This thing is determined to not be simple. I tracked down a hz meter. Frequency increases as I run the speed up. Looks like the sensor is working, even though the r/w wire had been hooked up for months. The only thing I can figure is that it isn't connected on the other end.

Also, the speedometer and odometer works, so seemingly that system hasn't been fried.

This, apparently takes me back to a module.

 

Also, I've checked out after-market units and can't find anything made for this Volvo. I'm not sure I'm up to adapting. Certainly will be last resort.

 

if you don't have any volvo recyclers in your area, there's a giant one in Ranch Cordova (California, near Sacramento) who sells used parts pulled from wrecks.... these guys: Volvo & Saab Auto Dismantlers - New and used car parts

ignore their web catalog, just call them. they have tons of stuff thats not listed, and the cars that are listed are often out of date.

 

I located a pick and pull system and ordered it. Here's hoping.

 

Anyone without a sense of humor should never work on a Volvo cruise control. Replaced the module this morning with a pick and pull that supposedly worked. I'll assume for now it did. Numbers were right and everything installed ok. Didn't work. Not only that, the turn signals also quit. After a couple of hours looking at circuits and checking the fuses, flasher, etc., the turn signals started working again. I had done nothing to repair them. But the cc still doesn't work.

And. . . the manuals say the turn signal flasher is low on the left side of the center instrument panel. Wrong. Fortunately, the hazard lights were still working, so I could track the flasher down by sound. On this model, it is on the right side of the center dash, left of the glove compartment.

What was it Will Rogers said--'Believe nothing that you hear and only half of what you read." Or was it the other way around?

Anyhow, I seem to be down to replacing the instrument cluster with one that has a speed sensor diode known to work. Problem is the existing sensor showed an increase in frequency with increase in speed. So is it working or not?

I'm beginning to yearn for the Chevy 6 pickup i bought new in 1965.

 

relays on 240 were rather haphazardly placed, and moved around from year to year, and even sometimes within a year. it wasn't til the 740 that they got serious about centralizing them and put most all of them in a central relay panel.

first thing anyone with a 240 should do is replace ALL the fuses with new copper or brass ones, you can find these on ebay as 'mercedes w124 fuses', a complete pack of more than you'll ever need, quite cheap. the Buss brand fuses available at the local auto parts store are junk for these ceramic style euro fuses. and the tinned/aluminum fuses these cars came with just don't last that long before they start to oxidize and make bad connections. also clean the fuse contacts with a bit of emery cloth when you do this.

its highly likely your turn signals got knocked out by a corroded connection somewhere, and just futzing with the harness wiggled stuff enough to be functional again.

 

Good advice on the fuses. Guess I'm in holding pattern on the cc for a while. By all tests, it should work, but I'm obviously not getting voltage to the vacuum pump. It seems to me that the speed sensor diode should either work or not work. The frequency meter said it was working. I guess a question remains whether it was functioning at the right levels of frequency, but my local electronical engineer tells me that diodes are an all or nothing mechanism. Time to scratch my head and let the dust settle for a while, I guess.

 

I'm not sure which diodes you are referring to. However, if the frequency increases with speed when measured on the yellow wire, then I fully believe it is not an issue with the instrument cluster.

Have you tried posting over on Brickboard? I know that Art Benstein over there is very knowledgable regarding the speedometers, etc. He helped me out in diagnosing my cruise control issue.

 

Thanks. I'm told it is a diode that goes out in the instrument cluster. Anyway, speedometer, odometer, and frequency through the yellow wire all seem to work ok. The uncertainty is that at some point that nasty red/white wire that is supposed to go to a tachometer had been plugged onto the spare post on the instrument cluster. I've gone through every test in the shop manual and replaced the module. By all objective standards the cc should work. It doesn't seem to understand the facts, though.

 

If I remember correctly, it was the 740s or 940s that had issues with bad diodes in the speedometer. The 240s don't suffer that (they have their own issues).

If you are thinking of getting a replacement instrument cluster from a junkyard, try to pull one from a '89 or '90. Some of the later ones have a slightly different circuit board for the speedometer. This is due to a different tone ring added to the differential to support anti-lock brakes.

 

I appreciate the comment on the problem with the diode being 740 or 940. So far, the frequency test says the speed sensor and diode are working, although a local adviser says I need to test the diode independent of frequency. Will probably do that, but I don't see how I could be registering frequency increase with speed unless the diode is intact. But then I'm in over my head.

In spite of the fact that I've systematically ran all the tests in the shop manual for the 90 240 cc, and all circuits test out ok, I'm not getting current to the vacuum pump. I don't think I'll buy another instrument panel just yet. I need to take time to go back and study the circuit diagrams and read back through the tests. I keep thinking I'm missing something very simple and obvious.

 

One last puzzle. I checked current from the switch when the cc button is pushed. I get an instant surge of current, but then it stops. As if there is capacitance in the line that blocks it. I tested polarity in the yellow wire, reversing leads inline. Get the same phenomenon there--the instant you connect, a brief surge of power then it stops. The current increases slightly if key is on, but this "capacitance" phenomenon happens whether it is on or off. Finally, with wheels jacked up and testing yellow line I get the same instant current surge--both ways. I'm really thinking that some kind of capacitance in that speed sensor circuit is blocking continued current flow, but can't figure out why a hz meter will show increasing frequency as speed increases. I'm about down to replacing the instrument panel to get a working sensor, but, sure would like to know that is the problem. Truth is, it seems to be about all that's left.

 

For all of those who have chimed in on this thread, my thanks. I'm happy to say that, after two years of off and on fiddling, my cruise control is working. I refuse to divulge what I've spent on parts. Time is another thing. In hopes that it will help others in the future, here's the scoop, as best I can remember:

The cause was connecting the red and white wire to the second post at the back of the instrument panel. This is a trap for the unsuspecting. The wire is there, the post is there. Nothing else seems to fit. You connect it, unless you're lucky enough to find out beforehand that you shouldn't.

I got into this problem because my service light wouldn't go out. I couldn't turn it our with the button at the lower right part of the panel. Don't ask me why. As a result, I pulled the instrument panel, fiddled with the light, and put it back together. This, I'm sure, is when I plugged the B&W wire in. The cruise control quit at that point, but I had no reason to understand why.

After that, it was downhill until recently. What I went through:

Using Bentley, checking the cc as best I could. Nothing worked. I downloaded info from the web and ran a test on the switch, which suggested that the switch was bad. Nothing.

Tried various other things and finally bought a shop manual for the 1990 cc and ran all the tests there. All circuits testable worked. That left the module or. . . . the speed sensor on the instrument panel. Naturally, I replaced the module first. Nothing.

About this time I received here a notice to not plug in the R&W wire (I actually had asked a couple of locals and looked a the back of a 93--which is different. But that was after I had already done the damage).

I borrowed a hz meter and checked the speed sensor circuit for frequency against speed with the rear end of the car jacked up. Frenquency increased with speed, which suggested the sensor was working. Through all of this, the speedometer and odometer were working.

Finally, in an act of sheer frustration, I paid more megabucks for a working instrument cluster. Just put it in and the cc is working. Of course, I did not connect the R&W wire.

File this one away somewhere in case your cc stops working. Who knows what goes on in that printed circuit behind the instrument panel?

So now, on to that groan in my transmission. Torque converter?

Or is that just me groaning.

Thanks to Pierce and all others who helped.

Harley

 

this groan, is it indexed to speed or to RPM ? my first guess is, the center bearing on the driveshaft, and its rubber donut support cushion.

 

Should we start a new thread on this? I've done a lot of listening underneath, and it seems to be coming out of the transmission. I've replaced those center bearings before and will be looking at it, but I'm almost sure this is further forward.

 

yeah, probably a new thread.

if its inside the transmission, ugh, its pretty expensive to have those overhauled, and doing it yourself requires some serious tooling, and very clean work conditions. I'd suggest trying to find another AW70/AW71 transmission, most any 240/740/940 or 740 turbo has the same gearbox, except the 940 '16 valve' twincam engine uses a AW72 with different gear ratios.

 

Thanks. I'll start a new thread if I get into trouble. For now, its working and the rumble isn't too loud.