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Safety Switches?


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#1 SammyRye OFFLINE  

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Posted August 20, 2012 - 04:33 PM

Seems as tho there's been a lot of discussion lately about the 990's being hard to start and having to fiddle with the ignition system, and on and on.

On both of my 990's, there are 2 safety switches - one on the brake and one on the mid-PTO. Do these switches also contain a resistor? I know a lot of guys just bypass the switches (done it myself), and the system seems to work - but, if there's a resistor in there, may that also contribute to hard / no-start issues?

Thanks for your input,
Rich

#2 JDBrian OFFLINE  

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Posted August 20, 2012 - 05:18 PM

They don't contain a resistor . It's just a switch. However when they get old they can develop enough resistance due to corrosion and wear to cause problems with the starting circuit. The extra resistance causes a voltage drop and at some point there isn't enough current flowing to bring in the solenoid. This can also be a problem in old ignition switches. I recently repaired both the ignition switch and the safety switches for my MF8. Heres links to some pictures of both repairs if you're interested.
http://gardentractor...tch#entry153458
http://gardentractor...tch#entry152862
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#3 New.Canadian.DB.Owner OFFLINE  

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Posted August 20, 2012 - 06:50 PM

I had a similar problem with the safety switches on my John Deere STX38. There is a mod you can do that inserts a relay before the solenoid. The lower voltage left after the dirty safety switches is enough to hold the relay closed. The relay dumps battery voltage directly onto the solenoid. I posted a diagram in the John Deere forum:

http://gardentractor...138-wont-start/
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#4 SammyRye OFFLINE  

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Posted August 20, 2012 - 06:54 PM

Thanks, Brian :thumbs:

That's what I was thinking - just a switch. Ok, so then I can disconnect without causing a problem.

Thanks again,
Rich

#5 JDBrian OFFLINE  

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Posted August 20, 2012 - 07:10 PM

Rich, You would need to connect the wires together that normally connect to the switch to simulate the switch being closed.

Thanks, Brian :thumbs:

That's what I was thinking - just a switch. Ok, so then I can disconnect without causing a problem.

Thanks again,
Rich


The problem is that you no longer have the safety function provided by the switch!




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