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WEIRD SPEEDO/TACH PROBLEM

August 01, 2012, 02:47:13 pm

My speedometer and tachometer are acting strangely.
When I start the engine after the coach has been sitting for a while, the tachometer will not function at all. Later in the day, it will come back to life. I find that it only does this east of the Mississippi.  After it comes back to life it will work just fine until the next time the coach sits for a while maybe a day, maybe a week.
The speedometer/Odometer is doing similar things. The odometer will occasionally work and record mileage, mostly NOT.  The speedometer will usually work after running for a while like the tachometer. 
I am assuming a bad ground or a corroded or loose connection.
It would seem that the sensors on the engine/driveline would be suspect and I have NO idea where to locate these sensor connections.  I hope someone on the forum has dealt with this problem previously.
I will attempt to check, clean and lubricate all of the connections that I can find under the instrument panel.
I was also wondering if an ignition switch connection might be at fault.
Anyone run into this situation?  Did you cure it? Please advise as to how.
Comments?

Regards,

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Re: WEIRD SPEEDO/TACH PROBLEM

Reply #1 – August 01, 2012, 03:02:46 pm

My speedometer was acting similarly to yours and I had to replace it. It has been working fine ever since. It is the third speedometer for this coach.

Mark Z

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Reply #2 – August 01, 2012, 03:53:24 pm

Jon,
I've had similar symptoms in the past.  I would clean the contacts as you describe and make sure the voltage is good.  It seems low voltage makes these instruments go bonkers.  My problems went away once the voltage was high and the all ground contacts were cleaned.  My instruments were replaced back in 2003 when I purchased the coach, and even the new speedo & tach have acted up since replacement.
Peter

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Reply #3 – August 01, 2012, 04:34:05 pm

easy fix then, stay west of Missis'!!!
John

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Reply #4 – August 01, 2012, 08:29:58 pm

Regarding staying west of Mississippi, I would if I could.
Still have property in Michigan that I have been unable to unload due to "everything".
So, must come back and maintain it.
Regards,

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Re: WEIRD SPEEDO/TACH PROBLEM

Reply #5 – August 01, 2012, 10:38:52 pm

Jon,

If both are acting up it could be ground problem. Run a temp wire from ground to both meters. Our meters have ground, ignition connection on bottom row. And sensor wire on top row.

Our tach sensor is a pickup on the engine bell housing, accessible from under bed looking straight down. Our sensor had a poor wire connection that was easy to fix. Spedo sensor probably comes from Allison transmission cable bundle.

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Reply #6 – August 02, 2012, 08:06:46 am

Hope the other's are right about ground or loose connection. 

But on my older 1993 U-225, the speedo and tack were the first things to go haywire when my ignition solenoid was going bad.  Lost them, and then other things, off and on, till I replaced with a new one.  Then that one lasted 6 months, till I upgraded to the Blue Sea unit, since then all is well.

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