It was time to remove the binnacle once more, this time to upgrade to a new instrument cluster PCB ribbon. Last time that I tried re-fitting the binnacle after the LED Upgrade I had trouble fitting the connectors and experienced some of the tabs on the ribbon crunching and bending out of their correct position. At this time my temperature gauge stopped responding. I tried tips like knocking the needle with a straightened out paperclip through the trip reset shaft hole in the binnacle lens when the car was hot, however this did not work for me. Remembering that the 42 year old PCB ribbon wasn't in the best shape I wondered if that could be the cause.
During the previous weekend's October DeLorean Eurotec meet I got myself a new PCB ribbon to fit and hoped this would resolve the temperature gauge issue.
I started by removing the binnacle from the car, unscrewing the fixing brackets and taking the instrument cluster out and setting it on a table ready for the main job. All these prior steps can be read about in my LED Upgrade post.
The upgrade could now begin. I started by getting some paper and tracing the locations of bulbs and nuts that I would remove to ensure I knew which ones were to go back into which position. Also I remembered that getting the bulb holders inserted the correct way, so each bulb's polarity was correct, was important, so that they worked before re-fitting the binnacle. To ensure I did not insert them back the wrong way I marked the side of the holder that should be on the right with yellow paint. This can be seen in the photo below.
I then peeled off the 42 year old PCB ribbon from right to left.
Laying the old and new PCB ribbons out next to one another the deterioration of the original was clear to be seen.
In particular the contacts for the black upper right connector (that comprises 12 pins of which only the lower side, 7 thru' 12 are used) had in fact worn away over time. This had me thinking that maybe when I did the LED upgrade, the copper could have cracked when I was refitting the connector.
Next was the job of refitting the new PCB ribbon. The method I used, since the new ribbon was stiff and would not stay formed into the shape of the rear of the cluster, was to work from left to right fitting the nuts as I went.
Then I refitted the bulb holders with the yellow markings to the right hand side.
All that was left now was to refit the binnacle to the dashboard and plug in the connectors, a real fiddly task that requires a lot of patience.
The photo below is taken through the windscreen of the back of the binnacle after having managed to reach and fit the two connectors. It shows the series of six wires sheathed in black tape rising to the upper right connected via the black connector, and the 16 wires to the white connector plugged vertically into the centre socket, most of which is in view.
Before finally fixing the binnacle back in place I ran the car to test the temperature sender, still no result. whilst hot I nudged the needle as mentioned in forum posts but it that did not resolve it. I checked for continuity at the no. 11 wire of the black connector to the instrument cluster, which it had. Next I would need to rule out any wider connections issues by grounding out the wire to the gauge from the sender. This is easier said than done (if you're prone to back pain as I am). As I attempted to reach the sender I felt a twinge in my back, the tell tale sign that I've pinched my sciatic nerve. That would put an end to this session, so the temperature gauge diagnostics would have to be put on hold.
For now at least, I have a nice new PCB on my instrument cluster, and also I've also reattached it with wing-nuts kindly given to me by Rob Hines at the October Eurotec Meet in Norfolk.
Below are three diagrams I have created that can be used/duplicated by anyone who wishes to use them. The specify the wires that go to which pins of the instrument cluster connectors. I've showed the colours of the wires in the same format as the wiring schematic that most of us use.
The next, black connector only has wires affixed to the second side, pins 7 thru' 12, hence only one further image below.
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