daf 45-150 7.5t speedo

[taylorm840]

help please

while trying to sort one problem ive now caused another.

i removed the fuse for the tacho, there was an arcing but the fuse has not blown, the speed needle moved to full speed, on opening the tacho it went back to zero but the over speed warning light is now constantly on and the speedo speed needle now does not work.

any ideas on a fix ?

[bigwheel]

Disconnect the battery with the Tacho head open. That'll let the speedo mechanical drive reset behind the Tacho head.
Hopefully the red light will stay off.

[megenzo]

the full scale deflection of the speed needle is because you have caused a break in the speed trace signal. Put the fuse back in ad if it still does it you'll need to resolve the arcing problem as that will also cause a fault to be recorded, the tacho thinks you are trying to fiddle it by stopping the speed trace supply so it needs to be fixed to get it to work properly. Plus if there is an arcing issue it could start a fire.

[AF1]

Also in some of the older 1318 heads you sometimes need to insert some cards to get the speedo working again.

[megenzo]

Good point AF1, take a picture of the tacho head unit so we can see what model it is, we may be able to narrow down the fault as it will be a diagnostic. Have you put a test chart in it?