Regarding "Thermostart" wiring!

   / Regarding "Thermostart" wiring! #1  

Arber

New member
Joined
Nov 16, 2025
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10
Tractor
Ford 3000 2.9L Diesel 1968 10 Speed. Made in England
Hey everyone my Ford tractor has a thermostart feature and I don't know where to wire it, wiring it directly to the ignition switch like on Massey Ferguson tractors wouldn't work since this particular ignition switch only has three modes OFF/ignition ON/Start, normally you'd want the switch to be a momentary or like I said on Massey tractors where it is spring loaded halfway. I'm not sure if Ford intended to use a stand alone momentary switch or? (If you do know of such thermostart switch please post the part number)
The ignition switch is original for this tractor!
Should I' replace the switch with one from a Massey Ferguson so that I can use the thermostart feature?
Thanks.
 
   / Regarding "Thermostart" wiring! #2  
You have the original switch, C5NN11N572A r/b 82849165 which was 3 terminal for tractors without thermostart.

For thermostart, you need 4 terminal switch, E7NN11N501AC r/b 82849085 Switch Assy., Heater Starter, Diesel W/Cold Start.
Aftermarket $14 to 26. It will have OFF/Ignition ON/Start/Start + thermostart

Same key
 

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   / Regarding "Thermostart" wiring!
  • Thread Starter
#3  
You have the original switch, C5NN11N572A r/b 82849165 which was 3 terminal for tractors without thermostart.

For thermostart, you need 4 terminal switch, E7NN11N501AC r/b 82849085 Switch Assy., Heater Starter, Diesel W/Cold Start.
Aftermarket $14 to 26. It will have OFF/Ignition ON/Start/Start + thermostart

The part numbers you mentioned all refer to the same ignition switch where the only difference is the 🔑 shape, my ignition switch looks exactly like the ones you mentioned with 5 terminals and only three positions. What I'm trying to say is there must be a pull type of switch like a choke. On the website It does mention the ignition switch has the thermostart option but you do need a four position switch for that not three! My guess would be Ford reused their old stock of ignition switches from their older gasoline models and they simply added a small momentary pull lever switch for the thermostar but I could be wrong.

Edit: You mentioned the "Off/Ignition ON/Start+Thermostart"
There lies the problem, thermostart needs to be ON for at least one minute before you start cranking!
Looks like I will be replacing the ignition with one from a Massey Ferguson 135, what an awful design choice by Ford 🤢👍.
 
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   / Regarding "Thermostart" wiring! #4  
Both switches use the spade key.
Pictures show the configuration of the diesel/thermostart switch. Position 5 is start + thermostart
Here is the operation (Clockwise/Right):
1- Off: Key out position.
2- Accessories (Acc): Powers lights, radio, etc..
3- Ignition (Run): Powers the engine systems.
4- Pre-Heat (Thermostart): Hold here to heat glow plugs.
5- Start: Spring-loaded to this position (with Pre-Heat engaged) to crank engine; releases back to Run.
 

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   / Regarding "Thermostart" wiring!
  • Thread Starter
#5  
I really appreciate the effort on explaining this but my ignition does not have most of those positions, it's only OFF/Ignition/Start there is no (in between) ignition and start. at this point I will stop the headache and use a four position ignition from a Massey Ferguson because tractor parts stores in my area don't have any parts related to Fords. Sometimes we got to make due with what we have, also on the mean time I will be putting the ignition on the right side how God intended :).
 
   / Regarding "Thermostart" wiring! #6  
Or just add a momentary on push button or toggle switch.
 
   / Regarding "Thermostart" wiring! #7  
I really appreciate the effort on explaining this but my ignition does not have most of those positions, it's only OFF/Ignition/Start there is no (in between) ignition and start. at this point I will stop the headache and use a four position ignition from a Massey Ferguson because tractor parts stores in my area don't have any parts related to Fords. Sometimes we got to make due with what we have, also on the mean time I will be putting the ignition on the right side how God intended :).
Yes, your switch was made for non-thermostart or gas engine models. The replacement will fix that, or as @LouNY said add a momentary pushbutton
 

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