P38A Is my mojo rising..... or do I need a new Driver Board?

[Mark Piercy]

Pull the plug for the valve block. Does the driver pack have any cracks in the silicone on the back or any dark discoloration.
I had that on a driver pack and data repaired it as there is a part that fails but any abnormality could reveal an issue?

 

[DarthDude]

Pull the plug for the valve block. Does the driver pack have any cracks in the silicone on the back or any dark discoloration.
I had that on a driver pack and data repaired it as there is a part that fails but any abnormality could reveal an issue?

That'll only tell me that there's a problem with EITHER the ECU OR the driver pack, no? Because disconnecting the valve block connector will isolate the valve block from both ECU and driver pack which is probably the same thing as disconnecting the battery.

Driver pack looks fine- at least all I see is pristine silicon (we should get Greta Thunberg on this non-repairable electronics environmental threat) but no idea what's happening under the surface. I think I'm about read to borrow a driver pack and swap it in there and see if the car behaves differently.

 

[Mark Piercy]

That'll only tell me that there's a problem with EITHER the ECU OR the driver pack, no? Because disconnecting the valve block connector will isolate the valve block from both ECU and driver pack which is probably the same thing as disconnecting the battery.

Driver pack looks fine- at least all I see is pristine silicon (we should get Greta Thunberg on this non-repairable electronics environmental threat) but no idea what's happening under the surface. I think I'm about read to borrow a driver pack and swap it in there and see if the car behaves differently.

Fair point,.
Can you get hold of an ecu as well?

 

[pwood999]

You could try this to see if the ECU is commanding the driver-pack & valves.

• Disconnect the main connector at the valve block.
• Create a new connection using only Pins 10+11 for 0V, and 12+13 for 12V.
• Battery connected, and retain the EAS Timer Relay so it wakes up every few hours.

This will allow the timer relay to provide power to the driver pack, but prevent the ECU from commanding any valves & height changes. Now if the car rises in this state, it must be the driver pack opening valves !! If the car drops then there's leaks.

Pete

 

[DarthDude]

You could try this to see if the ECU is commanding the driver-pack & valves.

• Disconnect the main connector at the valve block.
• Create a new connection using only Pins 10+11 for 0V, and 12+13 for 12V.
• Battery connected, and retain the EAS Timer Relay so it wakes up every few hours.

This will allow the timer relay to provide power to the driver pack, but prevent the ECU from commanding any valves & height changes. Now if the car rises in this state, it must be the driver pack opening valves !! If the car drops then there's leaks.

Pete

Erm... if I disconnect the valve block connector then that's the same as disconnecting the battery, no? The valve bock will be isolated from the driver pack.

But I see where you're going with this and it's a GREAT idea which I'm definitely going to do..... if I disconnect the driver pack-ECU connector (C152) and wire up 10+11 on the driver pack side direct to the battery -ve terminal and 12+13 via say a 5A fuse to the battery +ve terminal then that'll tell me if it's the driver pack is sending juice to any of the valves when it shouldn't be. Heck, I can even go to the car and turn it on and off every 6 or however many hours manually to simulate the delay relay.

BRILLIANT! Thanks for this buddy!

 

[DarthDude]

Fair point,.
Can you get hold of an ecu as well?

Actually to my dismay I just discovered that my last parts dealer crony isn't stocking P38 parts anymore so no... can't even borrow a driver pack... but there's the thing that @pwood999 said to do and I think that's definitely worth trying. Eliminate the driver pack before turning my attention to the ECU and *gulp* wiring.

Boy I sure hope it's the driver pack now.

 

[pwood999]

Turning the car off-on periodically probably won't prove much unless your rising behaviour is just after switch off. Remember, the timer relay keeps the ECU awake for a bit after switch-off. The idea above is to see if if the driver pack alone does weird stuff when the timer kicks in.

You could also setup a video camera recording continuously to see what it happens ?? But it could be a boring video to watch !!

 

[DarthDude]

Turning the car off-on periodically probably won't prove much unless your rising behaviour is just after switch off. Remember, the timer relay keeps the ECU awake for a bit after switch-off. The idea above is to see if if the driver pack alone does weird stuff when the timer kicks in.

You could also setup a video camera recording continuously to see what it happens ?? But it could be a boring video to watch !!

Well if I've rigged it up manually like that I can simulate (1) the delay relay working, (2) battery disconnected entirely and (3) delay relay failed and is supplying current constantly to the ECU and driver pack. Good note on the video too! I have an old iPhone 4s that I can use to timelapse that!

The car was riding high anyway- and I had put that down to poor calibration by the (now defunct) garage that did it the last time- until I made up my own calibration blocks recently and did the calibration myself only to find that the values set by the garage on that occasion were pretty ok (except for being as many as 8 data bits different for sensors on the same axle) and it was only after I did that, and adjusting the data bits to be within 2 of each other with a little compromising, and knowing that the height settings were ok and not wrong and therefore not to blame for the high ride height that I disconnected the battery to investigate further.

No rise.

Thinking I'd somehow solved it by merely tampering with the ride heights (why I still have these optimistic thoughts after 15 years I'll never know), I reconnected the battery and was ready to put the mystery of the high ride height to bed and was greeted the next morning with the car at wading height again.

Poop.

So I turned on the ignition, whereupon the car dropped to normal height, tried to crank the engine to find that my battery was flat (see hot start fix thread) so I removed the battery entirely and spent the next week and a half discovering that my brand new battery was nowhere near good enough for the car and looking around for a another one. During that time, at no point did the car rise although it did slowly drop to the bumpstops at the rear but as I say that was over 10 days so I'm ok with that for now.

So..... now I know it's not the programmed ride heights, and it's not (really) a mechanical leak and it's something that only happens when there's a battery connected. Usual suspect: Driver pack.

Weird.... so I post a question on a forum with knowledgeable owners and here I am! A LOT of progress and some fantastic ideas to work on. @wammers contributed the idea that it could be the ECU and now you've contributed a way to test the driver board in isolation.

I LOVE this!

Thanks guys- all of you! Keep 'em coming!

 

[pwood999]

Add a 12V light to the timer-relay output, and position in the window so the camera can see if the car rises when the timer kicks in ?