1566 Air Pressure Guage

I'm almost finished getting the tractors factory electrical system restored on my 1566 - doing all used parts - everything works good now except my air filter gauge.

I've put on a new sending unit and replaced both the inner and outter filters and replaced the air sensor sending unit.

I had to guess about the gauge connections however cause the original had been removed by the former owner and he installed an aftermarket water sensor there - which I've removed.

But, I've only started the tractor briefly- mostly cause its cold and also because most of the sheet metals still from the clutch replacement but when I've started it - it stays on red.

Any ideas on that? Does it need to be running to be on green?

Hello Tom Barto,

Only gauge I know used on an air cleaner is a
air restriction gauge. Sometimes called filter minder. Some of them have a button that will reset the gauge if the filter was clogged and went red.
That gauge is graduated in inches of water column, and will register 5" to 10" normally
When it reads 15" to 18" it is still a usable filter. 20" to 25" time for a new one.
Guido.

Hello Tom.

I put a complete new wiring harness on an 856 I restored a year ago, and remember the air restriction indicator wiring well. Assuming an 856 and 1566 use the same system, this is how the 856 system works.
The green / red gauge defaults to the red zone when no power flows through the gauge.
The restriction gauge takes power from the ignition switch to one gauge terminal and grounds the other gauge terminal through the sender at the air cleaner. The sender at the air cleaner has two terminals, one is connected to ground near the sender and the other terminal connects to the gauge terminal.
The sending uniot at the air cleaner is just an on / off vacuum switch so normally it grounds the gauge which puts the needle in the green zone. When restriction vacuum gets high enough, it opens the sender switch, which opens the gauge circuit to ground and allows the needle to swing to the red zone.

If yours remains in the red zone, look for no power to the gauge, or an open circuit in the ground circuit, through the sender switch to ground on the engine.
If the gauge is known to be good, your problem has to be in the 12V supply circuit to the gauge, or in the ground circuit that goes through the sender switch to ground on the engine.

Jon - yours sound like exactly what I have...I know I have ignition power to the gauge which comes in on the right side of the gauge sitting in the tractor...Assuming I recall properly - it goes hot when the key is turned for start.

The other side of the gauge, If I recall, I've read both ground and 12V.

I'll have to play around with it..

I'll guess it doesn't want to read 12...maybe probably, I'm guessing based on your description, its wants to be some delta V < 12V???

I'll play with it...thanks...

I believe the sender is just a normally closed pressure switch that when their is enough restriction, the switch opens and lets the gauge default to the red zone.
I don't believe the gauge will read anything in between red and green, just red when the vacuum switch opens, green when it is closed, so the gauge will read green until their is enough restriction vacuum to open the switch, then go full green to full red.

Guido:

You're referring to a MECHANICAL guage with a MANUAL reset. Tom is referring to an ELECTRICAL system that senses the increased vacuum that is created when the filter plugs up. I have worked on similar types on mining machinery.

Hello,

Now i know about the sensor he was talking about. On raod systems is what i have seen so that si a different animal.
Hard to tell the palyers with out a score card.
Thanks for the info, new one on me!
Guido.

Well...still no go....

I've verified continuity between the LHS terminal and the plug to the new filter sensor...

The two nodes on the filter sensor also have continuity and are ground when I hook one of them to ground.

That takes me to ground all the way up to the filter sensor gauge...

So, I have the gauge all the time on red - ignition on 12V on one terminal and ground on the next....

All new inner and outter filters and a new filter sensor...

The gauge is used...

How often do they go bad?