P38A Cruise Control repair....I hate this Ba$tard thing. ;-)

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DanClarke

DanClarke

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Today was the day. Not raining, not baking hot either.
I want to replace all the rubber vacuum hose elements on the Cruise control for some nice silicon hose that I have purchased. I have a reasonable idea of the routing on the engine-bay side of the bulkhead, but after removing the panels etc. under the steering and assorted stuff I cannot find the vac-hose or where it attaches to what on the cabin-side of the bulkhead. Needs 2 people really one wiggling the existing cable, the other finding the bit wot is wiggling.

Is there a guide anywhere for this as a pictorial for the dull-witted bumble-klutz like me?

All help/suggestions gratefully received. TIA.
**UPDATE** It's OK I found the little bugger. Silly me. ;-)
 
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OK, all vacuum hose replaced for nice new 6mm Silly-cone hose.
When I press set when over 30mph I hear a click from under the dash, and when I press cancel/resume I get a similar click, but no cruise operation.
I have had a look at the ETG for cruise and it seems its not going to be easy to fault-find while travelling at >30MPH (a starting condition input from the BeCM.
I will look for some how-to's on U-toob.
 
DanClarke said:
Today was the day. Not raining, not baking hot either.
I want to replace all the rubber vacuum hose elements on the Cruise control for some nice silicon hose that I have purchased. I have a reasonable idea of the routing on the engine-bay side of the bulkhead, but after removing the panels etc. under the steering and assorted stuff I cannot find the vac-hose or where it attaches to what on the cabin-side of the bulkhead. Needs 2 people really one wiggling the existing cable, the other finding the bit wot is wiggling.

Is there a guide anywhere for this as a pictorial for the dull-witted bumble-klutz like me?

All help/suggestions gratefully received. TIA.
**UPDATE** It's OK I found the little bugger. Silly me. ;-)
Click to expand...
Yep, the EAS is locked when the brakes are on.
 
Round TWO
I connected up my trusty Nanocom to see if it could tell me anything about faults in the Cruise Control.
Unfortunately, it responds with "Unable to communicate with ECU" for each and every option you select.
The system lights the Cruise Button on the master switch on the dashboard.
When I drive and press the "Set" button, I hear a relay click (dump valve?) and also when I say resume/cancel.
So, presumably something is driving that relay/valve. No vacuum pump running though (as far as I can tell).
Dead ECU comms circuit only? or something else?
Puzzled I am indeed. I shall work my way through the ETG for cruise control eventually. But if anyone has a brilliant idea, I would love to hear it.
 
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Go to my Dropbox link in the tech section and there's a writeup of how to test the vacuum pump there. At least you know then that it can physically operate the throttle
 
After much shuffling from foot to foot and sucking of teeth I followed the ETG on Cruise Control.
It suggests at Step 3B that my Convertor/Inverter Module is duff. One is on order. We will see.
 
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Have you checked the bellows are actually holding a vacuum?
My cruise doesn't work but that's because the vacuum switch on the brake pedal doesn't stay clipped in place. If i can cure that, it will work again
 
kermit_rr said:
Have you checked the bellows are actually holding a vacuum?
My cruise doesn't work but that's because the vacuum switch on the brake pedal doesn't stay clipped in place. If i can cure that, it will work again
Click to expand...
It all used to work but suffered from Psycho-road-killer speed increases when under cruise control. Then the stealer tried to fix it and broke it completely so I had no cruise operation at all.
I found split hoses (now all replaced end to end with 6mm Silicone hose) and the light lights, the valve clicks under the dash but no cruise control. The ETG has been followed to the letter and all checks so far are OK up until step 3B. A failure at this step says that this points to a faulty Converter/Inverter module; so I will replace it. I can put volts/earth on the pin of the vac-pump and see if it runs, while I am waiting :)
 
Fingers crossed for you! I've tried to buy a new switch but they're not available!! And i can't figure out how to secure it.. as it stands, the system thinks the brake pedal is permanently on
 
kermit_rr said:
Typical! Which parts are shared?
Click to expand...
It was the XYZ switch for the ZF auto gearbox, but I am in error, its not that they are shared, its that there are 2 of them you can find, each is for the ZF 4-Speed gearbox, but one costs nearly twice as much as the other.
Looks like the plugs are different and that's all. For £200 I would get my soldering iron and heat-shrink out. ;-)
upload_2019-9-13_20-10-35.png
upload_2019-9-13_20-14-59.png
 
Oh, and while I was going through the ETG for the Cruise Control it dawned on me that I had been a dumbass when trying my NANOCOM.
The Cruise needs to be "switched on" on the dash, and the Ignition in Position 2 and the gear selector in a forward gear in order for the conditions to be met for turning the ECU on.
So I tried again this evening and sure enough I can talk to the ECU and see it detect the status of the Set/Res switches on the steering wheel so maybe the ECU wasn't duff (means I now have a spare).
When the replacement Converter/Inverter arrives I can cross that off the list too if it doesn't fix it (and maybe I'll have another spare). Cheap to buy though.
If I'm reading the ETG right, there is a process to hot-wire the cruise-control ECU plug to cause the Vacuum pump to spring into life, so that's another test yet to come. But let's follow the guide step-by-step.
 
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DanClarke said:
Oh, and while I was going through the ETG for the Cruise Control it dawned on me that I had been a dumbass when trying my NANOCOM.
The Cruise needs to be "switched on" on the dash, and the Ignition in Position 2 and the gear selector in a forward gear in order for the conditions to be met for turning the ECU on.
So I tried again this evening and sure enough I can talk to the ECU and see it detect the status of the Set/Res switches on the steering wheel so maybe the ECU wasn't duff (means I now have a spare).
When the replacement Converter/Inverter arrives I can cross that off the list too if it doesn't fix it (and maybe I'll have another spare). Cheap to buy though.
If I'm reading the ETG right, there is a process to hot-wire the cruise-control ECU plug to cause the Vacuum pump to spring into life, so that's another test yet to come. But let's follow the guide step-by-step.
Click to expand...
Test procedure for pump/bellows/release valve in my Dropbox in těch archive
 
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