KAMA Instrument cluster

[Paddy]

As you may have deduced, I'm doing some maintainance on my KAMA 454. got the oils changed and now going for some other small issues.

On the instrument cluster all works except for the Tach and fuel gage. I cleaned the 3 plugs under the dash. Tighened the screws on top of fuel tank sensor leads. With key on, measures 7.7 Vdc. Then hooked a wire and raised the fuel sensor float, no change in voltage.

The tach sensor at flywheel measured 1.7 VAC at idle. Gental bangs to the back of the tach, cluster, and she came to life for 5 sec. Repeated and it was still working for a few min before shutting down. Hour meter has always worked

Ideas?

Patrick T

 

[Rich Waugh]

I'd guess either bad ground(s) or possibly bad solder joints on the circuit board. You'll need to take the cluster out where you can really see it with a magnifying glass and check it thoroughly, re-soldering any suspicious-looking connections and cleaning the board to be sure there isn't any debris bridging contact points.

 

[greg_g]

I'm almost certain that the KM454 hour meter uses tach voltage as it's trigger. That strongly suggests that your tach sending unit down at the flywheel is probably ok. But it's still a good idea to take it out and inspect the sensor tip for damage. Lacking that, I'd say the issue is all instrument cluster. Plus, your cluster is not shock mounted - and vibration is hard on printed circuits.

So the question becomes; have you physically removed the cluster from the tractor yet? and given the back side a close visual inspection?.

//greg//

 

[Affordable]

If you cannot find any loose connections ,you will prob. have to just replace the panel ,I have them in stock if you need one,they make several different ones so a pic is helpful

Let me know if we can help

Tommy
Affordable Tractor Sales
"Your Jinma Parts Superstore"
Home of compact Jinma, Foton, and Koyker Tractors and Parts, Wood Chippers, Backhoes - Affordable Tractor Sales Company

 

[greg_g]

Patrick, I've been holding my cluster and multi-meter ready for several days now. My intention was to help you through this with a little one on one. Let me know if you've gone in a different direction, and I'll put this stuff away

//greg//

 

[Paddy]

greg,

sorry, been out. I've looked the back over and it looks fine to me. for printed circuit boards, these have wide solder paths between spots of connections. Did the voltages I gave above appear normal?

 

[greg_g]

"Normal" is relative in gauge circuits. The battery provides a nominal 12v supply, and the sending unit typically varies the resistance to ground. No resistance means the full 12v goes to ground, max reading on the gauge. Full resistance means no voltage gets to ground, no reading on the gauge. Voltages in between 0 and 12 are what move the gauge between extremes. So if you consider that voltage at the fuel sensor is related to the level of fuel in the tank, 7.7 volts would suggest about 2/3 tank. If true, than 7.7v is "normal". Using the same logic with the flywheel sensor, 1.7 volts (DC) would suggest the tractor was off or idling when measured. If true, then that too might be considered normal.

But let's revisit the printed circuit. You need to inspect it under a bright light with a magnifying glass. The traces on the board represent ground. Any hint of discoloration (usually brown) indicates a short on the REVERSE side of the board. Next inspect solder points in the trace. On this board, they also represent ground, as do any wires that may be soldered to them. Vibration causes solder to separate from trace. A solder point that's cracked (partially connected to the trace) can be responsible for intermittent action, like when you banged on the cluster and got it to work briefly. A solder joint that's broken (fully separated from the trace) causes an open - or dead - circuit.

Traces can be repaired. But the way this board is attached, it would be difficult (if not impossible) to safely remove the board for repairs to the back side. Puts you pretty much in the position of buying a new cluster. But bad solder joints on the visible side are repairable. I found a couple of bad solder joints on a $175 circuit associated with the automatic climate control on my old Mercedes; damaged by years of vibrating alongside a diesel engine on aging motor mounts. Fortunately the loose solder joints were easily accessible. Got my ACC fixed for $5 worth of solder repair, instead of having to buy the whole $175 part.

//greg//