Thread: D2a TD5 - no speed signal

Originally Posted by Slunnie

Also check the Truspeed is getting power and give the potentiometers a little tweak to make sure they haven' burnt in a localised position. Likewise try the alternate speed setting incase a part of the circuit has failed that can be made redundant.

That's a good idea. I only run one set of tyres so have never used the toggle switch. I might test the other setting out.

While driving this afternoon with it all reconnected, it wasn't working. I gave the unit a tap and it worked again. I wondered if something is loose inside it but there's nothing visibly loose or rattling.

Originally Posted by twr7cx

That's a good idea. I only run one set of tyres so have never used the toggle switch. I might test the other setting out.

While driving this afternoon with it all reconnected, it wasn't working. I gave the unit a tap and it worked again. I wondered if something is loose inside it but there's nothing visibly loose or rattling.

Ahhh, I bet that's somewhere in the wiring that's not glued down and has fatigued or a dry joint.

Is it worth the risk to try and remove some of the potting (black gunk) around where the wires go into the circuit board, maybe there's a dicky joint there. Sharp Stanley blade and a bit of patience... And a few brews...

Hi the black gunk is low temp tar or a silicone mix ,,,( for water proofing )
If its lo temp tar (you can smell it )
A hair dryer will let it drip out on heat setting ,,, you will find its most likely the transistor on the top left could also be one of the multy turn VR ( the blue plastic resistors )

If you like i can test the TR and VR`s for you ,,,, ?

So, did some testing. With the top off, if I push down on the yellow wire, the speedo works again.
I cut open the back. Got lucky that the black stuff either hadn't been applied properly or didn't stick well in this area.
The joints looked a bit dry, redid two of them, sadly not the fix. Removed the yellow wire and made up a new one - still didn't solve it. I think there must be something wrong further along, perhaps a crack in the board or something.

I've given up now and ordered a C1600 Ratio Interface Unit from Hunter Di Spare Parts Company.

Originally Posted by rob tilbury

Hi the black gunk is low temp tar or a silicone mix ,,,( for water proofing )
If its lo temp tar (you can smell it )
A hair dryer will let it drip out on heat setting

Sorry, forgot to mention that I tried this with a heat gun. Even on full heat it wasn't melting at all. It's hard like plastic when cold and still hard like plastic when hot (it was far too hot to touch for more than a split second) after being heated.

I'm having the same problem, haven't opened the truespeed yet will see how I go, might try the toggle switch too, could be another for a c1600-4

Interestingly enough, two years later, with a fully functional C1600 Ratio Interface Unit from Hunter Di Spare Parts Company I'm getting the error again - "(22,1) ROAD SPEED MISSING, (LOGGED)."

Doesn't seem to be having a negative effect on the vehicles operation though.