cruise control

[RoyLuke]

I am troubleshooting my cruise control and so far can't isolate what is wrong. The dash switch "on" light was inop so I replaces the bulb--still inop. Does the "on' light indicate power going to the pump or is the light in parallel and not indicative of the underlying problem?
Roy

 

[DiscoBlanco]

In my experience, all the light means is that the switch is in the "on" position. It is not indicative if the system is working or not. If your light is not going on, it may be a fuse?

I had bad vacuum lines. I replaced them all and that was all I needed to fix mine.

 

[MR.T]

are you without CC completely? from my experience the throttle/cruise cable adjustment can cause a delayed setting of the CC, while a leak (small) can cause a gradual loss of speed after the CC is set.

D1 or D2?

 

[btais4595]

could be a bad brake switch.

 

[ChrismonDA]

could be a bad brake switch.

I do not believe that would be the case because when a brake switch goes bad on a disco do not know the series or year, you would not be able to change it out of gear,most of the time. I just believe the CC pump is the problem. Or like the DI vaccum hoses were the culprit drying out from the heat of the engine. Good luck how this helps.

 

[mbrummal]

I do not believe that would be the case because when a brake switch goes bad on a disco do not know the series or year, you would not be able to change it out of gear,most of the time. I just believe the CC pump is the problem. Or like the DI vaccum hoses were the culprit drying out from the heat of the engine. Good luck how this helps.

the d1 has a separate switch for the cruise control that dumps the vacuum when you hit the brake. it or the vacuum line going to it could be the problem.

 

[onewhippedpuppy]

The issue on my D1 was rotted vacuum lines and a pump plugged up with dirt, after replacing the lines and flushing the pump with water all is well. Both were pretty obvious, so I didn't have to go through any diagnostics.

If you do some searching there are multiple threads with detailed step by step diagnostics for cruise control, that might come in handy.