Intermittent speedometer/tachometer/fuel gauge & digital dash SEE POST #24 FOR LATEST
01-01-2011, 03:08 PM
#32
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Join Date: Dec 2009
Location: The Netherlands, Zuid Beijerland
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So, a year later I finally got around to fixing the speedo: it turns out there were three problems so I was getting a bit frustrated, but perseverence won (with help from the forum of course, thanks guys!)
In summary the problems and fixes were:
1) I replaced the speedo sensor at the back of the differential, since it was missing. I measured resistance between the connectors. By moving the car just a bit by hand you can already see it switching between open/closed.
2) flexible circuit board at the back of the instrument pod: The rivets were not making good contact with the printed circuit. Rather than soldering it I put some silver paint on it (the conductive paint you can use for fixing rear window demisters as well), and then put pliers on the rivet and firmly pressed it. The rivets now are fixed and cannot move anymore. And I used the mulitmeter to measure resistance between the rivet and the corresponding pin next to it. And also between the rivet and the connector at the plug. So, problem two tackled, but still no speedo...
3) Then I followed the wires and measured connectivity between terminals T1 and T2 and the wires to the sensor at the back of the car in the spare wheel well. (plug 'T' on the CE panel, which are in alphabetial order from left to right, skip the letter 'I' since it is not there and also skip counting the three smaller plugs. T1 and T2 are the bottom left and bottom right wires) Be sure to disconnect the wires at the back otherwise you cannot individually measure each wire that runs from the front to the back of the car. Also pull out the plug 'T' when measuring.
Resistance between T1 and one of the wires at the back was zero, so that was in fine order. The other one was not. So that is problem two. To now quickly test the speedo I ran a separate wire from the back connector to the front T2 with the T plug in place. I now got an open/close signal all the way to the pod, BUT still, when driving no speedo... By now I was getting a bit frustrated. So I put it to rest and did some further thinking. I also had no intention to pull out half my interior to run a new wire from the back to the front.
So here's the alternative solution, which I thought I would share with you, and may save you all time looking for bad ground contacts at the pod: I notived I had no wire from plug H2 (which is connected to T2 and supposed to be the ground contact for the speedo. I have read other posts saying they also did not have a H2 wire. So why on earth would one have a wire running from the speedo sensor all the way to the front of the car to the CE-panel, or even to the instrument pod to be connected to the ground contact over there? One could also connect one of the speedo sensor wires to a ground contact at the back of the car. Thus avoiding all the possible bad contact in the original set up (i.e. connectors from speedo sensor to the wire running all tha way from the back of the car to plug T2 and then from T2 to H2 and to a ground contact or even further to the pod and then to the ground contact). Sure enough: this works, provided that your other ground contact in the pod are o.k. it now ALL works. I have a working speedo, with no hesitation at all!!!
And I needed it since the yearly mandatory legal check was due and without a working speedo I cannot drive the shark...
I am one happy man. At the same time I also fixed the fuel gage (bad contacts at the rear plug.), the economy indicator (not that I am using it :-).
Only thing to do now is the odometer (the little rubbery plastic wheel has disintegrated completely).
I will post the same story in one of the other posts I used so people can use it for future reference.
And thanks to the amazing photo posts on how to take out the pod, and the practice I got, I can now take out the pod in 20 minutes or so, almost blindfolded :-) and put it back in 40 minutes.
One other thing to share: to make testing easy I took the whole pod out, and with the steering wheel of, I put the instrument panel in place with the three connector plugs. Then I lifted the rear of the car (I have a two column garage bridge at home), blocked the front wheels. Then started it and in first gear slowly turned the back wheels by touching the gas pedal. Be sure the car is properly lifted so it can in no circumstance fall to the floor and send you off into your garage wall :-) This setup can then be used for some nice trial and error diagnosis without having to take the pod out over and over again.
By for now.
Leo. 1984 euro S2, manual
In summary the problems and fixes were:
1) I replaced the speedo sensor at the back of the differential, since it was missing. I measured resistance between the connectors. By moving the car just a bit by hand you can already see it switching between open/closed.
2) flexible circuit board at the back of the instrument pod: The rivets were not making good contact with the printed circuit. Rather than soldering it I put some silver paint on it (the conductive paint you can use for fixing rear window demisters as well), and then put pliers on the rivet and firmly pressed it. The rivets now are fixed and cannot move anymore. And I used the mulitmeter to measure resistance between the rivet and the corresponding pin next to it. And also between the rivet and the connector at the plug. So, problem two tackled, but still no speedo...
3) Then I followed the wires and measured connectivity between terminals T1 and T2 and the wires to the sensor at the back of the car in the spare wheel well. (plug 'T' on the CE panel, which are in alphabetial order from left to right, skip the letter 'I' since it is not there and also skip counting the three smaller plugs. T1 and T2 are the bottom left and bottom right wires) Be sure to disconnect the wires at the back otherwise you cannot individually measure each wire that runs from the front to the back of the car. Also pull out the plug 'T' when measuring.
Resistance between T1 and one of the wires at the back was zero, so that was in fine order. The other one was not. So that is problem two. To now quickly test the speedo I ran a separate wire from the back connector to the front T2 with the T plug in place. I now got an open/close signal all the way to the pod, BUT still, when driving no speedo... By now I was getting a bit frustrated. So I put it to rest and did some further thinking. I also had no intention to pull out half my interior to run a new wire from the back to the front.
So here's the alternative solution, which I thought I would share with you, and may save you all time looking for bad ground contacts at the pod: I notived I had no wire from plug H2 (which is connected to T2 and supposed to be the ground contact for the speedo. I have read other posts saying they also did not have a H2 wire. So why on earth would one have a wire running from the speedo sensor all the way to the front of the car to the CE-panel, or even to the instrument pod to be connected to the ground contact over there? One could also connect one of the speedo sensor wires to a ground contact at the back of the car. Thus avoiding all the possible bad contact in the original set up (i.e. connectors from speedo sensor to the wire running all tha way from the back of the car to plug T2 and then from T2 to H2 and to a ground contact or even further to the pod and then to the ground contact). Sure enough: this works, provided that your other ground contact in the pod are o.k. it now ALL works. I have a working speedo, with no hesitation at all!!!
And I needed it since the yearly mandatory legal check was due and without a working speedo I cannot drive the shark...
I am one happy man. At the same time I also fixed the fuel gage (bad contacts at the rear plug.), the economy indicator (not that I am using it :-).
Only thing to do now is the odometer (the little rubbery plastic wheel has disintegrated completely).
I will post the same story in one of the other posts I used so people can use it for future reference.
And thanks to the amazing photo posts on how to take out the pod, and the practice I got, I can now take out the pod in 20 minutes or so, almost blindfolded :-) and put it back in 40 minutes.
One other thing to share: to make testing easy I took the whole pod out, and with the steering wheel of, I put the instrument panel in place with the three connector plugs. Then I lifted the rear of the car (I have a two column garage bridge at home), blocked the front wheels. Then started it and in first gear slowly turned the back wheels by touching the gas pedal. Be sure the car is properly lifted so it can in no circumstance fall to the floor and send you off into your garage wall :-) This setup can then be used for some nice trial and error diagnosis without having to take the pod out over and over again.
By for now.
Leo. 1984 euro S2, manual
07-09-2011, 02:22 AM
#33
Racer
Join Date: Mar 2009
Location: Flower Mound, TX
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I'm going to have to tackle this soon too. In my case it's only the speedo and the transmission was out recently, so probably a connection issue, but a 928 is a dangerous car to not have a speedo in, since it feels like it's barely ticking over at 100mph or so!
