Temp gauge question.

[dickfoster]

I recently got a 1538, it's my first tractor. I spent a few hours on it today running mostly around 1500 RPM with the backhoe, yet to date I've never seen the temperature gauge register anything but stone cold. Is this normal or is the gauge busted on this brand new machine? The temperature out today was mild, in the high 60s and low 70s so I expected after a couple of hours of run time to see at least some reading on the gauge.

 

[Alien]

It should register quite quickly. Problem could be a faulty guage, loose wiring connection, or stuck (open) thermostat. I would check the thermostat first. Talk to the dealer. It can do serious harm over time running a motor cold.
Hopefully nobody has removed the thermostat due to a motor heating problem.
IF, this was the case the radiator could be partially blocked.

 

[crankshaft21]

First check your temp guage. Then check the temp sending unit. If both are working, check wiring from sending unit to the temp guage.

 

[dickfoster]

First check your temp guage. Then check the temp sending unit. If both are working, check wiring from sending unit to the temp guage.

I guess I'll call the dealer. As I said this is a brand new tractor and is under full warranty and it's been this way since day one. I didn't want to get too worried about it until I got some hours on it and the weather warmed up a bit. The reason I asked was because this could be completely normal for a new Mahindra with tier 4. I'm a tractor newbie so didn't want to go off half cocked with a hair trigger. I was hoping Dave would chime in too.

 

[dickfoster]

I unplugged the temp sensor yesterday and read it with an ohm meter cold and hot. It's changing resistance, about 1.5K cold and about 500 ohms at operating temp, so I suspect the sensor is good. I also read about 3.5K on the sensor leads so it's connected to something, its definitely not an open lead.
I suspect the temp sensor is connected to the ECU but as the so called service manual doesn't have a schematic for the engine harness so I don't really know for sure. Most engine management schemes have to know operating temp to function properly so I imagine this one does too. When I turn the key on the temp gauge scans up to full then back to zero so I suspect the gauge and the little microcontroller that runs it are good to go since the tach and other readings are good.
I suspect the gauge CPU is driven by the ECU but without a proper wiring diagram I don't know for sure. Does anyone here have an engine harness diagram for a 1533 or 1538? My guess is that they are the same. The only wiring info in the service manual I have are the chassis wiring harnesses.
Mahindra's documentation sucks big time.

 

[cornfedhogeditor]

I have the 1533 and mine reads cold or 1 bar max when it is over 75degF. I also have a check engine light of P1801.

 

[dickfoster]

I have the 1533 and mine reads cold or 1 bar max when it is over 75degF. I also have a check engine light of P1801.

Don't know if it's relevant but OBDII P1801 = Transmission Clutch Interlock Safety Switch Open Circuit

I saw a reference to OBDII in the service documentation somewhere but don't see an OBDII diagnostic plug anywhere yet. If there is one, maybe it's buried behind the instrument cowling.

Max temp at only 75DegF doesn't sound quite right either.

 

[carmedic310]

Usually the temp sending unit for the gauge is not the same coolant temp sensor for the ecm Most have 2 different sensors not sure on your model

 

[dickfoster]

Yeah it's that way on my truck. I've looked around the engine and only see the one temp sensor just below what looks like the thermostat housing. I don't have an engine harness diagram but wish I did. You'd think it would be in the service manual but it isn't. Mahindra seems to pretty much suck for anything relating to paper or software.

 

[carmedic310]

Most dealers will not answer any questions they will just tell you to bring it in.Your other option is to find a place to put a new gauge in with a mechanical type sending unit instead of electric.Cheap money at the part stores.