deimos

I spent an hour debugging my speedo/odo/temp gauge problems on my '84. Conveniently, they all seem to connect through the same 14 pin connector on the left of the gauge pod (gauges installed normally). I can't tell from the workshop manuals if this is correct or not.

I've been able to trace the wires onto the white relay board, and the voltages are consistent throughout. All grounds show continuity between each other.

My next step is to bypass the relay board altogether and wire direct from the speed sensor to the 14 pin connector to see if that helps.

Should the TACHO read 2.64 volts when car is in drive (rear end is off the ground, but rear driver's tire is spinning at roughly 15 mph)? There is no voltage change when giving it gas. Voltage drops to zero when brakes are applied. Could it be a bad speed sensor?

TACHO is not tachometer, because that's on the right plug (if I pull the right plug the tach doesn't work).

The labels below are from the mylar itself where the 14 pin plug inserts into.

Description:Pin#:Idling Voltage:Driving Voltage
TEMPGAUGE:1:0:0
TACHO:2:2.6:1.3
NULLSTELLUNG:3:0:0
TANKWARNUNG:4:0:0
TANKGAUGE:5:0:0 (this can't be gas gauge, unless 0 volts means full tank, which is correct)
BEGRENZUNGSL:6:0:0
KUEHLWASSER:7:0:0
KUEHLWASSER:8:12.5:12.7
TEMPWARNUNG:9:0:0
WASCHWASSER:10:0:0
TEMPGAUGE:11:0:0 (funny, this reads redhot on the gauge)
BLINKER:12:12.8:12.7 (fluctuates between 3 and 12 with hazards engaged)
BLINKER:13:12.6:12.7 (fluctuates between 3 and 12 with turn signal engaged)

This is the 6 pin connector in back in the spare tire wheel well, the 4 pin appears to be for fuel pump but reads all zero all the time (yet, fuel pump works fine).

6-pin connector wire color:Idling Voltage:Driving Voltage

BLACK Wire:0:0
BLK/BLU:12.0:12.0
BRN/RED:2.64:2.64 (notice this almost matches the TACHO voltage above)
BRN/RED:0.03:0.03
PURPLE:0:0
PURPLE/WHT:0:0
GREEN:0:0
BROWN:0:0

The wires match up as so:
BLACK to PURPLE
BLK/BRN to PURPLE/WHT
BRN/RED to GREEN
BRN/RED to BROWN

No idea how BLK/BLU and BRN/RED can have voltage while the other end they're plugged into cannot. I get full continuity between each wire pair, so I know they're connected inside the plug.

deimos

Just updated the original post, it's an '84. The fuses check out, the grounds check out, the wiring appears to match, whether the voltages are right or not remains to be seen. The WSM implies the speedo is based on pulses and should read 12v, mine reads 2.64v, but it reads 2.64 coming out of the sender itself.

SharkSkin

Deimos, put down the multimeter and step away from the car!

j/k

AFAIK, that 14-pin connector near the jump post has nothing to do with your speedo/odo. The speedo is based on pulses, but you're moving the wheels so fast that the multimeter is seeing AC current. Also, what you're seeing is the + signal that gets grounded intermittently by the speed sensor. BTW, the temp gauge wire should be hot. Check the engine side of that connection(while disconnected) using the ohmmeter. Check ohms when cold, warming up, then hot & post here.

Look at the procedure in the WSM, Page 27-13, troubleshooting the cruise control. It will tell you if the speed sensor is working at least to the cruise brain, which is under the console up near the firewall. It's basically the same wire that leads up to the speedo. I've done this procedure, and it's very clear and easy. If the speed sensor checks out here, you can assume the problem is not in the rear of the car anywhere.

Here's the procedure... pin numbers are on the cruise brain connector.

CHECKING MULTIPLE PIN PLUG OF CONTROL WITH AN OHMMETER AND
IGNITION TURNED OFF
1. Check ground on plug.
Display between terminal 12 and car ground should
beOohm.
2. (not relevant)
3. Connect ohmmeter between terminals 11 and 12
(speed sensor).
Push car slowly or turn one rear wheel and hold
the other rear wheel. Display of meter should
alternate between 0 and infinite ohms.

deimos

I give up. I appear to get correct ohms and voltage to the connector. I called around a few places to see if they could work on it and repair. One said that his tech's wouldn't even be as thorough as I've been, but for a lot of money per hour, he'd be happy to fix the problem, as it's most likely a dead mylar strip on the cluster.

I guess it's time to call North Hollywood and see about getting a new mylar strip. Either that or I solder in all new wires and bypass the whole mylar strip altogether.

SharkSkin

Most likely, that mylar strip just needs to be pulled out, cleaned, and put back. Might want to replace the bulbs in the cluster while you're at it. A lot of people who just have basic tinkering skills have done it...

deimos

Yeah, I've done that, twice. I've even toned it out to verify connectivity between all contacts and their destination. Replaced all the bulbs, etc. I'm debating removing the mylar and soldering in physical wires everywhere, and redoing the connector to match the wires.

SharkSkin

If all connections check out, then maybe you have a bad speedo. Also, I've heard that the solder joints on the backs of the gauges can go flakey over time. you might want to resolder those WYAIT. If you have not identified a specific problem with that mylar strip then I would recommend against chopping it up.

deimos

I think i'm going to send the whole cluster off to get tested and repaired (if needed). Everything appears to work end to end from what I can tell. When I had the speedo and temp gauge out, the soldered points appeared to be intact, and I remember doing a continuity test, which passed. However, I didn't magnify the soldered points and inspect them with any real detail.

DALEZPLACE

am a new shark owner and not an expert yet, but just for ****s and grins think you might want to try making a few ground straps and run some extra grounds... is only way i can explain how you would get different voltage on same wire at different locations...minus resistor wires (unlikely) or minimal voltage drop...couldnt be much for a short wire... as long as careful where drilling for screws cant see harm in some extra ground jumpers...maybe as temp test use test leads with alligator clips ?
have fixed alot of american car dash problems that way ... good luck will follow up curious now ...maybe my next problem...lol

SharkSkin

DO a search... someone posted pics, and mentioned that the solder joints looked fine. When I resoldered all the connections on my cruise brain to get it working, I couldn't find any problems by visual inspection, and I used to be in the PCB assembly business! If you have the unit out it's worth re-flowing the solder joints just on principle.