Ford 6640 PTO Short

[Robert Mader]

Check the blue "safety" relay in the fuse/relay cabinet on the right of the dash before you get into rear end. We were having the same problem with our 6640 and bypassed the safety relay. It works fine now. The safety relay senses alt power to keep power going to the pto solenoid so if the tractor stalls or is shut off with pto on you have to cycle the switch to get pto to work again when it is restarted. The relay must of shorted internally on ours causing the fuses to keep blowing. What you must remember is with this relay bypassed the pto will remain engaged if you stall or shut off the tractor and then restart it.

Hi , I have a 96 / 6640 and have the same problem , mine won't blow the fuse , but will run for two hours , or 5 min. no rhyme nor reason . I can restart the " new " switch I replaced and may shut right down or may run for hours ... Can the Safety switch be replaced ? and do your think this s the same problem where the fuse does not blow ??

 

[Robert Mader]

Hi did you get yours to work this way and if so does it go right back to the pto switch ?? any help would be great ... No one in my part of Canada seems to know anything about these tractors .. Thank you

 

[Jackfr]

Hi

Once we removed and bypassed Safety relay (in the pictures above)in our 1992 6640 the pto works fine turning on and off with the pto switch now. I think all the relay is for is so the pto won't restart if you shut off the tractor without shutting off the pto switch and then restart the tractor. We put the fuse inline to further protect the circuit, but be aware the pto will turn on when you restart the tractor if you leave the pto switch in the on position. We also had intermittent pto before removing and bypassing the relay. This intermittent problem could have been caused by a failing safety relay or as one person informed me possibly a bad or failing alternator as he said the relay senses if the engine is running by a sensing wire from the alternator. Our alternator totally failed and we replaced it a few months after doing the bypass but we left the bypass in place.

 

[Kent woods]

Looking for some advice on my Ford 6640. Everytime I engage the PTO switch, it works for a second and the blows the fuse. We tried replacing the switch and this did not work. We have check most of the wiring pretty good but cannot find a the short. Any suggestions on any other areas that we should be checking for this problem?