I just got the new 454 HO engine going in the Barth after sitting for almost 2 years .
After driving about 10 to 15 miles the speedometer started acting crazy .
The speedo needle goes 360 (in a circle) the whole way around. The faster the coach goes, the faster the needle goes around in a circle . when the coach stops the needle stops .
I think the odometer still works, I will verify this for sure tomorrow .

1) Can anyone shed some light on this problem ?
2) Or explain how the speedo works, I know nothing about speedometers .

Thanks , Bob

The speedo is driven by a cable which leaves the transmission, goes to the cruise control, then another cable to the speedo itself. The rotary motion of the cable drives a magnetic cup in the speedo. Next to the cup, but not usually touching it, is a lever attached to the needle. The needle is spring loaded to make it return to zero. The faster the cup turns, the more magnetic force to turn the needle higher against the force of the spring.

It appears that the spacing between the cup and needle is too close and the needle is hooking up to the cup and spinning with it.

Your speedo needs work! Hopefully it is not trashed.

If you can't get it to work I have one you can have. It also needs work but it isn't trashed. It reads slow when cold then gets faster as it warms up. Rather than service it I replaced it with a cool GPS speedo from SpeedHut. (It probably matches your dash too since our coaches are same age.) Let me know if you want my old one.

I think your speedo is just reacting to your new 454HO… It KNOWS how fast you could go now!

Keep us posted, good luck.

Steve, Maybe a pacemaker would calm the speedo down or shock it back to normal.

Can I take the speedo apart , so i can clean it or adjust the needle & cup ?

Or are they a sealed unit ?

Thanks, Bob

Sounds like Steve is on the right track. Also check the cable for sharp bends, or internal dryness. This can cause the cable insert to twist and spring back, causing needle bounce. You may need a new cable insert . Now this is only if yours has a speedo cable. If it has a speed sensor, this doesn't apply. You may be able to take the unit apart to clean it and check for internal dragging. Good luck.
Phil

I don't think they are made to take apart but I'm sure you can do it some how yourself. My old one is downstate so I can't look at it easily…

Not much to them. The old ones had the cable turn an input shaft with the magnet on it. The needle was on a separate shaft with a spiral return spring. You could slide the input shaft in closer or out to make the needle read higher or lower.

I'm not sure the new ones are considered adjustable…

There may be too much axial play in the input shaft bearing. Or as Phil suggests, there may be a cable problem. If the cable binds it may ride on the shaft and push it in too far.

Press on, if you break yours (worse than now!) you can swap/cannibalize mine.