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.

 

[dickfoster]

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.

Well most dealers can kiss where I can't. This is a brand new tractor under warranty. It is supposed to work and believe me, it will.

 

[Chuckk]

Does your tractor have the small hose coming from the top of the radiator to exhaust cooling system
its about the size of a fuel line. If it does have that hose that will be your problem it is allowing to much of the coolant to by pass the thermostat Mahindra is aware of the problem and has a mod for it I had the same issue on my new 4550 until the Dealer did the mod they install a restricter in the hose If you have that hose you can verify The problem squeeze off that hose with a pair of vice grips and run the tractor for 15 or 20 mins and your gauge should start going up. Does not hurt any thing that hose is only to keep air from being trapped put is allowing way to much coolant flow.

 

[jb1390]

Does your tractor have the small hose coming from the top of the radiator to exhaust cooling system
its about the size of a fuel line. If it does have that hose that will be your problem it is allowing to much of the coolant to by pass the thermostat Mahindra is aware of the problem and has a mod for it I had the same issue on my new 4550 until the Dealer did the mod they install a restricter in the hose If you have that hose you can verify The problem squeeze off that hose with a pair of vice grips and run the tractor for 15 or 20 mins and your gauge should start going up. Does not hurt any thing that hose is only to keep air from being trapped put is allowing way to much coolant flow.

x2

I have another thread that details this problem with my 3550.

 

[carmedic310]

oops didnt realize this was a new tractor

 

[cornfedhogeditor]

FYI the obdII is hidden in the engine compartment on the left hand side by the main fuel filter. It was zip tied to the harness between the wire harness. I'll put a pic up of the location next time I am at the tractor.

 

[dickfoster]

Does your tractor have the small hose coming from the top of the radiator to exhaust cooling system
its about the size of a fuel line. If it does have that hose that will be your problem it is allowing to much of the coolant to by pass the thermostat Mahindra is aware of the problem and has a mod for it I had the same issue on my new 4550 until the Dealer did the mod they install a restricter in the hose If you have that hose you can verify The problem squeeze off that hose with a pair of vice grips and run the tractor for 15 or 20 mins and your gauge should start going up. Does not hurt any thing that hose is only to keep air from being trapped put is allowing way to much coolant flow.

Thanks, I'll lift the hood and give that a look see.

If it's causing engine temp to be misread by the ECU also, that could be a real problem and not just a simple gauge issue.

 

[dickfoster]

FYI the obdII is hidden in the engine compartment on the left hand side by the main fuel filter. It was zip tied to the harness between the wire harness. I'll put a pic up of the location next time I am at the tractor.

Thanks, I'll look for it in there. Maybe I didn't poke around hard enough and I wasn't looking for something just flopping around loose. I'm sure it's the same for 33s and 38s because they have the same engine. At least when I find it, I can plug my scanner in and see if the ECU is seeing the right engine temp.

 

[dickfoster]

Thanks again, I found it. It was just flopping around in there loose. Now I can plug in my scan tool and see if there is actual engine temperature. I might find a way to mount the OBDII connector too, it looks shadetree they way they have it.

 

[Chuckk]

If you have that hose your temps will be very low because much of the coolant is by passing the thermostat .
There is another thread all about this I had tested the sensor and gauge including all wiring before finding out the real problem.

 

[dickfoster]

If you have that hose your temps will be very low because much of the coolant is by passing the thermostat .
There is another thread all about this I had tested the sensor and gauge including all wiring before finding out the real problem.

I looked around the top of the radiator and found no small hose but I'll look harder when I can get it out into some daylight.

The only odd thing I have found is a steel whatamacallit in line with the lower radiator hose. There are two metal plugs in it but I haven't determined what function it has if any. Just a big hose in and a big hose out. I'm sure they didn't pay for something to do nothing that has no function. Maybe a good place to tap in a cab heater return line or somesuch. I'm also very new to this oil burner stuff so still have much to learn. Although when they say compact tractor they really mean it. I thought it was tight under the hood of my truck but this looks tighter.