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Old 12-02-2012, 10:55   #1
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Wire Gauge

i have a bosch 40amp, 5 terminal relay to run a 30 load. i'm using #8 wire to the relay but the relay has slip on connectors and #8 wire won't work. how do you get around this problem? i've never saw a #8 female slip on connector.
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Old 12-02-2012, 11:46   #2
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Re: wire gauge

What are you running? and is it continious or momentary use (Like a glow plug)
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Old 12-02-2012, 11:53   #3
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Re: wire gauge

I assume the crux of the problem is finding 8 AWG female connectors -- correct?

Do you have room to solder your connections in place?
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Old 12-02-2012, 11:56   #4
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Re: wire gauge

it's a continuous load. my main question has to do with the #8 wire on the relay. it could be any load if you calculate voltage drop, the 8 wire has to be used.
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Old 12-02-2012, 12:09   #5
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Re: wire gauge

Use #8 to #10/12 step down butt connectors using short lengths of the smaller wire for connection to the relay.

Eric
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Old 12-02-2012, 12:11   #6
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Re: wire gauge

Strip back the #8 wire and then cut off about 1/3 of the strands at the insulation.

David
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Old 12-02-2012, 12:19   #7
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Re: wire gauge

Show us the relay and what you are trying to run.
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Old 12-02-2012, 12:20   #8
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Re: wire gauge

if i step down from a 8 to a 10 gauge then the 10 gauge won't be big enough for the amperage, or am i missing something.
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Old 12-02-2012, 12:28   #9
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Re: wire gauge

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Originally Posted by tuberider View Post
if i step down from a 8 to a 10 gauge then the 10 gauge won't be big enough for the amperage, or am i missing something.
Depends on wiring method and insulating rating but typically, 10 gauge wire rated for 105C not bundled, sheathed or in conduit and outside of engine space can handle 60 amps. The very short lengths needed for the transition would not affect voltage drop calculations.

Eric
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Old 12-02-2012, 12:41   #10
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Re: wire gauge

You can't get a push connector for an 8awg to a 1/4" bosch. You're not giving enough information as to what you are trying to do.
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Old 12-02-2012, 12:42   #11
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Re: wire gauge

Pictures work great for this kind of question.

How about one of these.

Dorman 86167 - Dorman Wiring Connectors - Overview - SummitRacing.com
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Old 12-02-2012, 12:52   #12
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Re: wire gauge

You can step down using a step-down-connector as suggested or you can just cut off a few strands of the 8AWG so that the remaining strands will fit into the connector you use.

The length of this interface is so short that it has no practical effect on your gauge calculations or voltage drop.
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Old 12-02-2012, 14:38   #13
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Re: wire gauge

The standard Bosch type relay uses a 1/4" qd fitting aka "faston" fitting. I don't think you'll find those in 8g crimps.

Don't confuse the carrying capacity of the wire or relay, with the need to use heavier cable to prevent voltage losses. If a 30A relay is sufficient for the job, and you are only using 8G cable to prevent voltage losses in the cable run, then there is no reason to worry about putting a smaller fitting on the end of the 8G wire so it can plug into the relay. You can indeed trim back, unstrand, some of the 8G cable until it fits into a 10-12G "yellow" faston crimp. That may not be ideal because the heavy cable may tend to pull out the connection from the relay. A better way is to buy a relay SOCKET, which has wires pigtailed into it, and then connect the 8G cable to the pigtail.
Last time I checked, all of these relays had cheaped out and they now are usually constructed by passing the contact through the casing and forming part of the relay with the same piece of metal. As the relay ages and the contacts wiggle loose in the plastic, they can cause the contact to open internally, inside the relay case, when the heavy wire pulls on the external contact. So a relay socket is highly advised unless you really ensure the heavy cable leads are stress relieved and secured.
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Old 12-02-2012, 15:06   #14
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Re: wire gauge

thanks for the replies. i'll look into a prewired socket that plugs into a typical bosch relay.
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Old 12-02-2012, 15:24   #15
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Re: wire gauge

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Originally Posted by hellosailor View Post
... A better way is to buy a relay SOCKET, which has wires pigtailed into it, and then connect the 8G cable to the pigtail.....
Duh -- I should have thought of that -- the relays used by my charging system are all installed in relay sockets. Good solid way to do it and I have never had any issues with this installation in over 10 years.
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