I'm taking some time to remove and clean up the dash area of my D17 IV, and install the tach that Haim at Star Speedometer just rebuilt (beautiful work!).  So I thought I might as well fix up the power director warning light on the dash, which has been broken and not used for the last 40 years or so. 

There is what appears to be a typical (for 1960 anyway) oil pressure switch coming off the base of the hydraulic oil filter.  So far, I haven't found that switch available from the various aftermarket vendors.  I haven't tried Agco, but probably should.  I'm trying to recall, but it sure looks like a plain vanilla oil pressure switch from an old Chevy or Ford.  That won't help me at the modern car parts stores, where they want a part number.  Has anyone replaced this switch (it should be the same for the 170 I would think) with a car oil pressure switch? 

I'm not sure how much good such a warning light is.  If the hydraulic fluid has gotten so low that there is no pressure, I would think there would already be a lot of damage by that time.  I guess it would help in a catastrophic line failure or something, but I would think the operator would be more aware of the gallons of oil spewing out rather than a small idiot light on the dash.  Anyway, I just wanted to fix it just for the heck of it, to pretty up the dash.

The oil pressure light should come on when you turn the ignition to the "on" position, before engaging the starter button.  A good check to see if the wiring/bulb/switch are working, similar to auto's today that usually give you a few seconds of warning lights all on prior to starting the engine. (good check to see if all bulbs working)

The light should go off a few seconds after the engine has started, and you let the foot clutch engage which starts the pump turning, and builds up pressure to the power director/hand clutch.

The light usually comes on when I engage the foot clutch for more than a few seconds, showing oil pressure has gone down in the circuit.  The light goes off once I let the foot clutch out.  

The above applies to my 1963 D17 III Diesel and 1965 D17 IV.  I find the light useful to know there is some pressure working in the circuit.  I check the oil level in the reservoir once in a while, but the light gives easy, quick feedback

Congrats on restoring the Dash area on your D17 IV

The pump noted above in my post is the Power Director Oil Pump, which was common to all D17 models, driven by the transmission gearing/clutch system.

The D17 Series IV has the live Hydraulics Pump located where the old pulley was located on the earlier D17's. That pump turns with the flywheel and provides live pressure to the tractor hydraulics, once the engine is operating

Just wanted to clarify which pump I was referring to in my previous post

Thanks guys for the replies.  I think a (warning) light bulb went off in my head.  Since this light/switch has never been connected or working in the 40+ years we've had this tractor, I just assumed it was a simple idiot light closed by the pressure switch under the hydraulics filter, and that it only came on if one totally ran out of hydraulic fluid.  Am I wrong, and does this switch indicate loss of pressure to the Power Director, rather than the general hydraulics?  Does it indicate a clogging filter, with less flow? 

What the heck is this light supposed to indicate? I'm just curious.

Doc,

Thanks so much.  It makes more sense now.  I still don't quite understand why pushing the foot clutch in would make the light go on, since the hydraulic pump is live to the engine? 

There are two separate pumps here in this discussion...........

The first is the Power Director Oil Lube Pump which moves lube oil thru the filter and into the Power Director/Hand Clutch.  The pressure switch and dash light are part of this system.  The Pump is driven by the foot clutch/transmission system, hence when you push the foot clutch down the pumps stops, and eventually the light comes on.  This pump is located within/attached to the tractor torque tube.  All D17 tractors were fitted with this pump. 

You are absolutely correct ...........the light indicates a loss of pressure to the Power Director / Hand Clutch (not a good situation)

The second pump in this discussion is part of the Hydraulic Lift System for the tractor-  lift arms and remote ram connections at the rear of the tractor.  This pump is located on the right hand side of the tractor, where the old pulley was connected to the Series !, II, III tractors. Only D17 Series IV Tractors were supplied with this pump