Fogging Tachometer / Hour Meter

After running for just a few minutes today the Tachometer/Hour meter suddenly fogged up and I could barely determine the RPM to an approximation. After a bit longer the fog turned to droplets that obscured the meter even worsel This is a first after a couple of years of operation of the tractor by me.. The tractor resides in a shed (repuroosed car port) I just recently washed off a heavy accumulation of dust which is probably the source of the moisture.

How should i go about dealing with this?

1, How important is it to dry out the meter and how is water removal done.
2. How does one seal the unit to prevent further occurances?.
3. Is the unit even supposed to be sealed, or is it supposed to be vented.
4. Is the leak source likely to be along the flexible shaft which drives the instrument rather than around the lens.

The instrument appears to be totally mechanical Lacking even a light

If It must be dried out, I would propose to seal it in a container and draw a vacuum on it.

That might be accomplished with something as simple as a plastic bag, provided that will not crush it, pop the lens off of it or otherwise damage it.. If not that then enclose it in something rigged from plastic pipe for a vacuum chamber or Just bag it along with with a bag of dessicant.

Suggestions and comments please.

Welcome to YT.
It would help if you'd state what brand & model tractor you're referring to.

I suggest to remove speed/hr meter and put it in a bag of while uncooked(raw) rice to see if moisture will relocate to the rice.

I agree and if you can do the vacuum trick that is a good thing. I wouldn't heat it but if you can pull 39 inches like with an AC pump. I have pulled a couple of Amp gauges apart and resealed them with a little silicone around the inside of the ring. You need a tiny little straight blade screw driver and work your way around the under side of the bezel ring slow and gentle. Lift up the metal a little at a time and keep going around and round so as not to stretch the metal. You will finally be able to get the ring and glass lense off and then let the gauge sit in the hot sun for a few days to dry out. The seal around the bezel ring and glass is no good. To put it back together you need a tiny bit of silicone and you want enough so it scweezes or squissshes out a little. When it has cured for a day or two, then use a razor to trim it. I use a special pair of parallel pliers and gently nibble my way around till done. Take your time and pinch it JUUuuuussssttt enough! Let us know and have fun.

If he can draw 39 inches (Hg) of vacuum he can make enough on the lecture circuit to by SEVERAL new tachs!

Probably if you just run the tractor and get it good and hot the tachometer will dry out from the heat. It's not real critical to be able to see the tachometer and hour meter.

Yeah that's exactly what I thought! If you got a way to draw 39" vacuum then park the tractor and go get into some kinda super fuzzy science field! People been trying that for decades!

Go to your local junk / second hand / thrift store and buy an old hair dryer, the kind that has a plastic hose connected to a bag helmet. They dont get hot enough to melt / burn anything, but an hours flow of 120 degree hot air over the unit will dry it out right on the tractor without removing anything.Aim the heat at the back side of the thing.
Also is a very handy unit for drying out wet ignition systems

You need to find a real problem to obsess about. Sure you could seal the face but you could never seal the back. Water vapor will get in when humidity is high and condense on the back of the glass when the temperature drops. When the humidity drops all of the moisture will be sucked out by the surrounding air without you lifting a finger.

Showcrop,you need to shut-up and quit belittling people......may god help you

Well it is a real problem to him if he wants to see his tach. Skip the negativity.

(quoted from post at 13:03:06 10/14/15)
You need to find a real problem to obsess about. .

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ll,cut you some slack showcrop, I can sound like a bit of a curmudgeon[b:57a3155d6c][color=darkblue:57a3155d6c][1][/color:57a3155d6c][/b:57a3155d6c] sometimes myself. I was trying to assess how much of problem the matter might be. Your answer did address my query in the original post "How important is it to dry out the meter" No offense taken. My objective is to maintain the meter in an operable and readable condition. I have seen tractors with instruments so damaged by water as to be unreadable even though the needle still moved.

Sure you could seal the face but you could never seal the back......

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ctually I might be able to. The tractor is a ford 1510 made by Shubaru. A lot of those oriental tractors are made with rice paddies in mind and I know the Japanese put in the most sophisticated front wheel grease seals I have ever seen on a land vehicle, so they might have exercised a bit more water tight integrity than is customary. My use of the tractor is sufficiently intermittent that I doubt my ability to control the speed just by ear.

This tach/hr meter is driven by a flexible shaft (e.g. speedometer cable) which enters through a "can" which is held by a clamp that pushes against the back side of the instrument panel. It appears to be able to be a "sealed" unit, and the only leakage paths would be around the lens, bezel, or shaft. The moisture could have come from inside the engine via the shaft housing. So the sealing of the lens/bezel plus re-greasing the shaft might just do the trick.

if you can pull 39 inches like with an AC pump.

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hat's Ok, I have been razzed for "fat finger typos" for things like the zero key being right next to the nine key.:wink:

[b:57a3155d6c][color=darkblue:57a3155d6c][1][/color:57a3155d6c][/b:57a3155d6c]
From http://dictionary.reference.com/browse/curmudgeon?s=t
[b:57a3155d6c]curmudgeon[/b:57a3155d6c]
1.
a bad-tempered, difficult, cantankerous person.
Synonyms
grouch, crank, bear, sourpuss, crosspatch.

[if it is truly a sealed unit I would drill a small hole in the bottom and mother nature wil balance out the moisture.

If it has a light on the bottom, turn it on to heat up the container or tach.. It will dry it out.

If not, maybe look to see if a hole and plug are on it for a light.


If not put a old fashion trouble light near it and leave a 60 watt bulb on, for the heat for a couple of days. It should dry it out...


But severe temp changes and high humidity will always be a problem. Any surface that cools quicker will make the water condense out to the warmer surface. The metal will cool faster than the glass. I am lucky and just run the lights and dry my gauges out.

(quoted from post at 18:12:06 10/16/15) [if it is truly a sealed unit I would drill a small hole in the bottom and mother nature wil balance out the moisture.

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hanks for the suggestion. I think I may use a variation of it. I have made a vacuum chamber out of 3" PVC pipe and a little experimentation with my compressed air driven Bernoulli effect vacuum pump draws a vacuum so quickly I was afraid that it might pop out the lens. However a small vent hole would allow rapid equalization of the pressure on the unit. The hole can be easily sealed with epoxy after the unit is dried out or a small screw inserted with sealant. I will try to get some pictures but I cannot get back to the project until Saturday evening.

For the record the Tach/hour meter is a permanently assembled unit. The body is a "can" with an open end at the lens end and a hole at back end where bearing housing sticks out to allow the attachment of the flexible drive shaft. Apparently the mechanism is inserted through the open end and then the bezel which holds the lens it crimped on and forms part of a flange. The unit is installed by inserting it into the instrument panel from the operator's side, and then a bracket on the back side of the panel is bolted on to hold it into the panel.

Where the bearing housing comes through the back of the housing "can" a generous amount of some green sealant has been applied. So apparently it is intended to be a sealed unit. I may consider using a hot glue gun to seal the lens and the bezel so that I do not have to wait for silicone to dry and also to seal any vent hole I drill.

I decided to go ahead and clean and re-grease the flexible shaft and while removing it from the side of the engine (it is driven at the front of the engine) I saw a small piece of something fall on the shop floor. I thought it was a tiny rubber plug but when I picked it up it turned out to be a tiny magnet. It is surprisingly strong it is cylindrical a and measures 5mm in diameter by 5 mm long (5mm = 0.197 " or about 3/16"). Careful examination of the shaft and the instrument indicates it is not part of them and was probably something hanging on the wiring support bracket that holds the flex shaft housing. I have no idea what it might belong to, and just for the record I did verify the the shaft & meter assembly function properly and are missing no parts. So if anyone has an idea what this mystery magnet is please share.

At lens diameter of 2 inches if I could get a perfect vacuum, 1 atmosphere of pressure would be 14.7 psi times an area of 3.14 square inches or 46 lbs of force so fracturing or popping the lens out if I do not vent the can is a real possibility.

Ok so I sort of promised you some pictures.
This is the tachometer/Hour-meter unit. It is 2 inches in diameter.

As mentioned previously I decided to go with putting in a vent hole to prevent the vacuum from damaging the unit. To do that I wanted to be careful not to damage the insides and since it is a permanently sealed unit I decided to be careful so I did it like this:

Ok it looks a bit like overkill but this way I could mill into the housing 0.005 at a time and be pretty sure I was not going to damage something internal.
This way I was able to make a vent hole just where I wanted it. The results look like this.


Next was the water removal in my vacuum chamber that I made.

I put the Tach/Hr-Meter in the chamber and drew a vacuum. As I drew down the vacuum I suddenly could hear the water hitting the Bernouli effect venturi When I pegged the meter at 24 inches of vacuum (It may have been even more than the gage could indicate) I pinched the hose with the vice grip pliers. A half hour later I came back and had not lost any vacuum. I vented the system and hammered the end cap off. The assembly had given up some of its water and was cold. I figured that drawing the vacuum had a refrigerating effect which caused partial water retention. So I set the assembly in front of an electric space heater and in 5 minutes it was getting too hot to handle. I repeated the vacuum process and this time I really heard the water coming out. (a sort of muffled slurping sound after the vacuum was getting down part way). I let it draw down the vacuum until the slurping stopped and then it pegged the meter again. I pinched the hose and left it for an hour this time. Again no vacuum loss. I vented the system and opened it up and the result was completely satisfying. No water at all could be seen any more behind the lens. Both droplets and fogging had cleared. I closed the vent hole with a piece of vinyl electrical tape. I then sealed around the lens edge of the bezel and the case edge of the bezel with clear silicone.

I plan to reinstall it tomorrow and see how it all holds up. If it ever need to be dried again, All I have to do is pull off the tape and repeat the process. Time will tell but I think I have a useful tool here.

Well I got the tachometer / hour meter reinstalled no thanks to the tractor being designed to accommodate small Japanese hands. Getting a US standard size hand between the fuel tank and Instrument panel while holding a tiny nut and tiny lock washer and trying to put it on a threaded stud without dropping and losing a part is no fun. Just getting both fasteners together too about 15 minutes of careful fiddling braille style. Access is also so awkward as to make judging torque on those nuts too difficult. I settled for "probably tight enough" and then used some penetrating grade screw sealant, and a long thin screw driver to apply it; to make sure they did not fall off due to vibration in a year or two. Nevertheless. the unit now works and the lens is brilliantly clear.
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But speaking of small Japanese hands, I was wondering if other owners of Japanese tractors may have the same problem that I have. While I cannot fault the generally high quality of the workmanship on this tractor, this is not the first time I have suspected that the design may not accommodate average American male body size as well as it might.

I have noticed that while dismounting the tractor that my left foot is somewhat entrapped, between the transmission housing, the clutch pedal and the fender. To dismount without risk of injuring my foot, the routine is as follows.
-- Stand up on the foot plates.
-- Place right foot atop the transmission housing.
-- Pivot on right foot while....
-- Lifting left foot from between pedal, transmission and fender.
-- Swing left foot backwards.
-- Lower left foot below clutch pedal.
-- Reinsert left toe under clutch pedal onto the foot plate .
-- Move the right toe to the left side of the transmission housing top.
-- Grab the steering wheel on the left and fender mounted assist handle on the right.
-- Lower right foot to the ground as you back off of the tractor.
-- Remove left foot from foot plate and set on ground.

At first I tried going off the tractor forwards as I remember doing on the Ford 8N that I learned to drive on. I can do that with this small tractor, but I find my arms being pulled far enough behind me so as to hurt my shoulders and my left foot did not always cleanly disengage from its entrapment. This caused me to develop the above scenario in order to avoid wrenching my shoulder or doing a face plant due to tripping over the clutch pedal. My foot is just too big to escape through the gap between the clutch pedal and the fender reliably and unless I get it outboard of the clutch pedal there is just not enough room on the foot plate to pivot on it. I am only 5'11" and know quite a few guys and a woman or two who are significantly larger.

And while I am complaining about a few other features of this otherwise well designed and built tractor:----------

The first deficiency I felt compelled to correct was that there was no provision for a tool box. Since I do not have a front end loader and no plans to acquire one, nor an under belly implement. I used the mounting holes in the side of the tractor along with some angle iron, machining and welding to come up with a way to mount an "ammo can" conveniently and mostly out of the way in a sturdy fashion, as shown here:


Now if I need to perform field maintenance at the back of the property I do not have a long walk for basic tools. I am wondering if small Japnese farms such as might use a tractor of this size are small enough that they do not regard field maintenance as occurring far enough from home to justify a toolbox such as this.

But for all my nit picking, I do regard this as a very worthwhile tractor. The fuel efficiency seems to be fabulous!