I "instrumented" the solenoid valve and valve going to the transaxle clutch. I put a "T" in the outlet of the valve and a VOM meter reading volts on the input to the solenoid coil. I routed a hose with a gauge and leads with a VOM up to the grip handles at the front of the interior of the cab and mounted them both with wire ties. The thought was to monitor both the next time the owner wanted to use the 4wd. We started the tractor and engaged the 4wd button. Pressure went to a little over 200 PSI (should be 225 PSI-275 PSI as I recall and coil voltage went to 11.7x volts. (an earlier test showed the 4wd switch was dropping 0.3 volts. Coil is 14 ohms warm.)
After about 30 seconds of the above operation the pressure dropped to zero and the voltage at the coil went completely nuts, all over the map.
Long story short after much head scratching and studying the schematic, I hooked a jumper lead from the ground side of the coil to the battery negative (tractor ground) post. The problem went completely away. I then pulled back the dash panel about 4", there is some creative wiring in there. So, the next step is to take the tractor down a few days and completely remove the dash and go through the wiring and grounds. By he way, fuse wiring does not match the schematic. Again, this may be due to some creative wiring I observed behind the dash.
Sorry about the length.
Paul
After about 30 seconds of the above operation the pressure dropped to zero and the voltage at the coil went completely nuts, all over the map.
Long story short after much head scratching and studying the schematic, I hooked a jumper lead from the ground side of the coil to the battery negative (tractor ground) post. The problem went completely away. I then pulled back the dash panel about 4", there is some creative wiring in there. So, the next step is to take the tractor down a few days and completely remove the dash and go through the wiring and grounds. By he way, fuse wiring does not match the schematic. Again, this may be due to some creative wiring I observed behind the dash.
Sorry about the length.
Paul
