speedo change
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Mrkjblue
New member
Should take less than 5mins.
Speedo just pulls straight out. if stiff than wrap a large screwdriver blade in electrical tape and lever out or can push from front luggage compartment if needed. then just swop over cables/rubber trim and push back in.
Can I ask what is wrong with the old one? I had mine apart last month for a few repairs.
Speedo just pulls straight out. if stiff than wrap a large screwdriver blade in electrical tape and lever out or can push from front luggage compartment if needed. then just swop over cables/rubber trim and push back in.
Can I ask what is wrong with the old one? I had mine apart last month for a few repairs.
Guest
New member
The story is that when I bought the car it had a tempory speedo fitted whilst the origional one was being rebuilt by porsch-apart. The temp speedo was not reading the correct speed.
I put the origional one in on friday and it still reads the wrong speed. I'm sure 4000rpm in 5th is more than 75mph! When I changed the speedo there was a red/black wire to one of the terminals which had split and I though this was the reason for the misreading, although repairing this made no difference. On the back of the speedo there are four terminals (ignoring the bulbs). The red/black wire goes to the one on the right, three browns go to the one on the left and a single brown goes to the second from the left. Should there be a wire to the 4th terminal hiding behind the dash somewhere?
Thanks,
Chris.
PS Bones, when I get this sorted you are welcome to the spare speedo. It is a bit rusty around the bezel and the mile counter does not work (although this may have been due to the split red/black wire). Pmail me with your adress and I'll send it to you when I've fixed this problem.
I put the origional one in on friday and it still reads the wrong speed. I'm sure 4000rpm in 5th is more than 75mph! When I changed the speedo there was a red/black wire to one of the terminals which had split and I though this was the reason for the misreading, although repairing this made no difference. On the back of the speedo there are four terminals (ignoring the bulbs). The red/black wire goes to the one on the right, three browns go to the one on the left and a single brown goes to the second from the left. Should there be a wire to the 4th terminal hiding behind the dash somewhere?
Thanks,
Chris.
PS Bones, when I get this sorted you are welcome to the spare speedo. It is a bit rusty around the bezel and the mile counter does not work (although this may have been due to the split red/black wire). Pmail me with your adress and I'll send it to you when I've fixed this problem.
bones
New member
I'd appreciate that Chris, thanks a lot. At 4,000 in 5th you should be travelling at about 90mph. The red and black wire is the 12volt supply. I'll check the back of my speedo later if I get time and post what I find. I'm not bad at reading wiring diagrams but mine confusingly has two red and black wires so I'm baffled?! It's important not to get this wrong or you can destroy the chip on the speedo PCB.
As for the speedo reading out by so much ask Porsch-Apart if they calibrated the speedo, I doubt it as this is specialist work unless they sent it away. The speedo picks up pulses from a disk with magnets on in the gearbox. It is possible for these to drop a magnet I believe (though rare) Next item to replace is the sender, this is a fairly simple job but persevere with the clock I think that's where the problem is, I'll post later if I get into the garage today.
As for the speedo reading out by so much ask Porsch-Apart if they calibrated the speedo, I doubt it as this is specialist work unless they sent it away. The speedo picks up pulses from a disk with magnets on in the gearbox. It is possible for these to drop a magnet I believe (though rare) Next item to replace is the sender, this is a fairly simple job but persevere with the clock I think that's where the problem is, I'll post later if I get into the garage today.
Guest
New member
Interestingly, the speedo that was in the car when I bought it was reading correctly until I had driven it 50 miles or so. I doubt the problem is miss calibration as both speedos are wrong by the same amount. Thanks for looking at the back of yours for me. Let me know what you find.
bones
New member
If both clocks read the same Chris I would start by changing the sender. Remembering that my car is a '78 here's what I found behind the clock. The three joined together brown leads in my car are three brown (earth) plus one brown/red wire 'piggie backed' onto them in
Pos 1 (call this terminal Pos 1).
Pos 2 is another brown/red wire (pulse).
Pos 3 is a black wire.
Pos 4 is red/black wire and is the 12volt supply. I'll see if I can make some more sense of the wiring diagram now. The Haynes manual gives the best diagram of the instruments and senders I've seen but it still doesn't say show what goes where on the clock terminals. How is your clock wired?
Pos 1 (call this terminal Pos 1).
Pos 2 is another brown/red wire (pulse).
Pos 3 is a black wire.
Pos 4 is red/black wire and is the 12volt supply. I'll see if I can make some more sense of the wiring diagram now. The Haynes manual gives the best diagram of the instruments and senders I've seen but it still doesn't say show what goes where on the clock terminals. How is your clock wired?
bones
New member
The sender is located on the drivers side of the gearbox near the driveshaft, it's a circular item with two wires coming out of it, eventually passing through the tunnel and fastening into a two socket connector. It simply unplugs in the tunnel and a single (screw/bolt) holds the sender on at the gearbox end - from memory) as to cost I have no idea but you could try a breakers if they are expensive. You are missing a wire though unless the system is different on an 81. In the Haynes which has a very good instrument wiring diagram (for once) the black wire is not present. If you don't have a copy send me an email and I'll scan it for you.
bones
New member
Just stating the figures for the 5 speed box shown in the graphs from my '78 owners manual John. Can't understand your contempt for the sporto' box from both an engineering and useage perspective it's an ingenious, reliable and well thought out system providing gear changes as quick as you can move the stick. I defy anyone to change gear more quickly in a manual box. It also has a famous race victory to it's credit.
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