Cruise control on my 1990 240 isn't working. I've checked out the vacuum lines, and ran vacuum tests as/per Haynes manual. Am trying to test continuity and ran into what seems a puzzle. I pulled the instrument panel to check wire coming from speedometer. Found the wire (yellow in the 90 240). It is connected to the same connector on the back of the instrument panel that the bright headlight indicator light is connected to. This makes no sense to me and nothing in the wiring diagrams suggests that this is correct. I pulled the instrument panel out and spent an hour trying to find any other connector for the wire, suspecting that someone had had it out and reconnected the cruise control wire wrong. The cruise control wire fits on the blank connector associated with the dimmer switch light, but I can't for the life of me see why it would be connected there. Yet no other connector is available.

I checked out the connections on instrument panels of an 86 and a 93, both belonging to neighbors. Both of these are entirely different, so gave me no help. I've looked through all my Volvo manuals hoping I might find a picture. I don't want to progress any further, or for that matter, turn the cruise control on again, until I'm sure the present connections are correct.

 

I received no replies on my initial cruise control question. So far I've made no progress on my own. Let me try again.

The cruise control suddenly stopped working. I checked fuses (and actually had to replace the no. 12 fuse. Didn't fix it. Next I checked out the vacuum system as directed by the Bentley (not Haynes as I said earlier) manual. Seems ok. At that point the manual said check continuity using the wiring diagrams. That's where I got in over my head.

Is there an easy way to check to see if the cruise control switch is working? I'm thinking the problem has to be there but would like to be sure before I pull the steering wheel and air bag assembly apart.

Any ideas much appreciated.

 

Since know one else is chiming in I'll through this out their. At the base of the brake and/or clutch pedal their is a vacuum valve or pedal valve. When you step on the brake or clutch the valve opens the system to the atmosphere and cancels the cruise function. Their is also an electrical component to this switch that works as a sort of backup. These switches get used every-time you use the brake or clutch. My guess is they are defective or out of adjustment.

That would be my first stop,

Ron

 

Thanks much. I truly appreciate the suggestion. I'll look deeper there. I forgot to mention that my bulb failure light comes on each time I step on the brake. I've gone through all the bulbs and they are working. I'm assuming they are the right ones.
Maybe there's a relationship?

 

The lights from what I have read work in pairs so if the resistance of the two bulbs aren't the same (or within a certain range) the bulb out relay will make the bulb dash light come on. Mine comes at all different times, but my bulbs and lights are fine. (I have no cruise control, but it doesn't seem likely that its related.

I could be mistaken, but hopefully the case would just be the bulbs aging differently.

 

Thanks. I'll post the outcome if I make any progress.

 

The Bentley manual says that if the speedometer or the brake lights are not functioning properly the cruise control will not operate.

 

Thanks again. I'm hoping to get time to check out the brake light switch tomorrow.

 

OK, Finally traced the problem with the bulb warning light to a short in the tail gate harness. Have ordered replacements from IPD. I've gone through this before on earlier 245. Need a brain replacement to help me remember these things. However, I gobbed the short up enough with silicon to eliminate the problem of the light coming on, and the cruise control, as expected, still doesn't work. Looks like my next option is sequential replacing of parts until something works, probably starting with the switch on the stearing column. Wish I were smart enough to diagnose it some other way, but can't come up with any other approach. Thoughts?

 

Since my initial posts, I've checked out the release switch on the brake pedal (working) and tested the vacuum-driven linkage that controls the accelarater pedal (also working, best I can tell). I replaced the vacuum pump, which didn't seem to be working. Made a slight adjustment in the switch on the brake pedal. Nothing seems to help.

I find no vacuum leaks in the line. I've about run out of ideas. Any thoughts appreciated.

 

I had a cruise control issue on my 90 240 that was due to a fried chip on the odometer. In my case the speedometer & odometer still worked but the speed signal to my cruise control unit was missing so it would not engage.

The same speed signal goes to the ECU. In my case the ECU threw a 3-1-1 code. So check your codes to eliminate this possibility.

 

That sounds like a good possibility. Will check it out today. Thanks much for the reply.

 

Checked the fault codes and they gave me "no problem" readings.

 

take a look at this:
http://www.k-jet.org/files/greenbook...se_control.pdf

 

Great! and thanks. Maybe I can makes some sense of it.

 

Looking back on your older posts, you were having an issue where to connect the yellow wire to the back of the instrument cluster. It is the yellow wire that feeds the speed signal to the cruise control module. Did you ever get that wire connected properly?

 

I did get that straightened out. The wiring diagrams in the Bentley Manual confuse me greatly, though.

 

I took a look at the Green Book pdf on cruise control. While it says to use a special "tester" tool, there are other items you can check.

- Check operation of the cruise control switch
- Verify operation brake lights (I assume you have done this based on earlier posts).
- Verify that you have good vacuum running to the system. When you turn the engine off, do you hear a hissing sound coming from the center console that might indicate a faulty vacuum check valve?

If you have access an oscilloscope, you can also verify that you are getting a speed signal to the control unit. If you connect the scope to the yellow wire and spin the rear wheel, you should see pulses that are proportional to the speed you are turning the wheel.

Keep looking, I'm sure that this can be narrowed down.

 

I really appreciate all the feedback I'm getting on this. We'll be traveling over Christmas (without cruise control). When we return, I'll have several new things to check. Vacuum is one thing I haven't done.

I did an online search for the Volvo special tool for diagnosing the cc. Couldn't find it, even on ebay. Probably would have been too expensive anyway. I'm 45 miles from the nearest mechanic (who probably rarely works on Volvos) and 300 miles from the nearest Volvo dealer, so I'll just have to keep plugging along on this myself. Definitely learning a lot.

For now.... Merry Christmas everyone.

 

Finally had time to run tests on cc switch as/per the green book recommended by Bubba. Based upon instructions there, the switch checked out bad. FYI, the wire color codes didn't match up, but the numbers on the connector did. Thought I had found it. Just installed the new switch. Nope. On to testing vacuum, I guess. Sure a head-scratcher.