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1987 Volvo 240 Cruise Control intermittant

everyhumanvovo

everyhumanvovo

Member
Joined
May 4, 2009
Location
chill'n@Yuper Mickigan, prior Oregone, USA
Have an 87 240 manual which if I recall when installed in 2010 had a slightly different cruise setup than other years of its vintage. It has been rather intermittant in function last couple of years. Some days it will set a speed, some not. Sometimes it lets go of set speed. Finally, hasn't worked at all for a couple months.

Had installed with NOS switch/stalk, and rest of system was used parts. It worked well for a few years. Started couple years ago with some days it worked, some not at all. Or, some days it would start working after several re-starts/attempts. Normally, if it did start working, it worked for rest of day, mostly.

Likely, not stalk switch as that is least used. Thinking may be vacuum issue, but I think hoses look alright. Does not seem related to environmental conditions; possibly works less often in hot weather. Two months back, it didn't work on 90 mile trip at all with about 50 attempts to set the speed, but, then worked all the way back without issue. Any insights much appreciated!
 
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I just scanned an installation manual for 240-1991....so a vacuum pump, brake/clutch pedal vacuum switches, brake electrical switch, and a vacuum servo motor are used.

For these mechanical-electrical parts, brake/clutch vacuum switches do fail....if vehicle is a manual, there are two vacuum switches, one on the brake pedal, and one on the clutch pedal. These could be removed, and bench tested.

Myself, I'd rig up a vacuum gauge via T-fitting, and see if vacuum exists.

Hence, either your vacuum pump, or brake/clutch vacuum switches may be the issue.

If brake light was on, this sends 12volts to cruise control module via brake/clutch vacuum switches. So, either a lack of vacuum kills cruise, and if 12volts via brake switch is sent to control module.

On older vehicles, vacuum switches (brake/clutch) were known to fail with time.

Tracing circuits from Vehicle Speed Sensor to Cruise Module can be done, but I suspect a failed vacuum switch(es), or vacuum pump would be a good starting point.
 
84B23F said:
Servicing the Cruise Control on my 1985 Volvo 240

https://www.youtube.com/watch?v=K3qPGJH9gbA
Click to expand...

Thank you very much. I think it may be a failing vacuum pump which would seem to explain its intermittant functioning. Clutch and brake pedal switches may be culprit, but haven't noticed any thing linking them except those switches are part of the cruise setup. Will do a vacuum test!
 
everyhumanvovo said:
Clutch and brake pedal switches may be culprit,
Click to expand...

Later model Volvos used a different setup than yours. Video shows how to test brake/clutch vacuum switches.

1985 - If electrical plugs are removed from brake/clutch switches, this will rule out an electrical switch issue. Fuse #6 powers up this circuit, so fuse must be good.

1985 - Has a retardation switch, which allows for cruise on, or shuts it off. See this pic, and click on it for a larger pic.

A vacuum switch, or an electrical switch can fail...clutch/brake switches would be high on list to fail.
 
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