How to fix a speedo?

[jonmorine]

Hello,

Sorry if this is a dumb question but my speedo doesn't work on my 69 and I am wondering if there are any places that I could find good instructions on fixing it? I am assuming I will need a new cable which I can find, its just I have no idea where to begin.

Thanks for your help in advance.

[okayfine]

Depends on what is wrong. It could be the cable, as they get dry over years and can snap. It could be the sender in the transmission. It could be inside the gauge itself.

What, exactly, is happening to lead you to believe your speedo is broken? It's hard to help when you haven't provided any symptoms.

[510Martinez]

Hello,

Sorry if this is a dumb question but my speedo doesn't work on my 69 and I am wondering if there are any places that I could find good instructions on fixing it? I am assuming I will need a new cable which I can find, its just I have no idea where to begin.

Thanks for your help in advance.

If its the cable you just replace that. If it's the speedo head, the average car guy does not have the correct tools or knowledge to fix it. They use a spinning magnet to move the needle and the shaft runs on a small precision bearing sleeve. There are plenty of shops that fix speedometers if it need it.

[okayfine]

If its the cable you just replace that. If it's the speedo head, the average car guy does not have the correct tools or knowledge to fix it. They use a spinning magnet to move the needle and the shaft runs on a small precision bearing sleeve. There are plenty of shops that fix speedometers if it need it.

Very true. I have that exact condition. This was one of the reasons I asked for symptoms. My ODO and Trip meters roll over as I drive, but my speedo needle doesn't move. This points directly at the speedo head, not at the cable (or the sender).

[jonmorine]

OK the symptoms are as follows: The gauge needle does not sweep at all. Also the Odometer doesn't work either.

All other parts of the instrument cluster work such as temperature, gas, blinkers, etc.

I hope this helps.

[okayfine]

Yeah, that's more likely a cable issue.

The ODO is gear-driven from the cable. The speedo needle is indirectly driven via magnets as Martinez described.

[jonmorine]

Great thanks for the info.

So it should be pretty evident when I take the cluster out what is wrong with it. Keeping my fingers crossed.

[okayfine]

No reason to take out the cluster. You should be able to get your hand up behind and unscrew the cable from the back of the speedo. Pull it backward (towards the firewall) an inch or so to pull out the drive wire, then remove through the firewall.

In fact, you likely won't be able to remove the cluster until you remove the cable.

[510Martinez]

There is another, but less likely, possibility. You could have a problem at the transmission. The cable is driven from there. First thing I would do is look to see if it's still attached and if there isn't a badly damaged gera on the cable end or in the transmission itself.

[jonmorine]

Great thanks for the info guys. I am hoping its just a snapped cable and there isn't a problem at the connection. I appreciate your wealth of knowledge.

[datzenmike]

If the outer sheath that protects the inner flexible cable is damaged, road spray will enter and collect at the lowest point. Next winter when it freezes the inner cable will twist off as soon as you drive it a few car lengths. I think NAPA still has them for around $20. If they don't go back as far as the 510 try a newer 620 truck. It will be at least a foot longer but can be zip tied out of the way.

[jonmorine]

OK so I took the cable out and it is not snapped. However it was full of oil. Well that what I think it was. I decided to replace it with a new one and still no luck. Looks like it may be a problem at the transmission. Is there an easy way to fix it at the transmission sender location?

[okayfine]

Looks like it may be a problem at the transmission. Is there an easy way to fix it at the transmission sender location?

Depends on what's wrong with it. It always depends.

That said, have you verified the cable is or is not turning underway? Remove the cable from the back of the speedo and have a friend watch the squared cable itself as you drive a short distance. The squared cable should rotate. If it does, your problem is in the gauge cluster. If it doesn't, your problem is at the tranny/sender. Easy test to point you in the correct direction.

[jonmorine]

Wow never thought of that. Thanks

[jonmorine]

OK I am learning more and more about this problem. I tried your technique and drove without it connected to the back of the speedo. The cable was not spinning. So I tried another technique. I reconnected the cable to the back of the speedometer and attached a drill to the transmission end of the cable. As soon as I gave the drill a little spin, the speedometer and odomoter needles moved. Therefore I am almost certain it is the drive in the transmission.

The next question is: how do I fix that. Its a 4 speed tranny. The only other tranny that I have seen this fixed on (non Datsun), you were able to pop the speedo gear out externally. It does not look like I can do that with this one.

Any ideas would help. My repair manual doesn't say anything about it.