hello agaIN my question is about a 240 86 the speedo works intermitenly. is there a way to check if the cable or cluster is ok iwould apreciate any info. on this thanks alot

 

There is only 3 things that could go wrong with the speedo.
The cable worn.
The speedo gear on the end of the cable at the trans.
The speedo itself.

My guess would be the Cable worn.

 

I see by your profile you have an 89 which is an electric speedo. There are only 3 connections on the back of the speedo red/blsck which supplies 12v the other two supply the signal from the speed sensor mounted on the rear end. There is also a connector where the wires come up through the trunk you will see a square black plastic box under a plastic piece under the carpet on the drivers side in the trunk. I think these wires are blue and black. blue is the signal wire and black is the ground. Check all your connections and look at your wiring it might be shorting out the signal before it gets up to the speedo. Where the three wires plug into the back of the speedo it comes with a blue plastic retaining piece that breaks the first time you unplug the speedo. I do not think anyone ever replaces these and the remaing connector sometimes gets loose. You might want to secure it with a piece of tape. I know you are geting 12v because the 12v comes from the ignition switch and the car will not start without it. So it is probably in your wiring or in the electrical components of the speedo itself. Yours might be different than this mine is an 88. Good luck. By the way do not hook up any loose wires behind the speedo. I burned mine out in this manner. It was for an optional tach.