My '93 940 turbo's cruise control stopped working and I hope some one might have a clue to what's wrong? It worked fine since I've owned the car(abt 3 months) but abruptly stopped about a week ago. I don't know if this is related or just coincidence but I went to bigger diameter tires in the back as an experiment to see if I could get better mileage. But I didn't realize that different size tires between front and back would confuse the ABS computer. The light came on so I switched back to the same size and everything's fine as far as that goes, light's out and the system works. But during this time the cc stopped working. So I went to brickboards and did all the tests I could; no blown fuses, brake lights all work, bulb out relay works, the system holds vacuum, the vacuum pump works when hotwired, the brake switch holds vacuum when pushed in and releases when released outward, the controller has 12v going to pin 11 and there's continuity between pins 11 and 6. Don't know what else I could check? Oh, and no diagnostic codes from Box B, pin 2. Also, I did the individual component tests using the diagnostic light and all we're perfect. My last guess is that the speedo(which works fine) is not sending a signal to the cc control unit. Does anyone know how to test that?

 

Gee, the only thing left is the switch and the CC "brain" which I've never seen go bad...

 

The switch was tested during the component diagnosis and it passed. I did run across this wiring diagram that shows the ABS system wired into the CC control unit, so back to my hunch that I may have fried it when messing around with tires sizes. Yet it did pass the brickboard tests. I think I might be chasing my tail unless I can check if the speedo is sending anything to the control unit. Any idea about that?


http://www.volvowiringdiagrams.com/v...940%201994.pdf

 

When my '90 240 has inoperative cruise control, I just switched speedometers out to fix it and double checked the wiring.

Swap parts, or just get a Toyota.

 

Great advice! Do you work for the government?

 

Problem solved. I pulled the hose going to the brake switch and plugged where it connected to the T fitting off the pump. Went for a drive and it worked perfectly. Even though I did a vacuum test it turns out the brake switch had a slow leak. It didn't show up when I drew vacuum but when running I guess the vacuum pump pulls a lot more. I guess this is another wear item since every time the brakes are used the switch is moving, and it's all plastic. Anyways, thanks for responding.

 

Come on now...if he worked for the government he'd give you a GM and make me pay for it.

 

but it would be a really crummy Aveo, stripped base model.

 

If I worked for the government there would've never been a Cash 4 Clunkers program! And you'd all have Fords.

Heck, maybe I'd find a way to make vintage cars a bit cheaper to keep going, just as long as they're in decent shape though, I ain't rewarding tasteless mods.

 

Toyotas? Fords? I think you're on the wrong forum.

 

Yeah, OK, we all hate the government but then we vote the same back in time after time. "Every people has the government it deserves!"

Back on topic of cruise controls and Volvos:
The one big problem in all these cases, trying to help diagnose issues based on the poster's statements. Owner says they checked this, replaced that, and you have to assume that the check and the replacement were done correctly, if not, all bets are off.

 

And sometimes the advice has short comings, just like the testing. In my case, if Brickboards had said to make sure to hold vacuum for 15 seconds the problem would have been discovered the first time. But, it still beats paying a shop $100/hr.