Ford 7740sle

[Nick T K]

Ford 7740 pto problem
It has had a new alternator
New battery
New switch
New switch bulb
We checked as much wiring as we think is related when you disconnect plug near solenoid the pto light comes on when you reconnect it goes off.
When put a direct fused feed from battery to the plug everything works perfectly
Any one come across this before any help gratefully received

 

[Bern]

Based on your description, the circuit is functioning as intended because the indicator light comes on when you turn the switch on. If the signal from the alternator was faulty or missing, not even the light would come on.

Because the light only comes on when you disconnect the PTO solenoid, that tells me that the PTO module does not have enough power available to supply current to both the light and the solenoid at the same time. This leads me to believe that you have excessive voltage drop (a.k.a. resistance) somewhere in the circuit that sends power to the PTO module (see red trace in diagram below). Probably the quickest and easiest test to check for power would be to connect a 5-amp load, such as a typical incandescent headlight, to the socket at pin 7 of the PTO module. The light should be nice and bright.

If it's dim or doesn't come on at all with the key switch on, you have problems somewhere in the circuit traced in red, or even upstream from fuse #21. I would be particularly suspect of connector #4. Even if you don't have the shiftable 540/1000 switch, there should be a bypass connector plug in its place that could be corroded.

If all else fails, it wouldn't take much to do a little re-wiring to make the switch control the PTO solenoid directly, instead of having to go through the PTO module. Be advised however that you'd be defeating the purpose of the module, which is for safety only. It prevents the PTO from coming on should the engine stall and be restarted.

 

[showcrop]

Does it have a cab? My 8240SLE would do that when I was having problems with the AC.

 

[Nick T K]

Thankyou and much appreciated the information you so kindly gave to me I printed it off so have for future reference I have checked all wiring and pto goes sometime other times not I have got 13volts at + on the switch 13v on c on switch and 0.9 volts on T on the switch is this correct and if I put my tester on the bulb there is 13v there it is becoming a real headache now thankyou for your time and effort

 

[Bern]

Check for power at pin 7 of the PTO module socket (not the module itself) as I described in my last post and report back. Use a 5-amp load, NOT a meter!

 

[Nick T K]

Thankyou for all your help I think I have found the problem the wires are touching /shorting where it goes through the grommet to solenoid so wheel and tank have to come off to get to the plate so hopefully it will solve it thankyou once again