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Old 08-17-2019, 12:06 PM   #1
volvowagoon
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Default Intermittent Odometer AFTER Gear Replacement

I'm probably going to get my head chewed off if I don't mention that I DID read https://www.240turbo.com/240-odometer-repair.html before coming here. However, I'm two for two on having odd odometer repair experiences.

The speedometer on this car ('89 245) has always worked just fine, but lately I've noticed that it sometimes takes about ten miles for the odometer to start working. I figured, it wasn't a huge deal. I'll buy the gears and replace them when they come in. That wasn't the issue. The gears I pulled out were still in good shape. I figured I would try the new ones anyway in case something was stripped that I couldn't see. My eyes aren't the greatest.

The odometer came to life right away, but gave out after about ten miles. I have a parts cluster, but it's for a non-cruise control car and the car I'm working on has working cruise that we would like to retain. Has anybody in here had luck replacing individual components on their speedometer circuit boards? Is it possible that the little capacitor on there is giving me trouble?

If anybody by chance has a good K9800 with cruise control speedo circuit board I would gladly buy it from you! Thanks!
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Old 08-17-2019, 01:46 PM   #2
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AFAIK, the electronic speedometers are the same cruise versus non-cruise.

Cruise control uses a separate control box and connects to the VSS Vehicle Speed Signal from the back of the speedometer. On a '89, I think it's a single blue wire with a spade connector on the cluster PCB, next to the speedo. It's pretty easy to swap speedos if the cluster is out of the car.

For the intermittent odo, maybe the gear drive shaft is slipping? I know the early mechanical (k-jet) speedo had this problem.
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Old 08-17-2019, 05:07 PM   #3
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Originally Posted by bobxyz View Post
AFAIK, the electronic speedometers are the same cruise versus non-cruise.

Cruise control uses a separate control box and connects to the VSS Vehicle Speed Signal from the back of the speedometer. On a '89, I think it's a single blue wire with a spade connector on the cluster PCB, next to the speedo. It's pretty easy to swap speedos if the cluster is out of the car.

For the intermittent odo, maybe the gear drive shaft is slipping? I know the early mechanical (k-jet) speedo had this problem.
Thanks for the info. I'm really wanting to keep this assembly if possible because I'd like the keep the mileage pretty accurate and my parts cluster is almost 50k off. The slippage is a solid thought though. The gears seemed to slip on and off pretty easily! Maybe I'll try a dab of super glue on the drive gear to the shaft.
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Old 08-17-2019, 06:08 PM   #4
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I didn’t entirely read your post, but I had a very similar experience and everyone’s suggestion was to check for leftover gear pieces, which I did. There were none.

My solution was to reflow some solder joints as per Arts write up on cleanflametrap.com. After reflowing maybe 3 or 4 joints, I’ve had 100% odometer reliability.
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Old 08-18-2019, 02:23 PM   #5
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Originally Posted by iHateVolvoPeople View Post
I didnít entirely read your post, but I had a very similar experience and everyoneís suggestion was to check for leftover gear pieces, which I did. There were none.

My solution was to reflow some solder joints as per Arts write up on cleanflametrap.com. After reflowing maybe 3 or 4 joints, Iíve had 100% odometer reliability.
Yeah, I just got back in my cluster. After looking further into how it all works I can see that super glue would have been a destructive move. I'll try re-flowing since the cluster is out again, and It don't have any other ideas yet.
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Old 08-18-2019, 02:25 PM   #6
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Quote:
Originally Posted by bobxyz View Post
AFAIK, the electronic speedometers are the same cruise versus non-cruise.

Cruise control uses a separate control box and connects to the VSS Vehicle Speed Signal from the back of the speedometer. On a '89, I think it's a single blue wire with a spade connector on the cluster PCB, next to the speedo. It's pretty easy to swap speedos if the cluster is out of the car.

For the intermittent odo, maybe the gear drive shaft is slipping? I know the early mechanical (k-jet) speedo had this problem.
I misunderstood what you meant about the gear drive. That's possible too although I have no idea how to check that. I would think it would start and recatch around the same number if that was the case, but it's hard to say.
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Old 08-18-2019, 07:30 PM   #7
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Quote:
Originally Posted by volvowagoon View Post
I misunderstood what you meant about the gear drive. That's possible too although I have no idea how to check that. I would think it would start and recatch around the same number if that was the case, but it's hard to say.
The electronic speedometer does not have a shaft-slipping issue with the odometer. My canned response to failed gear replacements:

1. Find the broken teeth and get them out of the ring gear.
2. Be sure the rotor's thrust bearing is not jammed.
3. Reflow the three motor pin terminal solder connections.
4. Check to see you didn't plug the tach wire on the cruise control tabs.
5. Read this thread 92 240 Speedo good, odometer inoperative
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Old 08-19-2019, 06:04 PM   #8
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Thanks for chiming in. I hoped you would! I will triple check for broken teeth, but I haven't noticed any the first two times I was in there. My old (appear to be original) gears still looked good too. I tried compressed air and didn't notice anything flying out.

The rotor's rust bearing? hmm I'll don't recall seeing anything like that, but I'm sure I can find it because the description is pretty self explanatory. Since I know my parts cluster has a good odometer I might use that for reference too.

Thanks again!
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Old 08-20-2019, 10:59 AM   #9
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Because yours is intermittent, I suspect either (1) or (3) in the list.

(1) I'm a little at odds with Dave Barton's treatise. As pertains to your project, I refer to the advice to use compressed air to find the broken teeth, which, if you didn't find them on the mushy gear are certainly left behind. Usually they are in the clear cast ring gear, but the point is, using a blast of air will mean you'll never be certain they are removed. Also, depending on just how clean your work area and air supply are, you may introduce iron filings, etc. to the speed meter portion in the small air gap between the moving coil and the magnet.



But you say:

Quote:
My old (appear to be original) gears still looked good too.
If the old gear has all its teeth, you don't need to search for any more!

Other issues exist too, like the brown red wires being attributed to cruise. They are for the service reminder light. bobxyz is correct, the clusters are not cruise-specific.

The 25-tooth gear vs 26-tooth gear creating mileage errors? No. The gear you are replacing is an idler gear in the planetary gear train. The gear ratio is adjusted by the number of teeth in the stationary casting (61 in a US wagon, 63 in a US sedan) where your broken teeth probably lodged. The number of teeth in the broken gear correspond to its diameter which must fill the distance properly between the drive and the ring and maintain the gear pitch chosen for them.


(3) The cracks around the motor solder pins are a little more common than "a few others" because the motor's weight is supported by those pins being soldered, and once you remove the two frame screws, that's all that's keeping it on the board. The solder has become brittle over the years, and if you have any history with all the electronic relays in this car, you know the solder cracks around the heavy parts. And now you're handling it.



This reflow being recommended often divides the failures from successes because care must be taken to keep from loosening the motor pins in the plastic bobbin or damaging the motor winding termination on them. That means reflowing the joint quickly - say one second - with just a touch of new resin flux core solder. These joints are tin/lead solder, not the stuff you can buy today at Walmart.



The thrust bearing is easy to check with a small pick, but when it is jammed the odometer fails to move at all, not just sometimes, once the screws are tightened. The technique is to see that the magnetic odometer motor's rotor can turn freely taking into account the magnetic resistance to the motor poles. I don't think that's your issue.

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Old 08-20-2019, 07:23 PM   #10
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Interesting! I have the cluster apart again, and I thought I had it figured out, but I was wrong, because I'm actually feeling it hanging up mechanically without even having the board in place. Like so....



I spun it by hand for about 4 miles before I felt it suddenly get tight. I guess this rules out an electrical issue and explains why my cluster smells funky when I pull it out.

SIDE NOTE: Before inspecting the clear teeth for missing teeth (looks good) and the thrust bearing (looks/feels good) I noticed that the thrust bearing could interfere with the planetary gear if it was compressed enough. This shouldn't be my issue at hand since I don't think it gets sprung that far with the motor housing on; however, I flipped the gear right side up. I thought this was how it came apart, but I should have noticed the limited tooth engagement.



Anyway, the assembly is locked up. I'm going to have to keep looking for debris I guess. Perhaps it is just the big gear that is original? There could still be a piece in there.


Last edited by volvowagoon; 08-21-2019 at 07:17 AM..
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Old 08-20-2019, 07:41 PM   #11
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My next test was to pull the gears out again and spin each mechanism (odo and trip) by hand. They are smooth as silk until I roll it back to where it was and put the gears back in. It locks up in the same place. I tried putting the old gears back in since they seemed to work okay, but it does the same thing. I can't get a good picture, but there really doesn't seem to be anything in the way that would jam up the gear teeth.... strange.
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Old 08-20-2019, 07:52 PM   #12
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Quote:
Originally Posted by volvowagoon View Post
My next test was to pull the gears out again and spin each mechanism (odo and trip) by hand. They are smooth as silk until I roll it back to where it was and put the gears back in. It locks up in the same place. I tried putting the old gears back in since they seemed to work okay, but it does the same thing. I can't get a good picture, but there really doesn't seem to be anything in the way that would jam up the gear teeth.... strange.
Did you already reflow the 3 solder points?
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Old 08-20-2019, 07:58 PM   #13
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I redid the ones for the two wires coming in, but I'm not bothering with anymore since I have a mechanical hang up.
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Old 08-20-2019, 08:12 PM   #14
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Quote:
Originally Posted by volvowagoon View Post
I redid the ones for the two wires coming in, but I'm not bothering with anymore since I have a mechanical hang up.
Iím a little bit confused about how itís binding up? IIRC, theyíre not supposed to be able to move backwards so people donít roll odometers back, I could be wrong though.
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Old 08-20-2019, 08:18 PM   #15
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It binds up when rolling the correct direction. It will roll backward fine, but then gets hung up in the same spot when I roll it forward again. I didn't try to make it hang up backwards.
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Old 08-20-2019, 08:56 PM   #16
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It binds up when rolling the correct direction. It will roll backward fine, but then gets hung up in the same spot when I roll it forward again. I didn't try to make it hang up backwards.
If you remove the motor, does it itself spin freely?
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Old 08-21-2019, 07:21 AM   #17
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Do you mean the armature or the housing? I'm not physically touching the actual numbers. I'm just spinning the armature of the motor like you see in the first pic of post #10. If you take the armature out the gears will not stay meshed which makes it hard to spin.
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Old 08-21-2019, 09:21 AM   #18
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Quote:
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You have the little gear wheel in facing the wrong way. Flip it and check.
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Old 08-21-2019, 09:29 AM   #19
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You have the little gear wheel in facing the wrong way. Flip it and check.
I did. This part is fixed, but the whole thing is still getting hung up on something else. I'm going to play with it more after work.
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Old 08-21-2019, 10:51 AM   #20
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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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Old 08-21-2019, 01:32 PM   #21
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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.
Do you have any experience with removing the number wheels from these later clusters? It looks like a pretty sealed unit to prevent tampering.
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Old 08-21-2019, 01:48 PM   #22
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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.
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Old 08-22-2019, 09:51 AM   #23
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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!
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Old 12-20-2019, 06:04 PM   #24
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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.
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Old 12-20-2019, 10:27 PM   #25
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