MF35 diesel ignition switch

jetmech53 · Jan 20, 2015

I purchased a Tisco 883928M91 replacement switch. When I check it electrically, what I see as the "heat" position is also energized in the start position.
My understanding of diesels is that heat is not required after the engine is warm or has recently been running.
1) Is this the correct switch? Correct switch operation?
2) Will it "really" matter if the heat is on during a warm start?

I have an electrical print for the tractor, however it doesn't help with the internals or operation.
1963 MF 35 perkins diesel.

DavidP, South Wales · Jan 20, 2015

Hi,
Originally the (UK) switches hhad two directions of operation. In one direction the key was turned straight to the start position. In the other it went to heat and then start. Later switches are Off/'ignition'/heat/start. If the only way that it can be wired is to have the heater operating it should not cause any problem as ideally the starter will only be operating for a very brief period..

DavidP, South Wales

jetmech53 · Jan 20, 2015

(quoted from post at 06:02:22 01/20/15) Hi,
Originally the (UK) switches hhad two directions of operation. In one direction the key was turned straight to the start position. In the other it went to heat and then start. Later switches are Off/'ignition'/heat/start. If the only way that it can be wired is to have the heater operating it should not cause any problem as ideally the starter will only be operating for a very brief period..

DavidP, South Wales

The switch goes left for heat and right for start with a spring back to neutral as the placard indicates. I alway thought the glow plugs should NOT operate with a warm/hot engine. I guess it doesn't hurt for it to operate during the start even if the engine is warm. Yes??
Thanks
BTW the placard has "H S" beyond the heat position. Neither switch goes that far, but was does it stand for? Hydraulic system?

ptfarmer · Jan 21, 2015

It won't hurt the glow plugs to be on for a few seconds when the engine is already warm.

Dieseltech · Jan 21, 2015

H-S was on some for heat-start. My Standard diesel has off position, right is start, first left is heat, second left is heat-start. Mine starts best after 15 seconds of heating the Thermostart. C.A.V. service letter shows the heating coil will be damaged IF used for more than one minute, or no fuel is present at the inlet of the thermostart unit. There are three fuel rates of the thermostart units too, low, medium and high. My TO 35 will flood if used too long, but my MF 85 will not as it has a lower flow unit than my 35 does. Not sure why they came like that.

MF35 diesel ignition switch

jetmech53

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DavidP, South Wales

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ptfarmer

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