speedo problems

[justin 620]

hello, i have a 79 620 and the speedometer doesn't work, i got a new cable for it, but it still won't work... if anybody has any ideas as to what the problem could be please inform me.

[ggzilla]

Either the speedometer is broken or the gear in the transmission is broken. It is easier to pull the gear out of the transmission and see if it is worn. They are made out of nylon.

[MikeRL411]

If the speedometer cable and nylon drive gear check out OK, you may have a cracked solder joint on the copper drag cup to needle drive shaft. The drive shaft spins a permanent magnet and the eddy currents in the drag cup move the needle. Any good speedometer shop should [but may not be willing] be able to locate the cup on the shaft and resolder it. Beats having to recertify the odometer mileage with the motor vehicle folks if you get a replacement speedometer assembly.

[banzai510(hainz)]

I disconnect the cable from the instrument cluster. then drive the rig. if cable dont spin I remove the bottom. Most time the cable splitz in half. I had one where the key nylon teeth were sheared off(it made to do this incase it jams.

 

Take the 10mm tang off and pull that whole assemble out and get another.

[justin 620]

I disconnect the cable from the instrument cluster. then drive the rig. if cable dont spin I remove the bottom. Most time the cable splitz in half. I had one where the key nylon teeth were sheared off(it made to do this incase it jams.

 

Take the 10mm tang off and pull that whole assemble out and get another.

 

ok, so i pulled the cavbe out and it's not broken. but the end that goes into the trany has a key like thing on the end, and the one that goes to the speedo doesn't... that's probably it huh?

[datsunaholic]

No, the speedo end one is just the cable, ground into a square.

 

1) Was the odometer working? If the odometer was turning but the speedo did nothing, then the problem is the speedometer.

 

2) If neither the speedo nor the odometer was working, then you need to find out if the cable was turning.

 

A) If the cable was turning but nothing from the speedo or odo, then the speedo is bad OR the cable is too short.

 

B) If the cable wasn't turning at all, the speedo cog probably sheared.

 

 

If the head unit is bad, I'd just replace it. I wouldn't worry about recalibrating the odometer unless you really want the mileage to match. Dunno about Oregon, but in WA the odometer reading is not meaningful on 10+ year old vehicles. It's possible to reset a Datsun odometer yourself anyway, I've done it many times when swapping speedometers.

[ggzilla]

Oregon is the same, no speedometer reading required for old vehicles.

 

An alternative to fixing the speedometer is to buy a tachometer.