300 Series Cruise Control doesn't work - Vacuum pipes ok

Hi All,

As above, I have a 300 series V8 with a non funtioning cruise control.
First thought was the vacuum pipes, but these all seem to be sound, with no leakage when suction is applied from an alternative source.

Is there a common electrical gremlin to look for.

I can hear a relay click when I press the Resume / Decelerate button, but nothing from the Set/Accel button.

Masterswitch lights up fine.

Suggestions gratefully received.

MW

I would say hoses as they look ok but then split at the end when fitting them back check the hose end/connection at the pump again as it is the hardest to get at. It could be the diaphragm in the actuator split or an electrical connection on the vacuum pump corroded or the pump has packed up. There's not much left.

I'm fairly certain i've elimiate the pipes.

I cut back one section, and now if i appy suction to the pump end, the system holds the vacuum fine.

Terminals of the pump seem fine.

Wondering if it is a switch problem, or the ecu, or pump itself.

Anyone know any more diagnostics, other than to start random replacements?

MW

Mike Whiskey said:

I'm fairly certain i've elimiate the pipes.

I cut back one section, and now if i appy suction to the pump end, the system holds the vacuum fine.

Terminals of the pump seem fine.

Wondering if it is a switch problem, or the ecu, or pump itself.

Anyone know any more diagnostics, other than to start random replacements?

MW

Click to expand...

Do a search!

This happened to some geezer just before the summer hols (end of june early July), clutchdust sorted it, it twas a switchy, thingy,contact bit in steering colum parts area that I can't remember the name of!

I have searched, and i think everything I found said split air pipes.

Well, I've done those and am now stuck.

I did find someone who had suggested wedging the throttle with an umbrella though......

MW

Ah i see.

Horn still works, and there is a definite relay click associated with the other button, but i guess it's possible that one of the wires is broke.

I'll take a meter to it at the weekend.

Anyone like to suggest where else (on the car) i should probe??

MW

The "dump" switches fitted on the clutch and brake pedal brackets, autos also have a neutral lockout relay located behind the drivers kick panel.

I would question the relay click u hear, as I have never heard any clicks when I use my CC.. My control switches stick our out on the right of the steering wheel column but the Haynes manual shows them located in the steering wheel so there must be two types of CC there's a bit more info in the manual on what is what in the system, but for the fault finding it's "check hoses and wiring or fuse"..

Regards

Have a look here.
I did and am now looking for a '97 300TDi auto cruise control ECU

Land Rover Cruise Control Problems - Land Rover Forums

ahebron said:

Have a look here.
I did and am now looking for a '97 300TDi auto cruise control ECU

Land Rover Cruise Control Problems - Land Rover Forums

Click to expand...

Excellent find. Thanks

Is ebay item 250189408474 any use to you?

MW

Thanks Mike I saw that yesterday. I believe it is a V8 module as I think the diesel did not get cruise control till '96 and the numbers do not match my ones AMR 5441.
Thanks
Adrian

Hi having noticed the text "the Resume / Decelerate button" I remembered I am little confused as on my 99 td5 I have not found any Decelerate button and the only way I have found to slow down is to cancel cruise by hitting the brakes.

Theres no decelerate button. Press/pull the RESume switch or touch the brakes to slow the vehicle press/pull the RES again to return to the preset speed setting.

Hi,

Problems with the cruise control are very often due to a bad amplifier. See ECU Repair Centre, Cruise control repair service and remanufactured units, Tempomat Steuergerät revision for more information, they can also repair these units.

Goodluck.

check the vacume hose is fitted on the black connector on the vacume pump

Thanks to all those owners who advised on ends of vacuum pipes cutting!!!........its worked I had 4 ends to cut
and today it worked perfectly.

Thanks again

Gordon

Dorset

Well done. It may b to late now but if u rap a few turns of pvc electrical tap around the hose at the ends before pushing them back on the ends will not split again.

Regards