Instrument Cluster Circuit Board Problem

[Seanhoya]

Gents,

 

Most of you who have been following the Vintage Mooney Forum have seen my posts now and again, and some of you might have looked up my profile and realized that I have been in Haiti for the last year.  Well, I am going home, and my mechanic is doing my annual on my 1968 M20G which has been sitting for a year.

 

He emailed me this morning to let me know that there is a problem with the analog gauges (I don't know which ones yet - I assume all).  He said that whenever he turns on the Master power, the gauges all peg, and stick there.  He says that he has trouble-shot the problem, and the problem lies in the Instrument cluster circuit board.  He is having problems finding someone who works on this Weston part (frankly, I am not familiar with it).

 

I think that I have had this problem before with individual analog gauges - I think that it was a short somewhere in the system.  But I trust his trouble-shooting, and I would appreciate any advice on whether to buy an aftermarket part (if one exists), or other courses of action.  I have replaced my CHT gauge with an aftermarket Aerospace Logic 200 series sensor, but otherwise, all of the other analog gauges remain operational (or for the moment, not operational).

 

Thanks,

Sean

 

 

[DS1980]

Before anyone responds, thank you for your service.

[N601RX]

My 67F uses 6 individual gauges that plug into the 6-pack cluster. If yours uses the same setup, I would suspect a loose ground if they are all pegging when turned on.

[Seanhoya]

Gents,

 

Thanks for your support - a little more amplifying information:

 

1.  Yes - it is the 6-pack cluster.  My mechanic has run a new ground twice, consulted the mechanic's manual (the Lasar aftermarket one), and found a couple of peculiarities:

 

A.  The Amp meter is working fine and apparently is grounded to the Starter Solonoid - it is the only one of six instruments which is grounded in this way.

B.  The fuel gauges are supposed to have their own ground (according to the manual), but they don't.  They peg, and then settle somewhere above empty after the power is turned off.

C.  The oil temp gauge pegs, then settles around 50 -80 degrees.

 

I had a similar problem before with the CHT sensor, and decided to replace it with a Aerospace Logic 4-probe CHT sensor.  My mechanic is concerned that one of the resistors on the circuit board behind the 6-pack is fried, so he wants to have someone look at it.  Any recommendations out there?

 

V/R,

 

Sean

[carusoam]

Chances are you'll find the ground or missing ground to solve the problem...

If you don't, there are replacements available that have been posted here somewhere....

Unfortunately I don't recall who posted it under what title...

Good luck and best regards,

-a-

[scottfromiowa]

I believe SabreMech did replacement.

[lamont337]

Was SabreMech the one who posted this: http://www.mitchellproducts.com/modular.htm ?

 

Bookmarked it a long time ago but don't remember who provided...

[takair]

Sean

I agree with the folks above. Sounds like a ground problem. The circuits are essentially isolated within the cluster with the possible exception of the ground. It may be worth checking the connection at the fuel senders too. I am not aware of anybody who works on the cluster, but used ones appear on ebay and Barnstormers from time to time.

What happens with oil temp when he runs it?

[Seanhoya]

Gents,

 

An update - oil pressure works fine, it is oil temp and right and left fuel which all peg.  I am sending the unit to Keystone Instruments in Pennsylvania to see what they can do with it.  Will let you know how it turns out.

 

Sean