# 6640 Ford Gauge Cluster Problems



## jr in va (Apr 15, 2015)

My 6640 S L stopped registering the fuel level last week.Checked wires at te tank and they were still attached.Figured I'd check voltage some time and just go by the hour meter to tell when to fill up for now.

Today I noticed the hour meter had stopped turning at 6189.8 hours.I had this happen once when a faulty battery temp sensor caused a voltage drop knocking the tach,hour meter,PTO switch and diff lock all out.

My tach needle is working and so is my PTO switch.

I would appreciate any help in knowing what to check for and possibly fix before I buy a new gauge cluster I didn't need.

My display is analogue, Fuel and temp gauges plus a row of warning lights. Temperature gauge works fine.


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## somedevildawg (Jun 20, 2011)

I don't know anything about a 6640, I know it's a Ford tho, so I like em... 
first, let me say, I've never seen a battery temp sensor, don't even know why it would be necessary to have one, but I digress, I know nothing about that issue except it sounds like one of them blinker fluid deals  
But in terms of your problem, I suppose ifn it were me, or I were you, I would obviously start at the fuse block. Identifying the wires running to the cluster and maybe check continuity with an ohm meter if no voltage is present at the cluster but is at the fuse box. Could be relays, but most of those are low energy devices so I kinda doubt it....but it most certainly could be. What about an electrical schematic, have you been able to locate one on-line?


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## jr in va (Apr 15, 2015)

Thanks for the reply.Hadn't thought of a schematic.You are right,fuse block would be the first place I should start.I might also have a moisture problem causing contacts to corrode.Need to check that,too.

In regard to the temp sensor,it was an added feature to later models which now has been discontinued and the part to replace isn't available.What can be done is to make up a wiring system with a resistor to replace the sensor.New Holland dealers have a TSB which tells how.When it goes out,voltage drops and the PTO diff lock and tach all stop working.One of those ideas that seemed good but didn't work out in practice,I suppose.

All in all,the Powerstar 56,66,and 7640 tractors seemed to be good ones.Mine has been great except for a few small problems.


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