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(Another ) Answer to a question no one asked. Warning light DIY

#1

M

motoman

I have looked into ways to add a dashboard overheat warning light. This is for air cooled tractor heads. Any interest?:anyone:


#2

D

dodgefate

I would be, as I often use my tractor to pull boats and have a front end loader attachment on it and it puts a strain on the motor. DOnt know what the high temp warning should be, But I have seen some on older 2 stroke boat motors that sit on the head....


#3

M

motoman

dodgefate said:
I would be, as I often use my tractor to pull boats and have a front end loader attachment on it and it puts a strain on the motor. DOnt know what the high temp warning should be, But I have seen some on older 2 stroke boat motors that sit on the head....
Click to expand...

OK, I put the stuff away. Whenever DIY is stated I do it to my tractor first, but have not installed the warning lite yet. Just a reminder my machine is a Craftsman DYT 4000 B&S 24. As stated this probably only makes sense for air cooled tractors.

One thing I would like to redefine: Such a warning lite is not an "idiot" lite, rather a "smart" lite since it can alert the owner to temperatures which IMO are detrimental to aluminum castings: 325F to 350F as a warning zone before hitting the dreaded 390F zone where aluminum starts changing.

Patience while I pull the stuff together. :tractor:


#4

M

motoman

ANSWER...DIY WARNING LITE
The writer experiments only on his ride around tractor which has alternator/battery 12 v system. Readers should comment about smaller units which could power warning lites . For instance could a magneto current (already weak by automotive standards) power an LED warning light?

SWITCH TYPES Best choice may be the "thermostat" type with bimetallic contact. These open or close at a specified temperature.

SWITCH "NO' Normally open contact (at room temp). They close at a given temp, and can pass current from tractor ignition (magneto?) to a warning lite, or they can provide ground. The "NO" thermostat switch is also known as " close on rise." This switch is ideal due to its simple wiring. Unfortunately, retail availability of the 325-350F units seems limited and the one shown here is larger than desired.

SWITCH 'NC' Normally closed (at room temp). They open at a given temp. These are available retail with many temp settings in the 300-370F range, and many are smaller. Unfortunately the on-off logic is backwards for the tractor warning lite since we want a lite to go on when the tractor head is too hot. These "NC" style switches are also known as "open on rise." Discussion below on how to use this type switch

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#5

M

motoman

ANSWER...DIY WARN LITE

"NC" SWITCH WITH RELAY What to do with "murphy's law" working against simplicity? An "SPDT"
(single pole dual throw) relay can be used with the NC style switch for our purpose. (Do not turn away because of this. The relay is simple and small, about 1-1/2" cube, and can be bought with a mounting bracket). The 5 pin (or blade) automotive relay is common and cheap. After the relay is wired the "NC" contact is ignored, but when the switch is opened at high temp (350F, for instance) the relay transfers 12V to the tractor (or lawn mower) "dash" warning lite.

In case schematics bore you ....pictures below of the two switches wired. Remember the NO style can easily be wired to provide ground for the lite with even less wiring.

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#6

M

motoman

ANSWER...DIY WARN LITE

SWITCH PLACEMENT Your engine may have different head finning areas. IMO the proper placement is near the exhaust valve guide (photo of smaller, NC switch). If only the larger NO switch is available go with 325F where it fits. Seems like extension plates bolted on might fail due to vibration.

SWITCH RESET The thermostats actuate at a specified temp + or - 12-15 F. But automatic reset is considerably below so the dash light will stay on until that lower temp is reached , then switched to its room setting. There is at least one switch with manual reset, SELCO button 70098769 320F NC style $10.

FASTENERS, STRESS, CORROSION

Locktite red is good to 300F. Nyloc nut inserts melt at 250F. This leaves "split beam" or "deformed head" lock nuts as the alternatives. Unfortunately, in 4-40 and 6-32 these are "aerospace" type and very expensive. Aluminum pop rivets might work if the gun head fits the tight quarters. The fastener holes must be oversize to allow the head material to push the fasteners around. Note the slots on the big switch. Debur the drilled holes. No over torque. No lock washers which would gouge or scratch the aluminum. The environment should be mostly dry, helping somewhat. The switches shown are stainless or plated. Thermal grease is available for dissimilar metals.


#7

M

motoman

ANSWER...WARN LITE DIY

SOURCES The NO (large) switch shown (tested good) is from SENASYS, # 2511F036-325F-168, online $10. The NC switch is ref only as it failed bench test-wrong temp. It is surplus, but is representative of the small syle. Some brands not readily available retail are : KLIXON, COMSTAT 3451RC, 2450/55 series. AIRPAX 5003. Best bet is Allied Electronics which offers a range of switches and relays on line, $6-$10. :cool:


#8

M

motoman

Well, not tried but in fussing with the Xmas tree led's I was reminded of how little current it takes to turn on and light one. Seems like a dash or bracket (smaller lawnmower) led would work once the proper resistor was placed in line. The LEDs only want milli-amps. What would be wrong with a flashing red led if you had no battery? Another question no one asked. :laughing:


#9

M

motoman

Today I accidentally ran into some Kohler factory "hi temp cutout kits" which are for 346-495F temperatures on several different models. The pictures were weak, but looked like switch control from the exhaust valve area of the head. One kit talked about cutting cyl head fin for clearance. Prices $77 to $131. Reinventing the wheel here?

So this thread is not something new but with a warning light . Cut- out wiring would not be hard. I think this thread is cheaper at $20-$40. :laughing:


#10

M

motoman

motoman said:
ANSWER...DIY WARN LITE

SWITCH PLACEMENT Your engine may have different head finning areas. IMO the proper placement is near the exhaust valve guide (photo of smaller, NC switch). If only the larger NO switch is available go with 325F where it fits. Seems like extension plates bolted on might fail due to vibration.

SWITCH RESET The thermostats actuate at a specified temp + or - 12-15 F. But automatic reset is considerably below so the dash light will stay on until that lower temp is reached , then switched to its room setting. There is at least one switch with manual reset, SELCO button 70098769 320F NC style $10.

FASTENERS, STRESS, CORROSION

Locktite red is good to 300F. Nyloc nut inserts melt at 250F. This leaves "split beam" or "deformed head" lock nuts as the alternatives. Unfortunately, in 4-40 and 6-32 these are "aerospace" type and very expensive. Aluminum pop rivets might work if the gun head fits the tight quarters. The fastener holes must be oversize to allow the head material to push the fasteners around. Note the slots on the big switch. Debur the drilled holes. No over torque. No lock washers which would gouge or scratch the aluminum. The environment should be mostly dry, helping somewhat. The switches shown are stainless or plated. Thermal grease is available for dissimilar metals.
Click to expand...


Edit 2-15-13 FASTENER UPDATE For those few of you interested I found a source for the 4-40 and 6-32 all metal, self locking nuts , good to 450F. Go to pegasusautoracing.com and see MS21042-04 and MS21042-06 . You can buy small quantities without breaking the bank.


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