Thanks, will try backing off adjustment first,
Evidently this truck did not come with a lever switch. I have not found any wiring or signs of where one was mounted.
The original wires ran back to a pressure switch, out before the hydrovac.


57 GMC LCF 370
55 John Deere 40-W
59 John Deere 430-W
2000 GMC 4x4
56 John Deere 420-W
Pix on Photobucket