PTO Slips on Ford 6640 SLE

Astralo

Member
Livestock Farmer
Hello, I have a 6640 SLE with a PTO problem. The PTO works correctly but it slips, it has no power. We disassembled the rear lift cover twice. The first time we found that the oil supply hose was loosely connected to the PTO valve, and the solenoid supply wires were bare. We repaired and we took the opportunity to change the clutch plates. Once reassembled, the PTO still slipped. So we disassembled again, and we changed the complete clutch housing, as well as the housing mounting bracket. The PTO still does not work, it continues to slip. So we're thinking of changing the PTO valve, since that's the only thing we haven't changed yet.

Do you have any other Ideas?
 

agrimax

Member
Location
Co Down
The control valve may not be engaging fully due to a weak solenoid or not enough volts reaching it. Have you checked the alternator output is around 14.4v as it sends a signal to the pto control module in the fuse box when the pto knob is turned on?
 

Astralo

Member
Livestock Farmer
We checked the voltage directly on the connection lug of the solenoid on the left rear of the tractor, and we get about 14 volts when the PTO is engaged. We also tested the solenoid outside of the tractor using a battery, and it seems to work well; you can hear it open and close.
 

Mur Huwcun

Member
Livestock Farmer
Location
North West Wales
We checked the voltage directly on the connection lug of the solenoid on the left rear of the tractor, and we get about 14 volts when the PTO is engaged. We also tested the solenoid outside of the tractor using a battery, and it seems to work well; you can hear it open and close.
Did you test with just a multimeter or with a load on? Rig a h3 halogen bulb type up and see how bright it is, that will load the circuit up
 

Astralo

Member
Livestock Farmer
We tested with a light bulb. PTO won't engage when the bulb is plugged in. It's like the bulb is drawing too much power and it's preventing the PTO from engaging. Maybe the light bulb is causing the voltage to drop below 14V, and this is preventing the PTO module from engaging? When the solenoid is reconnected, the PTO engages normally.
 

Mur Huwcun

Member
Livestock Farmer
Location
North West Wales
We tested with a light bulb. PTO won't engage when the bulb is plugged in. It's like the bulb is drawing too much power and it's preventing the PTO from engaging. Maybe the light bulb is causing the voltage to drop below 14V, and this is preventing the PTO module from engaging? When the solenoid is reconnected, the PTO engages normally.
Does the bulb light up bright and stay bright? is it a 55w minimum bulb as it needs to load up the circuit to stress any weak, dirty or loose connections. If it does then it’s a fairly clear indication that your electrical side is as it should be.
 

Astralo

Member
Livestock Farmer
No, the bulb stays off, it's like the PTO module refuses to engage when the bulb is plugged in, so it's not sending power. It is a 55w bulb, but it does not light up at all, although it works when I plug it into the battery. So there is an electrical problem, but I don't know where to look for it, maybe it's the alternator or the PTO module?
 

Astralo

Member
Livestock Farmer
I'm not sure there's a PTO speed sensor on this tractor, since even when the PTO slips, it won't stop. I tried to search if there was a PTO speed sensor on this tractor, but I couldn't find the information.

I think we'll try running 12V Directly to the solenoid, to see if the PTO is working properly, and we'll try to find out what the electrical problem is.
 

Mur Huwcun

Member
Livestock Farmer
Location
North West Wales
I'm not sure there's a PTO speed sensor on this tractor, since even when the PTO slips, it won't stop. I tried to search if there was a PTO speed sensor on this tractor, but I couldn't find the information.

I think we'll try running 12V Directly to the solenoid, to see if the PTO is working properly, and we'll try to find out what the electrical problem is.
That would be first step, see if the actual mechanical side of things are ok
 

Astralo

Member
Livestock Farmer
We tested the PTO by running electricity directly to the solenoid. We tried an agricultural mulcher to test. The PTO spins, but as soon as the mulcher takes too much power, it still slips. So there is definitely a mechanical problem. However, the only parts that have not been changed in the PTO clutch are the valve and the solenoid.
 

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