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Car Forum / Jeep / January 2004

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relay for offroad lights?

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Jet - 29 Jan 2004 00:51 GMT
I have a set of 150 watt 385,000 candle power KC offroad lights on my jeep
and I melted a 30 amp relay. it was a $6 relay I bought at the auto parts
store that the guy insisted would work. so what you guys are using? also my
brother in-law has 4 of same lights on his off roader and is also having
problems finding a relay that works on the 4 lights. any suggestions?
thanks carmine
DougW - 29 Jan 2004 00:25 GMT
Jet did pass the time by typing:
> I have a set of 150 watt 385,000 candle power KC offroad lights on my jeep
> and I melted a 30 amp relay. it was a $6 relay I bought at the auto parts
> store that the guy insisted would work. so what you guys are using? also my
> brother in-law has 4 of same lights on his off roader and is also having
> problems finding a relay that works on the 4 lights. any suggestions?
> thanks carmine

Your going to have to go to a local electronics parts store.

150W @ 12V = 12.5A but that's not counting warmup draw

The cheap solution, run one relay per light.

Signature

DougW

L0nD0t.$t0we11 - 29 Jan 2004 03:39 GMT
Roughly 1/28/04 16:25, DougW's monkeys randomly typed:

> Jet did pass the time by typing:
>> I have a set of 150 watt 385,000 candle power KC offroad lights on my jeep
[quoted text clipped - 5 lines]
>
> Your going to have to go to a local electronics parts store.

 Or try MCM Newark at www.mcmelectronics.com

> 150W @ 12V = 12.5A but that's not counting warmup draw

 I'd go for something like a 25 Amp relay at 12 volts for that
 and think seriously about mercury wetted contacts.

> The cheap solution, run one relay per light.

 With the added advantage you never lose both.

 Bosch makes some heavy duty ones, but PITA to use as they
 are socketed.

Signature

Now that Spirit Rover has confirmed the presence of weapons of
mass destruction on Mars, we are preparing to invade...

Jerry Newton - 29 Jan 2004 12:03 GMT
Good point, Lon, on the Bosch relays.  They are socketed, but you can buy
the socket prewired, so all you have to do is cut and splice.  In my
opinion, there is a reason that the major manufacturers use Bosch relays.
There are dozens on any given car, and they generally last the life of the
vehicle.

Jerry

> Roughly 1/28/04 16:25, DougW's monkeys randomly typed:
>
[quoted text clipped - 25 lines]
> Now that Spirit Rover has confirmed the presence of weapons of
> mass destruction on Mars, we are preparing to invade...
Paul Calman - 29 Jan 2004 17:12 GMT
> Good point, Lon, on the Bosch relays.  They are socketed, but you can buy
> the socket prewired, so all you have to do is cut and splice.  In my
> opinion, there is a reason that the major manufacturers use Bosch relays.
> There are dozens on any given car, and they generally last the life of the
> vehicle.

I just plug in connectors without sockets. I get 6 or more of them for free
from every european car I see heading for the scrap yard. BMW's Bosch relays
have the terminals in the same configuration, but are wired differently, but
have the schematic on the case.
Signature

Paul Calman, Hathaway Pines, California

L0nD0t.$t0we11 - 29 Jan 2004 18:12 GMT
Roughly 1/29/04 09:12, Paul Calman's monkeys randomly typed:

>> Good point, Lon, on the Bosch relays.  They are socketed, but you can buy
>> the socket prewired, so all you have to do is cut and splice.  In my
[quoted text clipped - 6 lines]
> have the terminals in the same configuration, but are wired differently, but
> have the schematic on the case.

 And I definitely forgot to mention that they are readily
 available at any junkyard, having been used since at least
 the mid-70s on Porsche, VW, etc.  Often a nice rack of them
 is available in the engine compartment.

 The one for the fan on an old Porsche or VW is easily strong
 enough, but I never observed any difference in rating marked
 on that one compared to the fuel pump relay or such.  Just
 be sure the schematic markings are still there, and you can
 get the socket out of the panel on the old early 70's
 fuel injected porsche, vw, etc if you want it in the event
 the relay has to be changed.

 If you go MCM Newark or a local electronics distributor,
 stick to metal cased relays, not the cheap plastic ones.
 A continuous duty high current relay is best, and mercury
 wetted altho politically incorrect, does cut the contact
 resistance enough to avoid heating.

Signature

Now that Spirit Rover has confirmed the presence of weapons of
mass destruction on Mars, we are preparing to invade...

L.W.(=?iso-8859-1?Q?=DFill?=) Hughes III - 29 Jan 2004 18:38 GMT
    I have bought several Sylvania fog light sets, and never have they
included the socket. Their relays have looked exactly like what Radio
Shack sells: http://www.billhughes.com/relay.jpg 
       God Bless America, ßill O|||||||O
mailto:LWHughes3rd@aol.com

> > Good point, Lon, on the Bosch relays.  They are socketed, but you can buy
> > the socket prewired, so all you have to do is cut and splice.  In my
[quoted text clipped - 8 lines]
> --
> Paul Calman, Hathaway Pines, California
Mike Romain - 29 Jan 2004 00:28 GMT
Most folks use one relay per light.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

> I have a set of 150 watt 385,000 candle power KC offroad lights on my jeep
> and I melted a 30 amp relay. it was a $6 relay I bought at the auto parts
> store that the guy insisted would work. so what you guys are using? also my
> brother in-law has 4 of same lights on his off roader and is also having
> problems finding a relay that works on the 4 lights. any suggestions?
> thanks carmine
L.W.(=?iso-8859-1?Q?=DFill?=) Hughes III - 29 Jan 2004 00:40 GMT
    Where was your fuse? Maybe increase the size of the wire from the
battery, so resistance heat won't be your problem:
http://www.kchilites.com/faq.html
http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/relay.htm
Maybe, use two Japanese relays, one for each light.
       God Bless America, ßill O|||||||O
mailto:LWHughes3rd@aol.com http://www.billhughes.com/

> I have a set of 150 watt 385,000 candle power KC offroad lights on my jeep
> and I melted a 30 amp relay. it was a $6 relay I bought at the auto parts
> store that the guy insisted would work. so what you guys are using? also my
> brother in-law has 4 of same lights on his off roader and is also having
> problems finding a relay that works on the 4 lights. any suggestions?
> thanks carmine
Jet - 29 Jan 2004 23:18 GMT
I had 2 fuses on the lights about 4 inches away from the battery. i had a 25
amp on the light side and a 3 amp on the switch side the 25 amp fuse was
blown but it didn't blow until the relay was burt to a crisp. I guess their
30 amp rating was a little off. I will try running 2 relays. all the wires
that I used was supplied by k.c. in the kit with the lights. the original
k.c. relay in the kit looked identical to the one I put in there the only
reason I changed it is because one of the terminals corroded off.

the kc relay lasted 2 years

 thanks carmine

>      Where was your fuse? Maybe increase the size of the wire from the
> battery, so resistance heat won't be your problem:
[quoted text clipped - 10 lines]
> > problems finding a relay that works on the 4 lights. any suggestions?
> > thanks carmine
Lee Ayrton - 29 Jan 2004 23:22 GMT
"...because one of the terminals corroded off." -- there's your problem.
It wasn't that the relay melted because you were pulling too much current
through it, it was that the terminals you connected to it were rusty.  A
connection that isn't bright and clean will have resistance, resistance
causes heat, heat encourages more corrosion.  The _connection_ got hot and
the heat melted the plastic base of the relay.  If you reuse those
connectors it will fail again.  Cut the wires back until you have bright
copper, put on new terminals and pack them with bulb grease before you
reconnect them.

> I had 2 fuses on the lights about 4 inches away from the battery. i had a 25
> amp on the light side and a 3 amp on the switch side the 25 amp fuse was
[quoted text clipped - 25 lines]
> > > problems finding a relay that works on the 4 lights. any suggestions?
> > > thanks carmine
Rich Hampel - 30 Jan 2004 02:49 GMT
NEVER EVER use 'automotive' grade connectors on **anything** that has
large current draw .... they will ALWAYS corrode and eventually give
high resistance, etc. then fail !!!!!!! When the **crappy** automotive
connectors develop high resistance due to corrosion, etc. the current
draw goes UP when the voltage goes DOWN due to the resistance, when the
current goes UP the plastic componentry softens, etc.

BETTER is to use pre-tinned 'marine grade' crimp connectors and marine
grade pre-tinned wire.  .... use on EVERYTHING, dont use the crappy
automotive grade crimp connectors if you dont want to replace every
damn year because of oxidation/corrosion.

Use marine grade crimp connectors and wire .... and then seal with
vinyl heat shrink tube with a bit of dielectric grease inside and then
coat with liquid vinyl (liquid tape).   Dont even think about
soldering!
www.westmarine.com. etc.  - bring your fatted wallet.

> "...because one of the terminals corroded off." -- there's your problem.
> It wasn't that the relay melted because you were pulling too much current
[quoted text clipped - 35 lines]
> > > > problems finding a relay that works on the 4 lights. any suggestions?
> > > > thanks carmine
Rich Hampel - 30 Jan 2004 02:56 GMT
Good article on corrosion/oxidation proof wiring techniques:  
http://www.sailnet.com/collections/articles/index.cfm?articleid=brigno00
01%20%20&tfr=fp

ENJOY !!!!!  

> NEVER EVER use 'automotive' grade connectors on **anything** that has
> large current draw .... they will ALWAYS corrode and eventually give
[quoted text clipped - 58 lines]
> > > > > problems finding a relay that works on the 4 lights. any suggestions?
> > > > > thanks carmine
JimG - 29 Jan 2004 01:23 GMT
Could have been bad connections at the relay.  Where did the relay melt...
at the terminals?  As DougW says 12.5 amps each but that is pushing the
limit of a $6 relay.  And to Bill's point, if you have less than 12 volts at
the relay, the current goes up and then you approach the "30 amp rating" of
the relay.  You could use a starter solenoid.

--
JimG
80' CJ-7 258 CID
35" BFG MT on 15x10 Centerlines
D44 Rear, Dana 30 Front. SOA
4.56 Gears, LockRight F&R
Dana 300 w/4:1 & Currie twin sticks
Warn X8000i w/ dual batteries

> I have a set of 150 watt 385,000 candle power KC offroad lights on my jeep
> and I melted a 30 amp relay. it was a $6 relay I bought at the auto parts
> store that the guy insisted would work. so what you guys are using? also my
> brother in-law has 4 of same lights on his off roader and is also having
> problems finding a relay that works on the 4 lights. any suggestions?
> thanks carmine
Barry R. - 30 Jan 2004 04:55 GMT
I use a starter relay from an old 60's car to do my 2 KC 385,000 CP
lights.  I  saw this setup on an old bronco that a freind of mine
bought back in high school, and it was a hell of an idea.  When I flip
the light switch I hear a the clunk of the relay designed to channel
hundreds of amps and my lights come on.  When I turn it off another
click.  I've had this setup for 6 years with no problems on my CJ.
Only thing strang is when someone is looking under the hood and says
"WTF you've got to started solenoids!!"    I can take a picture of the
setup if your interested.  It is pretty easy to setup.

>I have a set of 150 watt 385,000 candle power KC offroad lights on my jeep
>and I melted a 30 amp relay. it was a $6 relay I bought at the auto parts
>store that the guy insisted would work. so what you guys are using? also my
>brother in-law has 4 of same lights on his off roader and is also having
>problems finding a relay that works on the 4 lights. any suggestions?
>thanks carmine
Robert Bills - 30 Jan 2004 15:43 GMT
>I use a starter relay from an old 60's car to do my 2 KC 385,000 CP
>lights

I prefer a constant-duty solenoid over a starter solenoid.  Starter solenoids
can "pop" when they get hot from constant use  and then you're in the same boat
as with a cheap relay - no power.

Constant duty solenoids are commonly used for running a charging wire to a
trailer or camper battery (only "on" when ignition is on so you won't draw down
your starting battery), which I think is a good feature for high-draw offroad
lights.  They are a few dollars more than a starter solenoid, but worth it.
Available at any good auto parts counter, NAPA, trailer supply stores, etc.



Robert Bills
KG6LMV
Orange County CA

http://www.outdoorwire.com/4x4/jeep/home/jeep-l/billsr.htm
http://www.RobertBills.com
CRWLR - 30 Jan 2004 18:52 GMT
Well, the quick math says that one 150W bulb at 12V will draw 12.5A. If your
brother has 4 lamps at 12.5A each, then he is drawing 50A through a 30A
relay. My guess is this will melt.

> I have a set of 150 watt 385,000 candle power KC offroad lights on my jeep
> and I melted a 30 amp relay. it was a $6 relay I bought at the auto parts
> store that the guy insisted would work. so what you guys are using? also my
> brother in-law has 4 of same lights on his off roader and is also having
> problems finding a relay that works on the 4 lights. any suggestions?
> thanks carmine
 
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