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SpeedO works but OdoM does not.

 
Old 02-23-2019, 11:50 AM
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JayPoorJay
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Default SpeedO works but OdoM does not.

Hello All.

It's been a while for me but I am finally taking my 1986 928 over to Queens NY to have it inspected to take her from a "salvage title" to a "working/active title". I've driven her for the first times these last days! What an awesome (and more physical than I would have imagined) ride. And powerful! I have been shocked by that...

I have no dash lights. Maybe its connected to my next problem, and subject of this post, maybe not. I'm going to work on the dash lights today.

My speedometer works fine BUT my odometer does not register... Trip or main. Where do I need to start looking for a solution to that.

Super grateful for any and all suggestions.
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Old 02-23-2019, 12:10 PM
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Tons of threads on odometer gear replacement. I'm sure if you do a search you'll find the process laid out. Requires removal of the inst pod, and partial disassembly of the speedo. Not hard work, but detailed. Odo gears are avail for a reasonable price.
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Old 02-24-2019, 08:45 AM
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Odometer is mechanical and the speedo is electronic and uses pulses so the two are unrelated in the 928. As mentioned you need to repair or replace the odometer gear, then never press the reset button when moving (or really ever).
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Old 02-24-2019, 10:26 AM
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Hi! Thank you both!

Knowing is half the battle... As y'all have said, I now see that there is lots of information available... Doesn't look like a very fun job, lol. But, I gotta do it. Thank you.

Btw. I seem to have fixed the problem with the dash lights. The drivers side rheostat is/was a mess. I really didn't see anyway to pull it. I was a little surprised by that. One of the two wires,,, the 13.25v,,, was hanging and it looked like the PO had tied onto the line for a power source for something. Anyway, I bypassed the rheostat and there was light, low and behold, light on the dash and other buttons and *****. Does/should the climate control illuminate???

The instrument panel is lit like a stage. Are there back lights for the instruments? I noticed a second rheostat (and a small button) more on the passenger side of the console/cluster and wasn't able to see or find use for either. Any pointers?

Then there is more. More threads to come, for sure
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Old 02-24-2019, 10:31 AM
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Originally Posted by JayPoorJay View Post
Hi! Thank you both!

Knowing is half the battle... As y'all have said, I now see that there is lots of information available... Doesn't look like a very fun job, lol. But, I gotta do it. Thank you.

Btw. I seem to have fixed the problem with the dash lights. The drivers side rheostat is/was a mess. I really didn't see anyway to pull it. I was a little surprised by that. One of the two wires,,, the 13.25v,,, was hanging and it looked like the PO had tied onto the line for a power source for something. Anyway, I bypassed the rheostat and there was light, low and behold, light on the dash and other buttons and *****. Does/should the climate control illuminate???

The instrument panel is lit like a stage. Are there back lights for the instruments? I noticed a second rheostat (and a small button) more on the passenger side of the console/cluster and wasn't able to see or find use for either. Any pointers?

Then there is more. More threads to come, for sure
If bypassing the rheostat works, then the rheostat is probably bad or corroded. You can remove it and try to clean and refurb it with Deoxit. The pod lights are 3 wedge bulbs that light the whole cluster, then there are bulbs in the back for the individual warning lights.
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Old 02-24-2019, 07:42 PM
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Dwayne's Garage has a great write up on the odo gear. There's a link to his site in the 'new visitor' sticky.

When you pull the pod to do the odo gear, you will be able to see how the dash dimmer comes out, and is wired. It's pretty basic.

Wheel on the right is intermittent wiper control (push down on the wiper stalk for intermittent).
Little button is for the intensive washer

Climate control lighting is separate. And a pain to fix.
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Old 02-25-2019, 10:31 AM
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Just an FYI, this could also be a bad switching circuit on the small ODO circuit board that runs the ODO motor.
Most likely it is the gear, however look closely at the circuit board on the back of the spedo for burnt components especially if the gear looks good

Dave K
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Old 02-25-2019, 05:11 PM
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Looks like I will be going in the direction of pulling the instrument cluster soon. For now I am satisfied with bypassing the rheostat for the dimmer. I wont need to dim lights. Its right just the way it is. I also have a fuel gauge that does not work... I have tried to cross wire at the sending unit at the tank and get no movement at the needle. Leads me to believe there is a problem at the cluster back and or gauge itself. Before removing the cluster,,, I will try to have replacement parts for the OdO... Thank you for ALL of the great advice...

GOOD news is the lights in the climate control panel POPPED on while driving. Seems removing and cleaning up ALL of the fuses and relays (replacing a few relays) did her some good. I might be wrong BUT it seems my heater/blower fan only is making contact on speeds 3 and 4. 2 and 1 are either to slow to hear and feel or they are not engaging at all.
~Going to have to unclog the drains in my sun roof. Learned that the hard way.
~figure out problems with the hatch locking mechanisms No fun considering the car was hit on the right rear corner.

Got a ways to go,,,, but it'll ALL be worth it. Already love the feel of driving this amazing machine!

Last edited by JayPoorJay; 02-25-2019 at 08:17 PM.
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Old 02-25-2019, 06:32 PM
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There are three light tunnels which guide light from incandescent bulbs down in a well. Now is a good time to coat those light tunnels with aluminum foil. Just glue it right on there, but be careful not to put it where it could short out anything. Trim it well before gluing. Others have also gone to the extra work of replacing the illumination bulbs with red or white LEDs. Also, now is a good time to insure all your check bulbs, and your shifter bulbs are working. Replace any check bulbs and shift indicator bulbs that have failed. Common that the "D" bulb is out as that is the one that gets the most use. This can all be done when you have the pod out, and sitting on the kitchen table.
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Old 02-25-2019, 08:15 PM
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All great advice and info.

It's a five speed. I've noticed the orangish upshift light working and,,, when first trying to get used to taking off in 2nd and stalling her,,, lol,,, it seemed that all of the dash warning lights were working. How can one tell if all are not? I would love to get my hands on some right colored blue LEDs and an LED rheostat for dimming while I'm there. She's Prussian Blue. And yes, no matter what, I will use the reflective foil trick...thx

Any top secret information you (or anyone) can share about approaching and tackling the fuel gauge issue? Perhaps I'll start a new thread but since I'm here...
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Old 02-25-2019, 08:56 PM
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Please do search, like before. You will find plenty of details on swapping for LED lamps. Also on fuel level sender checking. It comes out very easy from the hatch area. Replacement senders are easy to find, or you can get a new one from Roger, 928srus.com. Note that 'dimming' and LEDs is a somewhat questionable setup. Some dim better than others. Some don't dim at all.
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Old 02-25-2019, 08:58 PM
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Understood x3... Thanks
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