Cruise control not working

[P505DEF]

Finally getting through the list of things wrong with my project 940

Cruise control is one of the remaining problems.

I have tested the stalk, working
I have tested the switches for clutch and brake both are working
I have tested the bellows on the throttle body and thats ok too
All looks to be connected up properly. Anyone have any ideas?

[gpl1968]

Vacuum pump or hose leak?
Diagnostics can be read after car has exceeded 35mph and still running.

[Forrest]

Definitely check for diagnostic codes. Is the speed signal wire connected at the back of the speedometer?

[P505DEF]

Originally Posted by gpl1968

Vacuum pump or hose leak?
Diagnostics can be read after car has exceeded 35mph and still running.

Cant seem to find a hose leak anywhere but going to get all the T connectors from volvo I think.

As for the diagnostics its a later car without on board diagnostics

[P505DEF]

Originally Posted by Forrest

Definitely check for diagnostic codes. Is the speed signal wire connected at the back of the speedometer?

Yea just checked its still on there

[gpl1968]

Originally Posted by P505DEF

As for the diagnostics its a later car without on board diagnostics

That's when you need one of these:

[Laird Scooby]

Originally Posted by P505DEF

Yea just checked its still on there

Two things Tom - is the speed connection on the right terminal and is the brake switch correctly adjusted? If you have a manual, add on is the clutch switch correctly adjusted!

Also a silly one - is it definitely switching on? You might move the switch on the stalk but is the cruise ECU actually registering that?

[P505DEF]

Originally Posted by gpl1968

That's when you need one of these:

Where can I get one from?

[P505DEF]

Originally Posted by Laird Scooby

Two things Tom - is the speed connection on the right terminal and is the brake switch correctly adjusted? If you have a manual, add on is the clutch switch correctly adjusted!

Also a silly one - is it definitely switching on? You might move the switch on the stalk but is the cruise ECU actually registering that?

Fair point with the switches, do you know how to check the adjustment?

As for the ecu nothing whatsoever seems to happen when I press the set switch however I know there is power to it as that has been checked. Out of all the 940s I have had this is the only one thats had cruise and I have had no experience on customers motors with it either.

[Laird Scooby]

Originally Posted by P505DEF

Where can I get one from?

Either build your own using the diagram Gavin helpfully provided or speak to Loki_the _GLT as he builds them to order.

Originally Posted by P505DEF

Fair point with the switches, do you know how to check the adjustment?

As for the ecu nothing whatsoever seems to happen when I press the set switch however I know there is power to it as that has been checked. Out of all the 940s I have had this is the only one thats had cruise and I have had no experience on customers motors with it either.

Off the top of my head, i can't remember the adjustment procedure for the switches but there is a vacuum feed to the clutch and brake switches if memory serves which is dropped when the pedals are moved (dropping the actuator/servo out) and as long as the brake lights only come on when they should (after about 1/2" of movement on the pedal), the brake switch should be ok.

Easiest way is to check the brake light operation and plug the vacuum to the brake and clutch switches so it can't drop - remember this is only to test for the unit operating as it should and to indicate where the problem lies - not a permanent solution.

Also check the earth connection for the cruise ECU and the electrical connections including earth for the servo.