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Author
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Topic: polarity
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mikeR
True Blue Posts: 102
From: exeter,devon,england
Registered: May 2003
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posted March 16, 2006 12:40
   
hi chaps,
Been a bit quiet because i've had to do 6 months hard labour on the house.
When i bought my dexta its wiring was badly fried, I treated it to a new loom last year all was well for a while then it fried that as well.
It was suggested that the polarity of the dynamo might be wrong?
Any other thoughts/checks?
How do I check/change the polarity there is an earlier post which talks about temp feeds etc but it is not clear - to me at least - which way round it is refering to.
The battery is a +ve earthIP: Logged |
Brian
Rules All Things Blue Posts: 2824
From: United Kingdom
Registered: Feb 2002
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posted March 17, 2006 08:29
Mike,
You can not check it but it is dead easy to change. With the dynamo fitted but not wired, take a wire from the live side of the battery and hold it to the field terminal for about 10 secs.Job done! ------------------
Kind regards
Brian IP: Logged |
Mike Kuscher
True Blue Posts: 123
From: Worcestershire, England
Registered: Oct 2002
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posted March 17, 2006 11:25
Mike, Brian,To check polarity of generator... Disconnect the two wires, from the spade terminals on the back of the generator.
Link them together with a piece of wire.
Take an analogue (not digital) volt meter.
Connect the POSITIVE lead to the chassis of the tractor. Connect the NEGATIVE lead to the wire connecting the two terminals on the generator and start her up and rev to 1000 rpm.
If polarity correct, you should get approx. +24 volts. If polarity wrong, needle of meter will try to go to the left, off the scale. If substancially less than +24 volts, generator faulty (yes, 24 volts, regulator drops it to about 14 volts for charging).If polarity wrong, 'flash' the field windings, as Brian describes, to change polarity. Regards,
Mike
IP: Logged |
donhwyo
True Blue Posts: 54
From: Jackson Wy. USA
Registered: Nov 2002
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posted March 17, 2006 19:56
You can check with out shorting the wires also. The output will probably be about a half volt. This comes from the field in the housing being a magnet and the armature spining in it. Polarising is what sets up this feild. It can be setup either positive or negative. I can't think of any way it would change in normal operation. Even if you hooked up the battery backwards. Hooking the battery up backwards would probably burn up the wires if it was running but i think the regulator would stop that. Burnt wires are usualy due to a short to ground.Don IP: Logged |
mikeR
True Blue Posts: 102
From: exeter,devon,england
Registered: May 2003
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posted April 11, 2006 10:48
Morning,
As a none engineer - What exactly is the field terminal??? I don't want to cause more problemsIP: Logged |
Brian
Rules All Things Blue Posts: 2824
From: United Kingdom
Registered: Feb 2002
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posted April 11, 2006 10:50
The smaller of the two on the back of the dynamo------------------
Kind regards
Brian IP: Logged |
mikeR
True Blue Posts: 102
From: exeter,devon,england
Registered: May 2003
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posted April 11, 2006 11:18
Thanks - i am off to the shed to treat the little dear to some TLC and to enjoy myselfIP: Logged |
ger-man
True Blue Posts: 280
From: Germany
Registered: May 2003
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posted June 12, 2006 23:32
Guys,
just a silly question:
What happens to the starter motor and the voltage regulator when I change the polarity to negativ ground?------------------
Best Regards
Stefan
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www.fordson-dexta.de IP: Logged |
jmixigo
True Blue Posts: 14
From: Lanett, Alabama-USA
Registered: Jun 2006
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posted June 14, 2006 06:00
Reverse polarity to the armature tries to reverse it's rotation; reverse polarity to the starter field coils tries to reverse rotation. Reverse plus reverse equals normal rotation with either electrical polarity.
Don't ever reverse polarity to the regulator unless you WANT to fry the wireing. Most starters recieve reversed polarity when the tractor is modified with an internally regulated alternator replacing the generator and regulator.------------------
jimmy mixon IP: Logged |
jomoon568
True Blue Posts: 61
From: Anglesy, N.Wales
Registered: Nov 2005
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posted June 14, 2006 11:36
MikeR,
At what position are you at now and Do you have the correct Wiring Daigram for the tractor. Also from the replys do you have an old AVO or DVM available as this may have to be wired up slowly by testing every connection out throughly.
1 Burnt loom
2 New loom
3 Between 1 & 2Regards
gaffer1
You can email me for a faster response
IP: Logged |
ger-man
True Blue Posts: 280
From: Germany
Registered: May 2003
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posted June 15, 2006 21:18
Guys,
thanks to all for your answers. Please let me ask if the following steps are correct:Step 1: Dynamo must be fitted but not wired.
Step 2: Connect the battery with negativ (-) to ground and positiv (+) to the wiring loom.
Step 3: Take a wire from positive (+) of the battery to the field terminal (the smaller terminal marked with the letter "F") for about 10 sec.
Step 4: Rewire the dynamo to the loom. Would be great if anybody of you can confirm this. Thanks. ------------------
Best Regards
Stefan
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www.fordson-dexta.de IP: Logged |
Brian
Rules All Things Blue Posts: 2824
From: United Kingdom
Registered: Feb 2002
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posted June 15, 2006 23:12
Yes that's correct Stefan. The output terminal on the battery goes to the "F" terminal for around 10 secs.Output terminal is the one not connected to earth. It could be + or - depending on your system. ------------------
Kind regards
Brian IP: Logged |
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