Tach and ODO Issues
 

All-

I'm trying to figure out what is going on with my tachometer and odometer. The last year or two I haven't had much chance to drive my 1987 928 S4 automatic as much as I would have liked. I notice some of the instrument cluster started to work intermittently. Speedo, fuel gauge. But the tach went out a year or so ago. I also noticed the odometer hasn't moved in a long time either. I've taken the pod out and cleaned it before, so not a huge deal. I did it again over the the winter. And while the speedo and fuel gauge still aren't perfect, the cleaning and driving it more seems to have them working more often. But still no luck on the tach and odo. I know I cleaned everything really well, so I don't think it is any connections on the cluster. or the connections behind the pod.

Is there anything else I am missing? It's been a couple years since I cleaned all the grounds. Could that be it? It hasn't been that long. Someone at a PCA meet-up mentioned there is something down near the transmission I might want to check. I need to do an oil change, so maybe there is somewhere I should look at while I'm under there.

Or maybe just part of the cluster is just dead and I should send it out to be checked/repaired. I'm only semi-handy. Odds are about 50/50 that when I start to pull stuff apart that I will make things better versus make it worse.

Any help is greatly appreciated. I like having everything working and I loved it when I didn't have any of these issues for years. But I guess that is what I get for not driving it much lately. Hopefully that will change this year.

Thanks in advance.

Honestly, I would take out the pod and install a new circuit panel. They are inexpensive for 85-88 cars compared to the rest.

Doing this will eliminate issues with it in the future because they are all on borrowed time at this point.

Huh. I didn't realize this was an option. Any particular place I should order it from? I'd have no problem doing this. I've pulled the old one off to clean it (very carefully). THat wasn't that bad as long as I was methodical and careful.

Got mine from Roger

Thanks. I shot him an email. I didn't see the thread about my year, but saw two for earlier models. I'll have to dig some more. Dang, that would have worked out great to have when I pulled the pod this past December. Oh well. Guess I should check the forum more often...

OK, I thought I'd post an update and ask for more advice. So what I have done in the last two weeks is get a new circuit board from Roger at 928sRUs (I didn't know these were available) and got a new ODO gear. Excited for both! Pulled everything apart again. Did the ODO repair (old gear was basically like clay and crumbling) and new board looks great. Unfortunately when everything is put back together, I had mixed success. Here is where things are at:

Temp Gauge: It was always fine and still working
Fuel Gauge: Was intermittent before and seems the same. Works about 50% of the time. Bounces back up from time to time.
Speedo: Seems good now. At first I thought it was intermittent but after about a 25 minute drive last night, it worked the whole time. So a victory! Yah!!
ODO: Fixed! I knew this one would work once I saw that old gear.
Tach: Nothing. Still nothing. Damn.
Oil Pressure/Voltage: Always seemed fine and still seems fine.

So with that all said, any ideas on the Fuel Gauge and the Tach? Could the Tach just be dead? What is left on my checklist to investigate?

Oh, and I noticed after last time I put the pod back together that the turn signals stopped working at the instrument cluster. Fine outside, but no blinker or noise inside. Any ideas on that? Did I forget to connect something?

Thought I would reply again to see if anyone has any more ideas and just a general update.

I've gotten a few more drives in. One of them, the speedo was pretty much off the whole time. Then the last one seemed to work the whole times. No idea what is going on. The tach is still dead as a doornail. And the fuel gauge is intermittent. If I give it a lot of gas, seems like it might cut out and then come back later. But even that is pretty inconsistent.

I'm considering removing and replacing all the pins in the connections in the back of the instrument pod. Any idea what size pins I need and where I can get those at? I've been tinkering with some other electrical molex connectors with some arcade games and think this might be a good step. Thoughts?

On my GTS I had the same problems after grounding out an interior light. It was an easy fix (the #15 fuse) if I recall correctly... Hopefully works for an 87, sure worth the time to check it though.

Check fuse #24.
Jason

Thanks guys! I'll check both and report back!

Alright, sorry for the delay in reporting back. Unfortunately I checked both fuses 15 and 24 and no dice. I guess my next plans of attack are:

- Go back through and clean all the grounds again (always good to be extra sure
- Send out the tach to get checked/serviced. Any recommendations here on where to send? Or instructions on how I could bench test it myself?
- Replace pins in the connectors with new molex pins. Any idea what size pins I would need?

Thanks

-Bill

The problems may not be related.

Is there a way to check the fuel sender unit in the tank? I'm not certain of the signal 0-5 volt maybe?

Yeah, the tach, speedo, and gas gauge are not greatly inter-related on the pod circuitry, but they do all have a common ground. So, if you have not checked that, I'd go there next.
Ground Point IV. Up under the dash, near steering wheel. Take off your parcel tray (I took mine off day-one and never missed it) and if you push the drivers seat all he way back and use some gymnastics, on your back with the top of your head against the brake pedal if you look up with a flashlight it will be in your face. A billion brown wires on one bolt. 10mm socket and short extension. Go ahead and take the flashlight, socket, Deoxit or similar cleaner, wire brush and clean rag with you when you "go under." Going back and forth from that position a few times is not fun! Make sure you put all of the ring terminals

back on.
Jason

Jasonhttps://cimg2.ibsrv.net/gimg/rennlis...3dd943f95d.jpg

Hmm. I'm not sure. But I'm up for it if anyone can point me in the direction of how to do it! I think I'll try the grounds first though. Thanks for the tip!

Thanks, yeah, that sounds like a likely candidate and relatively easy. I've sat on my head a few times under there, so not a problem. My back doesn't like it the next day, but not a huge deal. And I have everything I need to get it done pretty quickly and easily, so that is good. I'll post updates when I am done!