6 volt relay on genset - Electronic Circuits Projects Diagrams Free

bryan1 · 17th May 2005, 07:55 AM

Hiya Guys,
Well after a day and a half of fault finding why my 15 kva gas driven genset wouldn't start I found the start/stop relay to have a blown coil. This is after changing the motor coil and condensor and touching up the points dizzy cap and rotor button with a bit of emery thinking one of those parts had expired
Looking at the coil I'm assuming it's a single pole double throw relay which is rated at 6 volt with a resistance of 15 ohms. As I'm not real fluent with relays I'll describe it the best I can to see if I'm correct in my assumption. When I say the relay is old I mean old, now the relay has a power and a negative wire one one level then on the upper level on each side is two wires on each side. Now one side engages the starter motor where the other side cuts the engine. But with only 2 wires to control the relay I reckon when starting the motor the polarity is positive engaging the first throw and when switching the motor off the polarity reversed engaging the second throw.
As the input is straight off a 12 volt truck battery I can't see any reason for not using a modern 12 volt relay to replace it.

If anyone would like to help me out on this I'll appreciate it as trying to find a qualified person to come and fix proved fruitless.

Cheers Bryan

Dean Huster · 17th May 2005, 12:20 PM

If it is truly a 6-volt relay operating on a 12-volt system, it's no wonder the coil is blown. Both overvoltage and undervoltage are relay killers, both causing high coil currents to be drawn, eventually burning out the coil. I'd definitely replace it with a 12-volt device.
Dean

eblc1388 · 17th May 2005, 01:51 PM

Quote:

Originally Posted by Dean Huster

Both overvoltage and undervoltage are relay killers, both causing high coil currents to be drawn, eventually burning out the coil.

Understand the first case but have trouble in visualising the undervoltage case. Why would a DC relay coil draws high current when its coil is connected to a lower voltage?

Can you explains a bit more?

williB · 17th May 2005, 06:53 PM

Quote:

Originally Posted by bryan1

Hiya Guys,
Well after a day and a half of fault finding why my 15 kva gas driven genset wouldn't start I found the start/stop relay to have a blown coil. This is after changing the motor coil and condensor and touching up the points dizzy cap and rotor button with a bit of emery thinking one of those parts had expired
Looking at the coil I'm assuming it's a single pole double throw relay which is rated at 6 volt with a resistance of 15 ohms. As I'm not real fluent with relays I'll describe it the best I can to see if I'm correct in my assumption. When I say the relay is old I mean old, now the relay has a power and a negative wire one one level then on the upper level on each side is two wires on each side. Now one side engages the starter motor where the other side cuts the engine. But with only 2 wires to control the relay I reckon when starting the motor the polarity is positive engaging the first throw and when switching the motor off the polarity reversed engaging the second throw.
As the input is straight off a 12 volt truck battery I can't see any reason for not using a modern 12 volt relay to replace it.

If anyone would like to help me out on this I'll appreciate it as trying to find a qualified person to come and fix proved fruitless.

Cheers Bryan

i would go with the new relay, how many connections are on top of the old one??
also how can you measure the resistance of the coil if it is burnt out?all the relays i have seen have a resistance of around 2 ohms..so if you are measuring 15 ohms it is blown.
a picture is worth a thousand words..
the two largest connections are for the starter motor..the two smaller ones activate the coil..or one connection if you count the case as ground..
single pole single through btw,it has a spring to return it to off condition when power is not activating it..

Someone Electro · 17th May 2005, 07:10 PM

yea how can an lover voltage burn an coil?

williB · 17th May 2005, 07:17 PM

what Dean probably means is that if the voltage is not high enough the relay may chatter leading to its early demise..

Someone Electro · 17th May 2005, 07:58 PM

oh making sparks and so destroing the electrodes.

bryan1 · 18th May 2005, 12:08 AM

Hiya Guy's
How I know it's a 6 volt 15 ohm relay it's written on the side of the coil. Eh Dean the relay looks like the original one and the genset is over 30 years old so a 6 volt relay isn't a problem running of 12 volts, and Willi as you say a picture is worth a thousand words rings true that's why I'm buying a new digital camera today as my old 100 k camera just doesn't cut the mustard on close up shots. Now after sleeping on the subject I reckon the relay is a normally open on the start side and a normally closed on the stop side but the worst part is I'll probablly have to import a relay as the land of Oz carries stuff all which is the norm. I mean trying to find an Onan dealer over here has proved fruitless so in my next post I'll include a photo and the model no. of the genset in the hope I can find a dealer where I can get some new parts as in a distributer cap and such. Anyway thats enough of me ranting so this evening I'll update this thread.

Cheers Bryan

ljcox · 19th May 2005, 01:39 AM

I would really like to help, I'm a bit far from Adelaide Hills.

You did not say how much current is being switched by the relay. That is really important if you want the contacts to last.

JayCar and Dick Smith both sell suitable relays and both have shops in SA. JayCar also sell sockets for the relays.

See www.jaycar.com.au and www.dse.com.au

Search JC for catalogue numbers SY-4068, SY-4070, SY-4069, SY-4074, SY-4075, SY-4042 & SY-4040.

Or DSE for catalogue number P 8035

Len

williB · 19th May 2005, 02:45 AM

http://www.onan.com/onan/service/loc...HomeBody.jsp.1
Bryan there are actually quite a few onan dealers in Australia..
if you select australia at the bottom of the page..it has a large list

bryan1 · 19th May 2005, 07:18 AM

Hi WilliB,
Eh mate thanks very much for the link, I'll give 1 of the SA dealers a ring in the morning, and thanks Lj for the cat no's for the jaycar site I'll check them out. But as far as the current required I've no idea but
I had a rep from a mining mob over today and he suggested just to take it down to Clipsal's and they will identify it and replace it with something compatible. I'm picking up a nu phone with a 1.3 meg camera builtin tonite so I'll take a photo of it as this relay probably belongs in a museam as it's that ancient.

Cheers Bryan

ljcox · 19th May 2005, 08:46 AM

Bryan,
I would take it to an auto electrician shop and see what they suggest.

Is it the relay that switches the starter motor? If so, it will have to switch a fairly large current.

Len

**Nigel Goodwin** · 19th May 2005, 08:52 AM

Quote:

Originally Posted by bryan1

Eh Dean the relay looks like the original one and the genset is over 30 years old so a 6 volt relay isn't a problem running of 12 volts

It certainly will be! - are you SURE it's fed from 12V, and there isn't a dropper resistor somewhere feeding it?.

Dean Huster · 19th May 2005, 10:34 PM

Yes, at first, it doesn't make sense that low voltage on a relay would cause problems. Like a motor, a relay draws more current when first pulling in than it consumes when fully activated.

Now, most of the problems with low voltage apply more to "honking" relays, e.g., contactors, motor starters, solenoids, etc. .... devices that are heftier. If the relay doesn't fully pull in, coil current can rise and cause overheating. As mentioned, chattering is a big problem, especially with AC coils as the chattering can beat the relay to pieces -- literally. Overvoltage can also beat the relay up by causing the armature to slam into place and then make the coil heat up with the extra current/power.

Dean

bryan1 · 20th May 2005, 03:09 AM

Hi Guys,
Well as WilliB said before a picture is worth a thousand words so instead of buyin a nu phone I went for a digi camera instead. So here's a pic of the electrical box. I've added a few details to the drawing and the voltages shown are on full time. I'm heading back to do a few more tracing and voltage tests so hopefully we can get ontop of it.

Cheers Bryan

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17th May 2005, 07:55 AM	(permalink)
bryan1	6 volt relay on genset Hiya Guys, Well after a day and a half of fault finding why my 15 kva gas driven genset wouldn't start I found the start/stop relay to have a blown coil. This is after changing the motor coil and condensor and touching up the points dizzy cap and rotor button with a bit of emery thinking one of those parts had expired Looking at the coil I'm assuming it's a single pole double throw relay which is rated at 6 volt with a resistance of 15 ohms. As I'm not real fluent with relays I'll describe it the best I can to see if I'm correct in my assumption. When I say the relay is old I mean old, now the relay has a power and a negative wire one one level then on the upper level on each side is two wires on each side. Now one side engages the starter motor where the other side cuts the engine. But with only 2 wires to control the relay I reckon when starting the motor the polarity is positive engaging the first throw and when switching the motor off the polarity reversed engaging the second throw. As the input is straight off a 12 volt truck battery I can't see any reason for not using a modern 12 volt relay to replace it. If anyone would like to help me out on this I'll appreciate it as trying to find a qualified person to come and fix proved fruitless. Cheers Bryan __________________ " The only way to avoid human error is to avoid the use of humans"

17th May 2005, 12:20 PM	(permalink)
Dean Huster	If it is truly a 6-volt relay operating on a 12-volt system, it's no wonder the coil is blown. Both overvoltage and undervoltage are relay killers, both causing high coil currents to be drawn, eventually burning out the coil. I'd definitely replace it with a 12-volt device. Dean __________________ Dean Huster, Electronics Curmudgeon Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines). R.I.P.

17th May 2005, 07:10 PM	(permalink)
Someone Electro	yea how can an lover voltage burn an coil? __________________ Il give you shocking experience.

17th May 2005, 07:17 PM	(permalink)
williB	what Dean probably means is that if the voltage is not high enough the relay may chatter leading to its early demise..

17th May 2005, 07:58 PM	(permalink)
Someone Electro	oh making sparks and so destroing the electrodes. __________________ Il give you shocking experience.

18th May 2005, 12:08 AM	(permalink)
bryan1	Hiya Guy's How I know it's a 6 volt 15 ohm relay it's written on the side of the coil. Eh Dean the relay looks like the original one and the genset is over 30 years old so a 6 volt relay isn't a problem running of 12 volts, and Willi as you say a picture is worth a thousand words rings true that's why I'm buying a new digital camera today as my old 100 k camera just doesn't cut the mustard on close up shots. Now after sleeping on the subject I reckon the relay is a normally open on the start side and a normally closed on the stop side but the worst part is I'll probablly have to import a relay as the land of Oz carries stuff all which is the norm. I mean trying to find an Onan dealer over here has proved fruitless so in my next post I'll include a photo and the model no. of the genset in the hope I can find a dealer where I can get some new parts as in a distributer cap and such. Anyway thats enough of me ranting so this evening I'll update this thread. Cheers Bryan __________________ " The only way to avoid human error is to avoid the use of humans"

19th May 2005, 01:39 AM	(permalink)
ljcox	I would really like to help, I'm a bit far from Adelaide Hills. You did not say how much current is being switched by the relay. That is really important if you want the contacts to last. JayCar and Dick Smith both sell suitable relays and both have shops in SA. JayCar also sell sockets for the relays. See www.jaycar.com.au and www.dse.com.au Search JC for catalogue numbers SY-4068, SY-4070, SY-4069, SY-4074, SY-4075, SY-4042 & SY-4040. Or DSE for catalogue number P 8035 Len

19th May 2005, 02:45 AM	(permalink)
williB	http://www.onan.com/onan/service/loc...HomeBody.jsp.1 Bryan there are actually quite a few onan dealers in Australia.. if you select australia at the bottom of the page..it has a large list

19th May 2005, 07:18 AM	(permalink)
bryan1	Hi WilliB, Eh mate thanks very much for the link, I'll give 1 of the SA dealers a ring in the morning, and thanks Lj for the cat no's for the jaycar site I'll check them out. But as far as the current required I've no idea but I had a rep from a mining mob over today and he suggested just to take it down to Clipsal's and they will identify it and replace it with something compatible. I'm picking up a nu phone with a 1.3 meg camera builtin tonite so I'll take a photo of it as this relay probably belongs in a museam as it's that ancient. Cheers Bryan __________________ " The only way to avoid human error is to avoid the use of humans"

19th May 2005, 08:46 AM	(permalink)
ljcox	Bryan, I would take it to an auto electrician shop and see what they suggest. Is it the relay that switches the starter motor? If so, it will have to switch a fairly large current. Len

19th May 2005, 10:34 PM	(permalink)
Dean Huster	Yes, at first, it doesn't make sense that low voltage on a relay would cause problems. Like a motor, a relay draws more current when first pulling in than it consumes when fully activated. Now, most of the problems with low voltage apply more to "honking" relays, e.g., contactors, motor starters, solenoids, etc. .... devices that are heftier. If the relay doesn't fully pull in, coil current can rise and cause overheating. As mentioned, chattering is a big problem, especially with AC coils as the chattering can beat the relay to pieces -- literally. Overvoltage can also beat the relay up by causing the armature to slam into place and then make the coil heat up with the extra current/power. Dean __________________ Dean Huster, Electronics Curmudgeon Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines). R.I.P.