jpitman2

Was forced into a pod removal because ign switch went intermittent. Its in now. Put leds in the light sockets, tested them for polarity. Have cleaned the ground under the column. Cleaned the pcb contact traces carefully, and the connectors (brush with emery board).
In testing the dash light connections (blue/black +12V, brown ground ) at R14 and R13, found odd things. 1.4Meg ohm R13 to ground, 4 Ohms R13 to ground with dimmer shorted out. Wiring diag shows R13 bridged to R9 and grounded at 3(column), but the readings dont match this.
Initially connecting dash and then battery, all seemed OK, all warning lights came up, dash lights there but poor. removed all again to try normal bulbs at 5W vs the leds, reconnect and I get fuel gauge pegging when I turn on sidelights! Drops to zero when lights go off, but pauses for a few seconds.
From all I have read here, many strange dash things come from bad grounds....
R9 is shown as ground for:-
hi beam inidcator
voltmeter
oil press
tacho

R13 is ground for:-
dash lights
speedo
fuel gauge
temp gauge, warning.

Testing R13 to R9 on the pcb shows a low reading, but not zero.
Have in the past had the following issues:-
temp gauge kicks up a bit when lights turned on
voltmeter reads erratically, up to 16V(where a dvm in the cigar lighter reads ~14V)
dash light dimmer has been shorted out.

Couple of questions
- where to look first?
- can I safely bridge R13 to R9 for a good ground for the lights, and all the other things that depend on it being grounded?
- I have seen a pic of the vertical connector socket stabilized to the pcb with silicon? Mine is very wobbly on the board - is trying to stabilize it safe and wise?
tks
jp 83 Euro S AT 53k

Mrmerlin

its quite possible you damaged the connectors i would suggest to only clean the connections on the POD with an eraser then wipe with a alcohol soaked Q tip.
If you pressed an emery board into the female connectors its possible that the connector pins are pushed open too far to make contact or there is emery particles in the connectors

jpitman2

Probed R13 from the front (PCB side) and the rear of the connector, disconnected from dash, same result.
jp

Ed Scherer

I'm not sure if the connectors are keyed or not, but are you sure that you don't have connectors #3 and #4 swapped?

The reason I mention it is that terminal #16 on connector #4 is for fuel level sender, and terminal #16 on connector #3 is for side marker light failure. And based on this:
it sounds like you're describing a scenario where those might be crossed.

Seems like way more stuff would go wrong (especially since terminal #14 on connector #4 is the power source for instrument cluster backlighting), but I think most everything else on connectors #3 and #4 are fault or other indicator inputs.


I was rather paranoid about the connectors (and didn't know whether or not they were keyed), so I improved the labeling:

jpitman2

Wrong model, this is an 83, with only 3 connectors, named Left, Right (both up from underneath), Middle(vertical, on right side), pins numbered up to 14 only. Have NOT moved any wires in connectors.
jp 83 Euro S AT 53k

Ed Scherer

Ahhh... that changes everything.

Saw the:
in the O.P. and thought I might know something.

With an 83, well... I know nothing.

Good luck, anyway.

jpitman2

Sorry about the typo, fixed now.
jp

jpitman2

Update. Found that r13 and R9 are joined in the mylar with a trace, so probing the connector was useless. Connecting all up, and powering gives me all warning lights (I think), but turning on side lights pegs fuel gauge still.
Possibilities :-
- one connector is reversed (180 degrees out) - doubtful , but possible. Will check wire colours match.
- connector is offset sideways, connecting to wrong pins - is this physically possible?
??
Right connector seems to number from R->L (ie R14 is most inboard) - sound right? Will use wire colours to check Left and middle connectors.
No more ideas out there ?
jp 83 Euro S AT 53k

jpitman2

Another update. Overnight it occurred to me that the gas gauge pegging being triggered by turning on side lights might be caused by the proximity of the sidelight annunciator to the gauge on the dash. Sure enough the gas gauge is fed by L5 connection, annunciator light by L6. Smells like some sort of short across those two connectors....will examine the plug asap.
BTW, how do you get the pins out of these plugs - there is a sort of clip on the back, with 3 fingers in it, in the centre, but ? Tried pushing in beside the pin on the board side, but nothing seemed to move, as it might if a something needed to be lifted to release the pin.
jp 83 Euro S AT 53k.

heinrich

Ed why the pic of Rod Stewart in your avatar?

Maleficio

I was about to say it sounds like you've provided a solid ground to your fuel gauge causing it to peg.

jpitman2

I think its more like +12V. I wonder if there is room for the connector to slip sideways at all , but still appear ok?
jp

jpitman2

No visible shorts between L5 and L6. Each to ground shows some resistance - the sidelight bulb shows ~10 Ohms, the gas gauge ~85 ohms. Probing the pins in the connector shows the gas gauge sensor around 50 ohms, which is fair seeing as its range is 0-80 ohms last I had it out.
Next curiosity - power on, sidelights on, gas gauge pegged - turn ign on (ie ready to start), gas gauge drops to a sensible reading, oil pressure gauge jumps a bit. Turning off sidelights with ign on, gas gauge kicks UP, oil press kicks DOWN.....
I smell an earth problem somewhere, or maybe a short. Has it happened because I have disturbed stuff? Only issue that got me here was failing ign switch, now replaced with new.
Couldnt be a rong switch could it - old was 928 613 017 01, new is 964 613 012 00. Is the switch necessary to supply base 12V to all devices, even when key is off?
Where is ground point 2, under which splash shield?
jp 83 Euro S 53k, not happy!

tmpusfugit

I fought pod and gauge issues for sometime in my '84 with symptoms much like yours. All my pod gauge wires had been cut off when I bought the car as the PO was going to use a much different approach, but he gave up on that and sold me his car....I rewired the original connectors (which fortunately he had saved with enough wire left on them I could butt connect and shrink wrap back to original configuration).

After all that was done, I had problems like yours. Days of troubleshooting (and just plain guessing) I concluded it had to be the ground wires to the pod, yet everything on the pod was correct, and all the wiring was correct.

Long story shortened here....either PO or I, had shoved test probes into the plug that connects to the pod and had distorted the plug on the harness untill it did not make contact when plugged into the pod. On the '84 these were terminals 9 and 13 on the right hand pod connector. It gave me all sorts of crazy indications and I wasted days on the problem. I actually bought another pod that had precisely the same problems.....2 minutes to carefully reform the contact pins, and all was well. Of course, after putting it all back together and patting myself on the back 2 weeks later the speedo drive gear fell apart, so out came the pod again, for about the 40th time....it gets easier everytime by the way!

Check your 9 and 13 pins just to see if they are deformed, it sounds like they could be...they bend very easily and it is not obvious they are not connecting....

jpitman2

Jim, thats the most useful suggestion so far, thanks. The symptom is fully consistent with a ground failure at R13, R9, and the current is finding another way home. I was actually wondering how to bend the plug connectors on the way in this morning, without fully dismantling the plugs - but how? Remove the little claw thing at the back? Maybe slip something thin (1/16"?) under the mylar to push the traces up?
jp 83 Euro S AT 53k