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As I want to narrow down what could be at fault with the cruse control I preformed this test:
Per FAQ. [John Sargent] The cruise control on 940s does not use engine vacuum but rather a vacuum pump.[Vladimir Ferdman] Apply 12V to the bottom terminal and GND to the middle and top terminals at the same time. This should activate the pump and the vacuum control valve at the same time and cause the servo at the throttle to contract. If the GND is removed from the middle, but left on the top terminal the servo should stay contracted and hold vacuum when the pump is off.
And it worked fine.
I also ran codes and got 1-1-1 all four times.
During a road test I reached down and checked the bellows (I left all the under dash stuff off so I could do this) as I switched the system on and the bellows only moved a little. It did not create a vacuum, never mind hold it and seems like the signal is getting there, but not nearly strong enough.
The wires which I could inspect in the stalk all look to be intact when I took that apart, so I still don't know what's going on.
Perhaps the computer unit is malfunctioning?
Perhaps the wires at the switch deep in the stalk are messed up somehow.
So it worked fine with a 12v direct feed, but only got a faint signal under driving conditions.
Any further testing recommended?
I do have a digital multimeter, although I wouldn't say I am really handy with it.
Thanks in advance.
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This may seem like an odd question but do you have brake lights? I haven't seen cruise control electrical diagrams for a 240 but when I lost cruise control on my 940 it turned out to be the bulb failure warning module. A bad solder joint meant that both brake lights had ceased to function so no warning and because the cruise control couldn't see the brake switch it wouldn't turn on.
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Same thing happens in a 240.
The cruise looks for a transition from 12V battery to ground when you let up on the brake pedal, so if the brake lamps do not provide the path to ground (through the bulb failure warning sensor) the cruise thinks you still have your foot on the pedal.
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Art Benstein near Baltimore
If you can smile when things go wrong, you have someone in mind to blame.
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One of the brake lights was out and I fixed it and even though all the lights are now working the warning light in the dash was staying on so I removed it. The cruise control continues to not work. Could that be related?
Do I have to have the dash warning light in the dash installed and off for the cruise to work?
I do have a couple of extra sensors, if it's those orange cans we're talking about.
Is the sensor connection covered in the FAQ?
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NO, NO, NO!
The warning light is there for a reason.
You still have an issue that the bulb failure sensor is seeing, or thinks it is seeing.
Put it back in and troubleshoot your problem.
You need to eliminate everything that you possibly can and thus far you have not.
You can do it!
Matt
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It seems that this issue is as controversial as presidential candidate politics.
Dave Barton, on his seemingly informative Volvo website says this:
The Bulb Failure Sensor (or Relay) is a device found in the 1978 and newer 240, 700, 900 that alerts the driver of a failed low-beam headlamp, parking lamp, tail lamp or brake lamp by sensing the balance of current draw between the left and right side lighting circuits. When that dash light comes on, it means the sensor recognizes that one side is drawing more current that the other. This usually means there is a bulb out, but occasionally, it can be triggered by incorrect or mismatched bulbs, or even sometimes when one side has a newer bulb than the other.
And then Dave aptly follows up with this:
#1 Recomendation: My best advice for those who are simply tired of seeing the bulb failure light come on when a bulb hasn't really failed is as follows:
Step 1: Reach under the dash and find the offending bulb in the back of the instrument cluster.
Step 2: Twist and remove.
Step 3: Take it outside and throw it as far as you can.
That's basically what I have done. He also states there he knows of no functional relationship between the sensor and the cruise control.
So my quest for a working cruise control continues. I may consult with a local automotive electronics "expert".
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I agree that the bulb failure sensor may not have anything to do with the cruise control.
I guess I should have said that you still have an issue with a light though they may all work.
I had a similar issue and finally fixed it by going through my assortment of light bulbs until I found two that pulled the same current draw when lit.
check this response from Art on how to check this circuit to determine where the problem is:
https://www.brickboard.com/RWD/volvo/1635949/220/240/260/280/step_one.html
The reason that I'm so adamant about putting the bulb back in is that in 1997 I purchased from my brother-in-law my first volvo 240, a 1989 which you see as my avatar.
unknown to me at the time, was the fact that the Check Engine Light (CEL) bulb had been removed by his mechanic because they could not get the CEL light to go off. Well after years of driving car and not knowing what I know today, the car started running really poorly. It wasn't until I took it to my mechanic and he pulled codes from OBD that we found out that the CEL light was missing.
So the moral to the story is find and fix the problems. Removing the light bulb is just a band-aid for something that is really wrong and needs addressing. Also, without the bulb there you won't know if one of your headlights is out until either you personally notice it, or a police officer pulls you over and gives your a warning or better yet a ticket for having a headlight out.
Just my 2 cents.
Matt
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Thanks for your input Matt.
I remain undecided about the bulb failure light. I have neither the skill or inclination to fuss with all the reasons it could be triggered and yes, I have been stopped by the cops for lighting anomalies. But they all seem fine now.
I also pulled the CEL, but I'll probably put that back in (after reading your story) providing the CEL agrees to be reset.
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If you can't get the CEL to reset properly as described in the FAQ, then just disconnect the battery for about 10 seconds. that will reset it for you.
Matt
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He didn't say. I ASSUMED he just couldn't get it to clear after fixing it and getting a 1-1-1 code back.
I've had this happen to me after I fix something I got the 1-1-1 code but the CEL would not go away.
unplugged the battery and all was well.
I agree with you. If he hasn't fixed the issue, the CEL will come back.
Matt
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"I may consult with a local automotive electronics "expert". "
This is only going to bear fruit if you give your "expert" some time to analyze the wiring diagrams associated with your Volvo. I have done that, so I know the bulb out sensor does indeed become "involved" with the cruise, but only if all the brake lights are out as a result of a broken solder connection within the sensor relay.
Dave's chucking advice is that of someone frustrated by mystery, and I have to agree, most owners of 240s without electrical savvy fall into this category.
It is frustrating to ask for advice, and be given conflicting information by well-meaning folk, some who have no clue what they're talking about. How do you determine who's right? Shoot for consensus? Now its time for your democracy analogy.
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Art Benstein near Baltimore
No matter how much you push the envelope, it'll still be stationery.
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Thanks for the tip on the diagrams.
As I mentioned I would do previously, today I over-rode the cruise's electronics with a ground wire at the drivers seat etc.
The cruise engaged, and the car independently accelerated. Of course that's not good. So the hit or miss investigation continue, along with democracy.
My brake lights work and I like the idea of having a bulb warning at the dash, but I don't think I have the skill to chase down every conceivable reason the warning light could be on.
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Do you have a vacuum tester? I think Mity-vac is the one sold at the auto parts chain stores?
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Art Benstein near Baltimore
Hospitality is the art of making guests feel like they're at home when you wish they were.
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Hi Art
No I don't think I need a vacuum tester as the vacuum held perfectly with the 12v applied from battery directly to the pump.
So it passed the static test (driveway with engine off) but failed the dynamic test (going up the freeway at apx 50 mph).
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"No I don't think I need a vacuum tester..."
Oh, OK. Alternative could be an old boost gauge stuck in the accessory hole teed into the cruise. You could watch it "dynamically."
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Art Benstein near Baltimore
He who laughs last thinks slowest.
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Well Art, at the risk of sounding like I have a case of oppositis, do I need a gauge to know that there is no vacuum when testing on the road. I can tell by reaching down and touching the bellows when I'm attempting to engage the cruise control when driving. The bellows is full of air.
My hunch is that is electronic. I might "install" a couple of toggles - one to the power from 12v and one to the temporary ground.
If that works then the problem is probably with the control unit, or maybe the switch.
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Well, Stanley...
I see now this is just one of several threads you've started, so you've already covered all the basics. I don't believe I've ever read any story here or elsewhere where electronics were at fault in a malfunctioning cruise. Got to be a first time, I guess. Maybe a windshield leak wound up in the controller, or like you said, the stalk switch has a broken wire or contact. Forget I suggested anything related to vacuum.
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Art Benstein near Baltimore
I dunno nothing about electronics. I'm on cruise and my head is full of vacuum.
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Could be something there Art. I just got the car a few months ago and I'm nearly sure it's a replacement windshield and did (or does) leak. I'll have to test that with buckets of water or a hose.
It has only rained here once since forever.
Any info servicing the cruise CUs? I think they cost a bunch.
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Are the vacuum valves adjusted? I take them apart clean contacts and grease the o-rings when I have problems. Pull up on the brake pedal to see if that helps.
Dan
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The vacuum valve is new, but I'll give it another look to make sure it's adjusted.
I tried the brake pedal trick. No dice, but I'll try it again.
Thanks.
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