I have a John Deere F510 riding mower that keeps blowing the PTO fuse.
The strange thing is that it does not blow it right away, and it
doesn't always blow it. Here are the sysmptoms:

1. I put a fresh 15 amp fuse in the PTO.
2. Start up the mower, it runs fine.
3. Engage PTO, it works fine.
4. Mow the yard for at least 10 minutes, it works fine until the first
time I disengage the PTO.
5. Once Disengaged, the PTO will not work again.
6. Wait until the next day and start over at #2.
7. This cycle repeats a few more times and then, while mowing, the
engine cuts off. Upon inspection, the 15 amp fuse to the PTO has been
blown.

Now, some background. I have discovered that when the key is on but
the engine is not running, I can engage the PTO (with a fresh fuse)
and I can hear the PTO clutch engage. No problem here, however, if I
leave the clutch engaged for about 1-2 minutes, I can feel practically
all the wiring becomming hot. Everthing from the Ignition switch
(key) to the wires coming off of the PTO clutch (these are VERY hot).
I thought heat was involved when I noticed that each of the blown
fuses would have the blue plactic melted on the left side if the fuse.

I have a "Technical Manual" for this mower (Thanks E-bay!) but
apparently I need to know more about electrical ciruits to figure this
one out. I have found in the manual were it gives "PTO Circuit test
points". It shows were to place a volt meter and the "normal"
results. I have tested eveything it lists except for one test that I
don't know how to perform. More on that later.

There is only one test that doesn't give me the "normal" results. It
says that if I test the following I should get the battery voltage (my
meter shows 12.4 between the battery's negative and positive
terminals). I don't quite, in this test my meter shows 11.6 (about
10 other tests do show the battery voltage of 12.4). Here are the
conditions: Trans. in neutral, parking break engaged, PTO disengaged,
ignition switch in RUN position, Meter - on negative battery terminal,
meter + on PTO relay terminal 85. The manual shows "if not normal"
check pur/wht wire and diode. I checked the wire itself and cannot
find anything visually wrong. My big question is what is the "diode"?
Could it be causing my problem? Can a new "diode" fix my problem?

The test that I do not know how to do is one in which the manual says
to test the clutch itself. It says that the normal is "minimun PTO
clutch current draw - 4 amps". I don't know how to measure the
"minimum current draw." It says that if this is over 4 amps to
replace the clutch.

So, my questions are, is my problem the diode in the PTO relay
terminal. or the fact that I can't measure the amperage draw on the
clutch and my clutch is really bad. I have attempted to adjust the
air gap on the clutch, and I think I have it set at the .020 inch gap
as recommended.


I appreciate any help you can offer.

Thanks.
CRR
Little Rock, AR

A diode is a electrical one way valve so to speak, it will allow current to
travel in one direction only. use a ohm meter to test you should get a
reading measurable resistance in one direction and infinite when you reverse
the test leads.

the low voltage reading could be cause from a poor connection, loose
connection (loose connections will also cause amp to go up and heat to be
generated) ect.

the test for amp draw you want to place a amp meter in line in other words
disconnect the one line to the PTO clutch and wire the amp meter so the
current will go through the meter start up engage the PTO and see readings.

make sure you don't have part of the meter, your fingers or wires in the
way of the PTO where it may get caught in.

If the PTO is disconnected at the PTO will it still blow fuses when you
engage the switch? do the wires get hot? If so you may just have a power
wire that is partially grounded creating the high amp draw and causing heat
and blown fuses.
hope that helps

"Dr. Doctor" wrote in message t...
A diode is a electrical one way valve so to speak, it will allow current to
travel in one direction only. use a ohm meter to test you should get a
reading measurable resistance in one direction and infinite when you reverse
the test leads.


it 's a bad field winding in the PTO clutch. Not uncommon. replace the clutch.
Chip