Coolant temp gauge: reality check pls

[Steve in VA]

Got mini home and temp gauge reads 0 all the time. Its a single wire to the sender. I 'assume' that power goes to the gauge, out to the sender, and then to ground. As temp changes, resistance changes and gauge reading follows.
W/ ignition on I have no voltage at the sender. All fuses check as good.
The manuals I have are limited on this. The sender was removed for recent head/valve work. The single wire runs a fee inches then into a common loom to the console. That looks intact. I really hate the idea of tearing into the console to access the gauge so im looking for options.
TIA
Oh, and everything else works.

 

[RJKeith]

Is it a single wire or a thermocouple?

 

[Steve in VA]

Is it a single wire or a thermocouple?

Seems a single wire to the sender. My VOM died so I have to make do w/ a test light.
So here's another piece. I just unlanded the wire from the sender and w/ ign on the test light shows voltage. When I reland it to the sender it shows nothing. I stressed the wire unloaded and the light never wavered. I'm inclined to dead sender.

 

[Brown David]

Seems a single wire to the sender. My VOM died so I have to make do w/ a test light.
So here's another piece. I just unlanded the wire from the sender and w/ ign on the test light shows voltage. When I reland it to the sender it shows nothing. I stressed the wire unloaded and the light never wavered. I'm inclined to dead sender.

Don't know what you're working on so this might not apply to newer computer controlled stuff.


I think if you ground that wire, with the ign. on, the gauge should go full scale. If it does, the sender is the problem.

 

[Dingo3]

Also, check if they used teflon tape or too much sealant when reinstalled. This will interfere with the sender’s contact to the engine/ground.

 

[Steve in VA]

Don't know what you're working on so this might not apply to newer computer controlled stuff.


I think if you ground that wire, with the ign. on, the gauge should go full scale. If it does, the sender is the problem.

I tried that first with no luck so moved on. Worth a follow up though.

 

[BarnyardEngineering]

If you're just poking the sender's terminal with the test light you're not going to get anything from your test light. The resistance is too high.

Grounding the wire from the gauge should cause the gauge to peg. Since it doesn't that means bad gauge.

 

[Steve in VA]

Got mini home and temp gauge reads 0 all the time. Its a single wire to the sender. I 'assume' that power goes to the gauge, out to the sender, and then to ground. As temp changes, resistance changes and gauge reading follows.
W/ ignition on I have no voltage at the sender. All fuses check as good.
The manuals I have are limited on this. The sender was removed for recent head/valve work. The single wire runs a fee inches then into a common loom to the console. That looks intact. I really hate the idea of tearing into the console to access the gauge so im looking for options.
TIA
Oh, and everything else works.

Did I mention that I'm an idiot? Should have. While running all the checks and focused on a temp gauge pegged 0, I failed to see the oil pressure light going off and on. Yup, wrong sender. Of course I can't locate the correct sender anywhere but its dark in the engine bay and getting hot so time to sit down and reflect on how I can better my situation.
More to follow.

 

[Dingo3]

Did I mention that I'm an idiot? Should have. While running all the checks and focused on a temp gauge pegged 0, I failed to see the oil pressure light going off and on. Yup, wrong sender. Of course I can't locate the correct sender anywhere but its dark in the engine bay and getting hot so time to sit down and reflect on how I can better my situation.
More to follow.

What make, engine and year?

 

[Steve in VA]

What make, engine and year?

CAT 3003 engine year [?].
Everything says its screwed into the thermostat housing but nothing i can see or feel. No wire visible either. Looking like a drive to CAT dealer tuesday.

 

[Jim.ME]

Check in the head, behind the thermostat housing.

 

[Dingo3]

CAT 3003 engine year [?].
Everything says its screwed into the thermostat housing but nothing i can see or feel. No wire visible either. Looking like a drive to CAT dealer tuesday.View attachment 154409View attachment 154410

I could not find a decent photo of location but I did read where it could be in the head.
I did’nt see your post when replying @Jim.ME

 

[Steve in VA]

Check in the head, behind the thermostat housing.

View attachment 154411

Great lead. I'll get in the shop and remove the hood do i can see there. Msy need to pull some air cleaner bits too. I can't see down in there now but felt around and felt nothing. Hood off and inspection mirror will help.

Thanks much.

 

[Steve in VA]

Got mini home and temp gauge reads 0 all the time. Its a single wire to the sender. I 'assume' that power goes to the gauge, out to the sender, and then to ground. As temp changes, resistance changes and gauge reading follows.
W/ ignition on I have no voltage at the sender. All fuses check as good.
The manuals I have are limited on this. The sender was removed for recent head/valve work. The single wire runs a fee inches then into a common loom to the console. That looks intact. I really hate the idea of tearing into the console to access the gauge so im looking for options.
TIA
Oh, and everything else works.

Youse guys are Rockstars. Jim.ME had a pic. I had to remove the hood and part of the air cleaner but it was exactly there. I still never saw it so operated by braille. After I located the sender I could feel around until I stumbled across a loose wire. Got immediate meter deflection and ran up to indicated operating temp.

I can't thank you guys enough. In the bond of old machines that can be cantankerous, thanks!!!

 

[Texasmark]

On the subject of thermostats, I bought a CIH 395 a couple of years ago. Changing the thermostat, sending unit and dash was part of the initial to do list. Interesting observation. I flushed the cooling system and refilled with 50-50 distilled water and diesel rated anti-freeze.

If the tractor has been sitting for awhile, in operating the first time, the needle goes into the red about mid way and stays there, but a non contact infrared thermometer (have 2 for comparisons) aimed at several points says the temp is where it needs to be. If I use the tractor again, within a short time span, the needle settles where it is supposed to be. My first thought was that the thermostat was sticking until I measured the actual temps. Just a peculiarity that I can now forget about about.