Just noticed the temp gage on my 1920 isn't reading. I figured when the key is turned it should peg out to show it works but it isn't. When the tractor is warm the gage still won't move. I figured maybe a stuck open thermostat but that should have nothing to do with the gage not moving at all. Do you think it is Sending unit or gage?
- Thread starter JohnAR
- Start date
Tom in TN
Well-known Member
- Location
- Southern Middle Tennessee
John,
Is there any chance at all that your coolant level is so low the temperature sending unit isn't getting covered by coolant?
Tom in TN
Is there any chance at all that your coolant level is so low the temperature sending unit isn't getting covered by coolant?
Tom in TN
tractorguy2
Well-known Member
I would think if you grounded the wire on the sending unit the gauge would peg.
Thanks I am not that electrical so I didn't think of grounding it. I did that and the gage works. I went ahead and ordered a sending unit. I thought while I was at it I would get a thermostat just to have on hand but it was $39. I figured it would be a cheap run of the mill item but I was wrong.
The radiator level is full.
The radiator level is full.
Texasmark1
Well-known Member
My '65 3000 has an electric instrument panel. The fuel and temp are wire wound resistors and are in series with the sending unit across 12v and ground. I have seen both and the wire seems to be about the same size.
On fuel gauges there is a minimum resistance of about 35 ohms, when the gauge is at limit, in the sending unit. On the other end the resistance is about 235 ohms as I recall. Would expect the temp to be similar. Shorting around that could slam the meter to the peg and bend the needle or worse burn out the gauge wiring.
I would use an ohm meter to check continuity and then a voltmeter to ensure supply and ground at the extremities. A bad ground at the sensor end could be your problem which is probably the case of the sending unit as there is usually only one electrical terminal on a sending unit.
HTH,
Mark
On fuel gauges there is a minimum resistance of about 35 ohms, when the gauge is at limit, in the sending unit. On the other end the resistance is about 235 ohms as I recall. Would expect the temp to be similar. Shorting around that could slam the meter to the peg and bend the needle or worse burn out the gauge wiring.
I would use an ohm meter to check continuity and then a voltmeter to ensure supply and ground at the extremities. A bad ground at the sensor end could be your problem which is probably the case of the sending unit as there is usually only one electrical terminal on a sending unit.
HTH,
Mark
No the coolant level is full. I put a new sending unit on and it made no difference. Having recently purchased this tractor I thought I would replace the thermostat just to make sure the previous owner wasn't running it without one. The old thermostat tested fine in hot water but I put the new one in. what is weird it that I ran the tractor for about an hour and I swear the thermostat never opened because the level never went down and I couldn't feel any coolant in the upper hose. The level should have gone down as it circulated to refill what was lost from the block when I removed the thermostat. However if that was the case you would have figured it would have overheated. It never did and you could hold your hand on the engine block and I wasn't hot. I never owned a diesel is there something about them that I don't know? I put the thermostat in correctly. There may not be a problem but I would feel better if the gage worked to confirm that it is operating at the proper temperature.
Sean in PA
Well-known Member
You do have to work a diesel pretty hard to get it to really warm up. If you were just driving around with the rpm's fairly low then it might not have heated up enough to open the thermostat, espcially as cold as it's been in some parts of the country lately.
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