Engine pre heat not working 7495

[J50WAT]

Looking for some advice if possible!
The thermostart on my MF 7495 teir II isn't working. I can get it to come on by putting a direct feed to the relay, but the ECU won't activate it and it won't come on with holding the ignition key inbetween ignition position 2 and start.

After the engine is running, the engine pre heat light comes on for the post start up phase of the grid heater, but it won't come on before the engine is running. Making it hard to start on a cold morning.
Anyone else had a similar issue with the Sisu engines?

Thanks

 

[Mur Huwcun]

No idea on a Sisu but it sounds like you have a wiring issue or most probably a temp sensor issue. Usually the ECU will only let you pre heat if the coolant is cold enough. How many sensors does it have? Is there a sensor with twin wires?

 

[J50WAT]

According to the workshop manual, the Grid Heater has a pre heat phase before starting, and a post heat phase once the tractor is running. The ECU controls when the pre and post heater is activated, but the Massey workshop manual and the Sisu diesel engine workshop manual doesn't actually say what drives the ECU to activate the grid heater (I.e the inlet manifold temp, outside air temp, coolant temp, etc).

See the screen shots below of the manuals.

 

[norse]

According to the workshop manual, the Grid Heater has a pre heat phase before starting, and a post heat phase once the tractor is running. The ECU controls when the pre and post heater is activated, but the Massey workshop manual and the Sisu diesel engine workshop manual doesn't actually say what drives the ECU to activate the grid heater (I.e the inlet manifold temp, outside air temp, coolant temp, etc).

See the screen shots below of the manuals.

I had a problem with the grid heater on my t3 7495 ,it displayed error 9171 and made the dash warning lights flash ,I fitted another heater control relay located on the manifold ,this cured it for a couple of days then it returned so I set about following the wires back into the loom and found one of them rubbed through with the corrugations of the conduit,I cut this out and spliced some more wire in to sort it,I know this isn't the problem that the op is having but my tractor didn't have a problem starting

 

[norse]

I had a problem with the grid heater on my t3 7495 ,it displayed error 9171 and made the dash warning lights flash ,I fitted another heater control relay located on the manifold ,this cured it for a couple of days then it returned so I set about following the wires back into the loom and found one of them rubbed through with the corrugations of the conduit,I cut this out and spliced some more wire in to sort it,I know this isn't the problem that the op is having but my tractor didn't have a problem starting

As can be seen it had cut through the wire

 

[Timbo]

According to the workshop manual, the Grid Heater has a pre heat phase before starting, and a post heat phase once the tractor is running. The ECU controls when the pre and post heater is activated, but the Massey workshop manual and the Sisu diesel engine workshop manual doesn't actually say what drives the ECU to activate the grid heater (I.e the inlet manifold temp, outside air temp, coolant temp, etc).

See the screen shots below of the manuals.

Got to be ambient or inlet air temp the former I suspect. Can the OP check the resistance of his sensors to see if any are wildly out ?