Another B4 Speedometer Issue Thread - RESOLVED

turbodieseldyke

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Have you desoldered anything from this board yet? Was there a capacitor in that spot before? I don't see why they would put a cap there, when it's marked for an inductor.
 

jhax

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There was what I now assume is an inductor. I desoldered it thinking it also needed replaced because the information conveyed on this thread "replace the capactorS


I used a 470uf 25v cap when I replaced mine. If you're going to do the one I would think it wise to do the other as well.

The 470uf is a Nishicon cap, the 220uf 6.3v cap was Fcon. You may not find these brands though, but I don't recall if I specifically looked for these brands either. You will have to buy a few more than you want but that just means some backup for another cluster down the road too.

I just searched on e-bay to find the ones I needed. It was 50k miles and 5 years ago and I've had no problems. When I got the cluster it squealed like a pig, so even before I powered it up I replaced the caps in hopes of salvaging the cluster...and it did.

Steve
 

jhax

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I replaced the bigger capacitor at the top already, that is soldered in. the L101 was desoldered and that smaller capacitor is just sitting in there. the C970 never had anything soldered in it to begin with.
 

turbodieseldyke

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Maybe other revisions had a 2nd cap in the C970 spot. If that's indeed a "C". Can't see it in your pic, but it is marked as polarized. No sense in "replacing" what was never installed in your board.

But yeah, put your inductor back in. Do you have a pic of that board, before you worked on it?
 

jhax

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Well hopefully I can get this inductor back on, are those polarized? I dont see any indication on it that it is, just a semi opaque plastic housing with a copper coil wrapped around inside it.
 

Steve Addy

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So when it was mentioned to change BOTH capacitors in the top right corner. That is incorrect? Really it is changing ONE capacitor? I am confused.
I changed both capacitors, and I think the caps are keyed to the stripe on the plastic cover. The 0 on the stripe IIRC means ground.

I've never seen a C970 with anything mounted to it, and on my board the smaller was a cap, so it got a cap replacement 50k miles ago and nothing has complained since, and when I got it it squealed like a banshee.

Streve
 

Steve Addy

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Well hopefully I can get this inductor back on, are those polarized? I dont see any indication on it that it is, just a semi opaque plastic housing with a copper coil wrapped around inside it.
Post a photo the object you removed from the smaller mounting, that will be the easiest way to determine what needs to go there.

Steve
 

turbodieseldyke

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I’m no electronics expert, but I thought this style cap, is definitely polarized….
Inductors are not polarized. The 2 caps in his pic are polarized.

Three things make me think an inductor belongs there.
1. Board layout is marked for inductor [["L101"]]
2. The item he described sounds like an inductor [["opaque plastic housing with a copper coil wrapped around inside it"]]
3. Board layout is not polarized for L101, while there are polarized markings for 970 below it. (C970? Can't see the C in his pic)

I'm a bit surprised he didn't mention earlier that his new cap looks so much different from the old "cap" he desoldered.
 

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This is from another thread, unfortunately it's not clear enough to show us what is there. I can see though that there is a smaller cap on the other side of the stepper motor.

It's been so long since I was in to mine I can't say for certain what the layout is, TDD might be right. I don't even know if my Chubbs MFA cluster is even here at the house, it may have been taken to the shop pending install in the wagon. TBH I don't have a B4 cluster to look at so I cannot contribute anything at 100% assurance.

Steve

 

turbodieseldyke

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It does show C970 though. I could only assume the C before because of the polarity mark. That cements my thought that C means Capacitor, and L still means Inductor, even on a German circuit.
 

jhax

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I put it all back together it was an inductor there, my board looks like the photo above only 1 capacitor the C970 (furthest space on the right) did not originally have a cap also like the picture above.
 

Steve Addy

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I put it all back together it was an inductor there, my board looks like the photo above only 1 capacitor the C970 (furthest space on the right) did not originally have a cap also like the picture above.
You do have two caps, but the second smaller one is in a slightly different location.

As shown here:



Steve
 

jhax

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Son of a... no its still on my bench ill take it apart again
 

Steve Addy

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I found a couple clusters at the house. I thought I'd moved all of them to the shop but I didn't. Took these pictures for others to see what's there.





I didn't dismantle the cluster completely, just pulled the tach needle and faceplate so I could get a good pic of the caps.

Steve
 

ToddA1

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So, those caps can be swapped, without removing the tach stepper? Doesn’t appear to be too hard, if so.

-Todd
 

Steve Addy

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So, those caps can be swapped, without removing the tach stepper? Doesn’t appear to be too hard, if so.

-Todd
The cluster in my wagon got dismantled in order to replace the caps, but I never had to remove the stepper to do it, only the housing / lens and the white bits that surround the stepper.

Steve
 

ToddA1

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Good to know. I’ve always sent mine out, because I didn’t want to get involved, lol. Lazy…

-Todd
 

jhax

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I never even removed the white plastic that is on the board. I had enough room to desolder the large cap from the bottom of the board.
 

jhax

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Well that's a no go. Plugged the cluster displays are blank until key on, then they display as they should, heard the whirring noise, started it up no tach drove a few yards, no speedo. When I initially removed the tach needle it took the stepper motor cover with it. There are 2 gears one attaches to the center of the motor on the bottom and the other is offset. I know the offset gear is facing the correct way and I am 99% sure the main gear is on the right way as the top gear spins based on the first gear. Do you all suspect my elmos is shot? There are no indications of burning chips.
 

roadrunner89

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@jhax sorry, I've forgotten to take a photo of the specific PCB.
Do you still need one?

Depending on the revision, the two caps are placed around the elmos chip.
Some boards have markings for the polarisation, but some don't. So it's best to mark the polarisation before.
 

jhax

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I managed to figure out the caps, although now I do not have a speedo or tach, I still have odometer and clock so at this point I think the issue may be in the ELMOS. Symptoms include, grinding from cluster at key on and it seems like I can hear the stepper motor rotating and catching. What can I do to troubleshoot further?
 

jhax

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So I just checked the resistance on the larger cap and it is showing 1.5Ohms which I suspect I do not want. Can I get a confirmation?
 

turbodieseldyke

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I think you want it to have low resistance. High resistance means the capacitor would be sucking power out of your circuit at all times. Looking at a circuit diagram, it has an entry point, and an exit. Electricity goes in, and then comes out, with no changes in voltage or amps. Just a little bit smoothed out and stabilized.

I'm not an electrician, but that's my guess.

 

jhax

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Status update: I flipped the middle gear on the speedo and tested each gauge by hand and verified the sweep manually. I would like to know what the two screws that affix the board to the plastic housing and subsequent metal tabs in the top left corner do? Power? Ground? CLuster plugged in, key on, gear whir sound, clocks turn on and display properly. Replaced a blown fuse 21 so now I have clocks with vehicle off. No response from fuel gauge now. Drive around the block, tach works, clocks and mileage counters work. No speedo, no fuel gauge didnt give it a chance to warm up to test thermostat. As slow down I can hear clicking from the speedo gear. is there a way to ensure the gears mesh? What more can we rule out at this point?

Thank you
 
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turbodieseldyke

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I would like to know what the two screws that affix the board to the plastic housing and subsequent metal tabs in the top left corner do? Power? Ground?
Without looking at it, I'd say they affix the board to the plastic housing. Nothing electrical + or - is running through the plastic. The metal tabs are probably acting as washers for the screws.
 

Steve Addy

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Status update: I flipped the middle gear on the speedo and tested each gauge by hand and verified the sweep manually. I would like to know what the two screws that affix the board to the plastic housing and subsequent metal tabs in the top left corner do? Power? Ground? CLuster plugged in, key on, gear whir sound, clocks turn on and display properly. Replaced a blown fuse 21 so now I have clocks with vehicle off. No response from fuel gauge now. Drive around the block, tach works, clocks and mileage counters work. No speedo, no fuel gauge didnt give it a chance to warm up to test thermostat. As slow down I can hear clicking from the speedo gear. is there a way to ensure the gears mesh? What more can we rule out at this point?

Thank you
That sounds like progress to me....

Steve
 
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