[BillW]

I have a 1991 Dodge Caravan that the speedo has quit working. The speedo used to act up when very hot outside now it has quit working all together (it would stick at aroound 45 and at zero). Any tips as to what to look for?

 

[John Wood]

Does your odometer work? If both are out, check to see if you have a code 15 stored (it will probably not light the CEL on a 1991). If the code is there, you probably have a bad speed sensor on the transaxle. If your cruise still works, your speed sensor is good and the problem could be a bad connection to the speedometer head or bad solder joints on the cluster board. It is always possible that the movement is bad, especially if the odometer still works.
...and if the odometer works, pull the unit out of the cluster and check for a frozen needle. Perhaps a drop of very thin oil could get it going again (electric shaver oil or sewing machine oil, but just 1 drop and it might stain the bezel).

 

[BillW]

Does your odometer work? If both are out, check to see if you have a code 15 stored (it will probably not light the CEL on a 1991). If the code is there, you probably have a bad speed sensor on the transaxle. If your cruise still works, your speed sensor is good and the problem could be a bad connection to the speedometer head or bad solder joints on the cluster board. It is always possible that the movement is bad, especially if the odometer still works.
...and if the odometer works, pull the unit out of the cluster and check for a frozen needle. Perhaps a drop of very thin oil could get it going again (electric shaver oil or sewing machine oil, but just 1 drop and it might stain the bezel).

Thanks for the reply. The cruise and odometer are also out so I guess that means the speed sensor. Now the question is, which of the three sensors is the speed sensor?

 

[KOG]

On a 91 it's on the right output shaft (driveshaft) housing on the rear of the transmission.

 

[John Wood]

On a 91 it's on the right output shaft (driveshaft) housing on the rear of the transmission.

Just to add... the sensor is at the top of the transaxle tail piece and is held in by 1 small bolt that uses a 10 mm socket. You will probably need to pull and twist it as you pull up, and expect a little transmission oil to come out. The O-ring may cause it to stick a little. There is a 2 wire electrical connector with a retaining tab. Try not to break the tab. Sometimes the connector gets dirty and can cause the same problem. A dealer replacement unit will likely come with a new improved wiring harness pigtail that can be soldered in, in-place of the existing connector. This is referred to a service package in the part description. Some after market sensors just come with an adapter to go from the old style plug to the new style connector on the sensor.

 

[ImperialCrown]

The plastic gear can also wear enough that it will lose contact with the mating worm gear on the axle joint. The plastic teeth may have a slightly concave appearance.
With the ign on and a helper watching the speedometer, give the gear a spin with your fingers and see if the speedo needle moves. This would prove that the speed sensor is working and that the gear may be the culprit.

 

[BillW]

Thanks to everyone that has replied. I'll have some time to work on this finally. Wish me luck and thanks again.