P38 cruise control

on my p38 v8 the cruise control isnt working. ive checked the obvious pipework etc and snipped the split ends and reconnected.

While driving along if i press the cc button on dash and press set on the steering wheel i can hear something click like a relay so im assuming it more serious than pipes.

any suggestions?

sorry if this has been asked before, i did search and found nothing like this

I think that's the way they come from the factory. My classic has been that way since I got it. When it works I rub the dash and say "thanks".

The CC system has a switch mounted on the brake pedal with a vent on it....

When you press the brake pedal this switch switches off the CC system and vents the vacuum from the CC diaphram....

If you have checked the under bonnet piping, it is possible that this switch is at fault.

Also have to tested the throttle linkage diaphram using the 'Suck Test'??

Using the pipe connected to the diaphram, suck on the end and plug it with your tongue, the throttle linkage should move and when plugged with the tongue, should stay put.....if it starts creeping back, the rubber diaphram has a leak.

There's a whole section devoted to troubleshooting the Cruise Control system in Rave. Think it's under electrical troubleshooting or something.

Mine's never worked, but it never seems to get high enough up the to do list to get any attention.

Anyone know what fuse controls the pump?

nathan5346 said:

Anyone know what fuse controls the pump?

Click to expand...

God knows. It is driven direct from Cruise ECU via pins 1 - 7 and 6. The rest of it makes as much sense as the bible.

wammers said:

God knows. It is driven direct from Cruise ECU via pins 1 - 7 and 6. The rest of it makes as much sense as the bible.

Click to expand...

Ive checked the main vacuum tube which is ok, renewed the 2 short tubes, checked the diaphram and checked the pump motor all of which are fine.

S'pose it boils down to either the cruise ecu or the steering wheel swiches

Wheres the cruise ecu?

nathan5346 said:

Wheres the cruise ecu?

Click to expand...

Right hand side of steering column behind facia.

Was going to check the steering wheel switches first, if i take the airbag fuse out will that stop the srs light coming on whilst im removing/refitting the airbag?

Don't take out the fuse...best to disconnect the battery when playing with the Airbag system....

Disconnect battery. Touch positive and negative leads to discharge system,then wait ten minutes before playing with SRS bags.

Follow the troubleshooting section on RAVE to the letter, don't be tempted to jump steps. It is very good and will pinpoint the problem cause. You will need a multimeter. Have you checked the small plastic "T" piece at the Cruise Control unit under the bonnet..they are prone to cracking. The slightest vacuum leak will render the CC inoperative.
Also be very careful removing the short walnut trim to the right of the instrument panel as it is held in place by two push in plastic studs and these can detach from the trim when trying to prise it off.

I can hear a click when operating the cruise control steering switches or dash switch on my Rangie. So, as long as you can hear it I’ll assume your switches are ok.
Be extra careful by disconnecting your airbag. I’ve changed my rotary coupler a month ago and I was expecting this bomb to explode at anytime. Scary! I recommend you follow the procedure on RAVE/Workshop manual in particular disconnect battery and then disconnect Supplementary Restraint System shorting link.

Mines fixed i took the pump assembly off, checked the pipes again and refitted. Might have been a dodgy connection to the pump.