PTO Contactor Problem

PTO Contactor Problem

Postby jtcweb » Tue Jul 08, 2014 12:35 am

OK I'm getting closer to success. However when I run the mower something bad happens after mowing for just a couple of minutes. The PTO cuts our and it tripped the breaker as well. Then when I try to engage the PTO circuit (even with nothing attached) the PTO contactor goes back and forth between energized and non-energized. So something is still not right and I suspect it is still pulling too much current. Can anyone help me?
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Re: PTO Contactor Problem

Postby Jeff Antonucci » Tue Jul 08, 2014 12:57 am

What is your pack voltage when this happens? Also check your relays. A weak relay connection could do this.
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Re: PTO Contactor Problem

Postby jtcweb » Tue Jul 08, 2014 1:00 am

Which Relay should I check?
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Re: PTO Contactor Problem

Postby Jeff Antonucci » Tue Jul 08, 2014 1:06 am

What model tractor?
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Re: PTO Contactor Problem

Postby jtcweb » Tue Jul 08, 2014 2:15 am

It is an E20.

I tried it again and when in a lower gear and was able to mow for about an hour (it got too dark to see even with the lights). The battery pack was down to 34.75V. Still every time I tried to engage the PTO the contactor chattered a few times before it held.
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Re: PTO Contactor Problem

Postby FarmallMan » Tue Jul 08, 2014 1:24 pm

Possible items to cause PTO chatter are: faulty PTO switch, faulty 1RTN relay, faulty PTO contractor coil, or a good sized short circuit path drawing down the circuit voltage.

Which circuit breaker opened? The PTO should be able to supply a very large amount of power without tripping any breakers. The mower shouldn't trip any breakers on the tractor, however the breakers mounted to the motors commonly trip for a variety of reasons. Have you assessed the condition of the mower motors yet. Unless they've been rebuilt lately, I'm betting they need at least new bearings.

Nick 8-)
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Re: PTO Contactor Problem

Postby jtcweb » Tue Jul 08, 2014 1:48 pm

The PTO contactor has just been replaced. The old one had one leg of the metal plate the moves melted off, but also would chatter sometimes. This machine has sat for 30 years in a barn so I'm wondering if some of the relay contacts are corroded. I have found several wire connections that were not very good (ring terminal way too large for the stud it went on, lots of corrosion, melted wire insulation) and I have been fixing them.

I believe the mower motors are good, when I get it going it is very quite and when it is disconnected all three turn very freely. In fact if I turn one blade by hand the two others start spinning as well from the current generated by the motor I'm turning.
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Re: PTO Contactor Problem

Postby mfrerking » Tue Jul 08, 2014 1:59 pm

I would continue checking for a wire in circuit that has a poor connection. One place to check is the connections on the PTO switch.

Also, if your pack voltage measurement is accurate, it is way low.

A fully charged 6-volt battery should measure 6.32 volts (37.92 pack voltage). At 50% discharge, it should measure 6.12 volts (36.72 pack voltage). At 75%, it should measure 6.03 (36.18 pack voltage). To get the longest life from your battery pack, try to maintain them above 50%. Consistently running the down below 75 - 80 % will take years off of their life span. Consistently running them down to dead will shorten their life span even more.
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Re: PTO Contactor Problem

Postby jtcweb » Tue Jul 08, 2014 2:10 pm

My "fuel" gauge always reads in the red so I will have to get that fixed as well. I'm not sure on the voltage number so I should check again after a period of mowing. It does read over 39V when fully charged. These are new batteries and this was the first time they really did anything. To date we just pulled some trailers around for a few minutes between charges.
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Re: PTO Contactor Problem

Postby Jeff Antonucci » Tue Jul 08, 2014 4:53 pm

I had an E-20 that did the same thing and was even burning up PTO contactors. I attributed it to weak batteries / low voltage. I seem to recall the original 40 yr old Guardian relays some times needed a full 36V to hold the contacts closed. I switched to the modern relays Jim sells on the electric tractor Store and have never had any issues with them since.
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