240 Intermittent Odometer AFTER Gear Replacement

cleanflametrap said:

It could be there's a whole new category of odometer failures originating in mechanical issues within the number display wheels due to debris, breakage, or previous owner monkeying. You are the pioneer in documenting it if you find the culprit.

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Do you have any experience with removing the number wheels from these later clusters? It looks like a pretty sealed unit to prevent tampering.

Never had a good reason to pull the number wheels once I learned the red gear is the one fixed to the shaft which drives the service mileage counter when the 100's digit changes. Certainly not enough experience or memory to guide someone else in effective tampering.

I wish I could give this thread a more interesting ending, but I think the fix was in fact debris removal. After taking everything apart a third time I bought a duster can and directed the air into places I couldn't get before. Sure enough, after working the gears and shaking the gauge around for a minute I pulled three very small pieces of junk out. So far its been rolling strong for about thirty miles and it's actually noticeably smoother too. Before it was very notchy where now the operation appears more fluid.

I'll report back if it starts to malfunction within the next 1000 miles or so. For now I'm going to bag up my new gears and save them for next time. Thanks everybody!

Update: A couple months ago I took the car down for body work. While I was waiting for paint to dry, I removed the cluster because this issue never officially went away.

I had an old parts cluster that I decided to start swapping parts from just to see if I could make a change out of pure chance. I found the problem before I even had a chance to take anything apart.

It was mentioned in post #9 that solder cracks are becoming pretty common. I reflowed the motor joints and they have not been an issue ever since.

Good fix. That solder is getting to be 30 years old or more.

I wish I had better news for you guys, but all these fixes haven't solved any of my problems. The cluster worked great for a month or so, but now it's back to doing its thing every day.

My first solder job was kinda ugly...


...so i tried to fix it


It's still ugly, but for some reason I still haven't replaced my gun with a normal iron. That would help a lot. I really don't think the solder is my issue though.

Considering how the odometer doesn't do anything for several miles and then works fine without any hiccups until you shut the car off, I'm led to believe that there's a capacitor that's gone bad. It has time to recharge after driving a while but discharges after the car is turned off. I dunno. This has gone over my head at this point.

Does anybody here do a refurbishing service for these clusters? I don't know why, but having a non-functional odometer is kind of a big deal to me. I just lose a lot of satisfaction in maintaining it when I don't know how far it's gone.

I did have one big win though. Cruise control hasn't worked in this car, but my girlfriend has really wanted it. I fixed that.


I don't know what this bar does, but it was bent far enough over to be touching the speed signal terminals. Cruise works now!

Knock-knock! This problem came back almost immediately after I made my last post, but I was over it at that point. There were too many other projects that required my time, and this one was a lower priority.

The symptoms haven't changed. The speedometer always works fine, and the odometer usually works just fine, but sometimes takes a few miles to start turning if the car has been sitting overnight. Oddly it almost always works as soon as I leave from work at the end of the day too. Since it got warmer outside the issue has been happening a lot less often which may be a total coincidence. I'm probably done trying to fix it unless somebody can help me perform some bench tests. I have a function generator at work I can use to simulate speed, multimeters, process meters, soldering irons, and a lot of other nifty tools at my disposal. I just don't exactly know what to do with them!

Is it worth diving deeper to fix it on my own, or should I break out the wallet for a professional rebuild?

It may not be cracked solder any longer, but a broken wire in the motor. What can happen, if the motor terminals get heated for even a tad too long, is they will melt the polystyrene of which the motor bobbin is made. Then the pin is loose and can easily break the fine motor winding wire where it attaches.

Hand soldering delicate electronics takes training and developed skills for reliability, according to any manufacturer who hires assemblers.

If you are bent on solving the trouble yourself, you could measure the motor winding for resistance while wiggling it on the board to verify the connections are sound. Check them all the way from the IC to the power delivered to the center tap, that way you won't be influencing an intermittent connection with your direct probe pressure at the motor.

cleanflametrap said:

It may not be cracked solder any longer, but a broken wire in the motor. What can happen, if the motor terminals get heated for even a tad too long, is they will melt the polystyrene of which the motor bobbin is made. Then the pin is loose and can easily break the fine motor winding wire where it attaches.

Hand soldering delicate electronics takes training and developed skills for reliability, according to any manufacturer who hires assemblers.

If you are bent on solving the trouble yourself, you could measure the motor winding for resistance while wiggling it on the board to verify the connections are sound. Check them all the way from the IC to the power delivered to the center tap, that way you won't be influencing an intermittent connection with your direct probe pressure at the motor.

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Oh I'm not bent over it anymore. If it is truly beyond me then I'm okay with sending it to the right guy. I'm just really curious about what it could be. That's interesting, but if it's that delicate I don't want to make it worse!

volvowagoon said:

Oh I'm not bent over it anymore. If it is truly beyond me then I'm okay with sending it to the right guy. I'm just really curious about what it could be. That's interesting, but if it's that delicate I don't want to make it worse!

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If you send it somewhere, how will you drive the car meanwhile? I'd be happy to try without messing with your wallet, as intermittent troubles are the most challenging and the best learning experiences, but I can't promise professional turnaround time. benstein at cleanflametrap dot com

cleanflametrap said:

If you send it somewhere, how will you drive the car meanwhile? I'd be happy to try without messing with your wallet, as intermittent troubles are the most challenging and the best learning experiences, but I can't promise professional turnaround time. benstein at cleanflametrap dot com

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Haha I appreciate the concern! I'm not sure if I'm ready to go too deep into it at the moment. I have a spare car, that might be up and running as soon as I get it tuned. Maybe then I'll be able to look into this a little further. I guess the point of the update was more or less an attempt to formulate a game plan that I'll execute later.

The never ending odometer repair continues. I did try something different this time though. Maybe you'll think I'm crazy, but I think my theory is solid.

Let's recap... It's a pun. You'll see. The odometer worked almost all summer as far as I had noticed. However, it reappeared on the first cold morning drive of fall. Weird. Or is it?! I have already reflowed most of the joints, so I don't think it's an expansion/contraction issue. What components do we all know degrade in the heat but don't show symptoms until it's cold out? Batteries. Which smaller components in a circuit board are nearly the same thing as batteries? Capacitors!

To be honest, I didn't even know if the odometer board had one until I pulled the cluster apart. I just had a strong hunch. Sure enough, there it was. It's even blown out and nasty. The specs are no longer legible, but I was able to find a picture in Dave Barton's gear replacement guide. It's a 47uF 16V just like the others.


Desoldered


New one in place. There's a "+" printed on the board. Don't reverse the polarity!


Soldered


Wiggled the leads until they broke. Snips work too.


My new cap has a higher voltage rating and sits a bit taller, but it still fits with everything back together.


I won't know for sure if this did the trick, but I think it certainly needed to be done anyway. It's pretty cold here today as well, and I managed to get the repair done before it warmed up. The odometer was spinning the moment I started moving! Let's hope it continues to do so through the winter. After that, I'll be able to call this "fixed" once and for all.

That's a good find! The caps are a known issue with the clocks. Here's to hoping it behaves itself now.

volvowagoon said:

...
Let's recap...
I won't know for sure if this did the trick, but I think it certainly needed to be done anyway. ....

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I'll guess if it does "do the trick" the fault you correct will be part of the removal/reinstallation disturbance, not the capacitor replacement. I know for a fact the speedometer and odometer will work without interruption without those two electrolytic caps even present. You could try it. However, in the rare circumstance that one has an intermittent internal short circuit, a cap replacement could be the fix for your symptoms.

cleanflametrap said:

I'll guess if it does "do the trick" the fault you correct will be part of the removal/reinstallation disturbance, not the capacitor replacement. I know for a fact the speedometer and odometer will work without interruption without those two electrolytic caps even present. You could try it. However, in the rare circumstance that one has an intermittent internal short circuit, a cap replacement could be the fix for your symptoms.

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Dang. It was kind of a shot in the dark. I suppose it's still possible, but seems really unlikely given what you just told me. We'll see. It spun all weekend, but we have a cold front coming in tomorrow. If it acts up, I'll semi-expect it to happen on Wednesday.

I'm in the same boat here. I've replaced gears, cleaned out teeth, blown out what i couldn't find, and reflowed the solder on the motor. My speedometer always works, but my odometer doesnt work until 5-10 miles into 23 mile commute. This must have started recently, because I track my mileage pretty closely, and i would have seen that much. Last time I had the cluster out, I noticed that the motor spindle felt a little sticky. I cleaned it off, it spun freely, and the odometer worked again.. for a day. I'll keep fiddling too.

MochaBear said:

I'm in the same boat here. I've replaced gears, cleaned out teeth, blown out what i couldn't find, and reflowed the solder on the motor. My speedometer always works, but my odometer doesnt work until 5-10 miles into 23 mile commute. This must have started recently, because I track my mileage pretty closely, and i would have seen that much. Last time I had the cluster out, I noticed that the motor spindle felt a little sticky. I cleaned it off, it spun freely, and the odometer worked again.. for a day. I'll keep fiddling too.

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I hope to hear your fix if you find one. The wagon is my fiance's daily, so I can't watch it close enough to know if it's working correctly. My updates are very far apart because of this.

volvowagoon said:

I hope to hear your fix if you find one. The wagon is my fiance's daily, so I can't watch it close enough to know if it's working correctly. My updates are very far apart because of this.

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I just hope i can find one to post. I had it our again this morning. Upon disassembly, i think the commutator was stuck this time. I think. I poked with a pick, and only the first poke felt stuck, i was unable to find any notchiness thereafter, or teeth, or leftover shmug making the motor sticky. I blew it out again, very aggressively, this time. I spun the gears with air, exactly the way you're not supposed to with bearings. I also tightened the tangs on the 4 box connectors to ensure good contact and bent the prongs on the triple connector for the same, cleaning that contact with electrical cleaner. Before final assembly, i wiggled each of the numbers with a nylon trim clip without the car moving. Worked perfectly back and forth from work today, but I can't be sure of anything yet. I'll post an update again when I know more.