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Welp its been along time since i posted but the speedo just died and my tac is still dead. In the meantime my dad also bought a 1983 928 auto in a gold color.
The speedo worked before last night but it only worked past 20mph (it would sit at 0 till it jumped up to 20)
The tac only worked randomly when the temperature was warm and it would cut out alot too.
Last night i removed the pod hoping the bolts on the back of the circuit board just had a bad connection but they were all clean. So I rubbed them all down with alcohol and tightened the bolts down alittle.
Then I pluged everything back in flawlessly, the tac was still dead. When i drove off the speedo wasent working and this-morning the speedo still isnt working. But the speedo has just died randomly in the cold morning before so hopefully its just that
Ill post later today and update if the speedo is dead still.
I don't claim to know anything about OBs, but "seemed plugged in fine" doesn't tell us much. At the least you need a circuit tester, and DVmeter. If it was just the tac I'd say CPS, checking signal at the computer. Since the engine is running normally, it might just be a ground or connection. IIRC there is speedo wire in batt compartment.
Purely a guess, but I think that the tach and speedo are 2 different problems.
Which "bolts" on the back of the circuit board are you talking about?
There are rivets, not bolts, that carry the current through the plastic to the "hard board" and to the speedo. They can look shiny and clean, but still not have a connection. A DVM is the only way to tell.
Your speedo symptoms are similar to mine (bouncy, works only above a certain speed, starts working after it warms up) and all I did was follow Dwayne's writeup and solder the rivets. Dwayne's stuff is linked in the "New Visitor" sticky.
The impulse sender attached to the back of the diff may have died on yours.
Also, another failure point is the long pins that go inside of the speedometer on the PCB. All you need to do is solder them to the hard circuit board they are riveted to.
i cleaned them all with rubbing alcohol and tightened them back up.
as for the computer (thats under the passenger foot well right) what wire sends a single to the tac and speedo?
Im going to read the guide on resoldering and see what that says.
"Also, another failure point is the long pins that go inside of the speedometer on the PCB. All you need to do is solder them to the hard circuit board they are riveted to."
Yours looks different from mine - but as far as I can tell from the pic, you need to resolder the rivets and possibly the islands under the four Philips screws (two each at the far left and right edges) that make the electrical ground contacts and under the nuts that hold the tach in place. The flathead screws appear to only hold the gauges in place. In the picture I can see four rivets on the speedo and four nuts that hold the tach (can't tell what's under the gold-colored stickies).
Remove the screws and nuts, carefully touch up the solder islands on which they rest on the PCB film with a low-wattage soldering iron (30W or less - anythign higher here will burn right through, using mutil-core resin flux solder only), clean up the flux residue with pure isopropyl alcohol, put a serrated spring washer underneath each one if they don't already have one and retighten. Alternatively, you may want to disassemble the whole thing and also redo all solder sonnections for the three black large connectors that you see (they are soldered on from the other side).
The bolts are the connections for the tach. I'd use a real contact cleaner, like DeOxit, rather than alcohol.
The rivets for the speedo are on the left, above your thumb. They go through the plastic and attach to the little "hard board" underneath. You can just barely see it under the plastic.
The "long pins" are on the back of the hard board, they go into the speedo itself.
Read Dwayne's writeup and it will all be very clear.
Thanks for the responses, i grabbed some flux and some "radioshack" branded contact cleaner. Dont know if thats as great as Qrc or DeOxit. Ill post updates on the weekend when i get a chance!
So im going to dive into the pod hopefuly tomorrow. But when i was driving i noticed if i turn on the lights the engine temp gass oil pressure and voltage (voltage was the only pne that made since) goes up alittle bit. This happen for anyone els?
All right did all the stuff from Dwayn's write up and no luck.
Man flux makes soldering so easy its almost cheating
Cleaned all these bolts with some Crc cleaner
And i checked the resistance on every damn possible connection and they all had .5-.10 ohms
Also afterwards i check to see if the tac was getting voltage and it was getting 12v 12v and like .6-1.2v
Can anyone give me an idea? I thought maybe the tac and speedo somehow are just both dead.
Also can anyone point me in the direction of where the tac hooks up (couldnt find anything on the distributor) and where the speedo hooks up (cant see anything in the battery compartment).
Tach signal comes from the ignition module on the passenger's side fender wall and the speedo signal comes form a sensor on the back of the differential cover on the transmission.
I resoldered the pins and rivets for the speedo, it works now.
I re soldered a quick connect on the tachometer and it still does not work.
But the **** lift works when i asume it should.
im starting to think this tac is just dead. Any pointers on how to go about refurbishing the tac or finding a new one?
01-26-2015, 01:47 PM
Speedo and Tac
