbWs0Wp_H4n3cu3lEC61x9lAAAgbsr7

That interior is beautiful. Glad to see it's survived in such nice condition. 

eastsideTim UltimaDork
9/8/22 6:41 p.m.

Okay, this was one of my dream cars when I was a teenager, so I'll definitely be following along.

For the brakes/suspension, if you remove the valves under the dash, is there room for a master cylinder that faces the opposite of the normal way, like on a Toyota Van?

Toyman! GRM+ Memberand MegaDork
9/8/22 7:04 p.m.

In reply to eastsideTim :

I haven't gotten that far into it. I'm not sure there are valves under the dash. They may be under the floor.

Brake diagram.

In reply to AxeHealey :

Didn't E34 BMWs have the booster mounted to the rad support, with a long rod from pedal to booster?

yupididit GRM+ Memberand PowerDork
9/8/22 7:24 p.m.

Can we get a dyno video? 

Stampie GRM+ Memberand MegaDork
9/8/22 7:39 p.m.

In reply to AngryCorvair (Forum Supporter) :

I was thinking about the pre war cars that had the MC under the floor.

Toyman! GRM+ Memberand MegaDork
9/8/22 7:43 p.m.
yupididit said:

Can we get a dyno video? 

Let's say, maybe. 

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
9/8/22 7:44 p.m.

Thanks for the closeups, I agree that board is in worse shape than I thought. Some sort of adapted module from another vehicle or a full DIY Arduinothing makes more sense.

Jesse Ransom
Jesse Ransom GRM+ Memberand UltimaDork
9/8/22 8:08 p.m.

I'm deeply Jealous. Congratulations!

Sonic UberDork
9/8/22 8:39 p.m.

In reply to eastsideTim :

The valves are under the drivers feet, not under the dash.  Not much room under the dash either, it is actually a short dash as the windshield is fairly upright. 

solfly Dork
9/8/22 9:07 p.m.

48 posts and no engine pics?

adam525i GRM+ Memberand Dork
9/8/22 10:06 p.m.
AngryCorvair (Forum Supporter) said:

In reply to AxeHealey :

Didn't E34 BMWs have the booster mounted to the rad support, with a long rod from pedal to booster?

The later V8 cars did.

XLR99 (Forum Supporter)
XLR99 (Forum Supporter) Dork
9/8/22 10:07 p.m.

This is glorious...what a beautiful car!

It appears that they gathered together all the engineers that were fired from Saab, VW and BMW for laboriously over-complicated systems, gave them unlimited adderal and espresso, and free reign to do up a braking system.   What could possibly go wrong?

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