6volt starter relay?

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William Block
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Re: 6volt starter relay?

#31 Post by William Block »

Joe Leoni's and Tony's relays are the same -- Joe built Tony's. However the amperage to the starter will be higher with Joe's relay since it taps into the heavy heavy wire coming directly from the battery rather than the starter switch, supplied by a much smaller cable
bill

"Joe's" relay instock at www.blocks-books.com
Bill Block
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Norm Miller
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Re: 6volt starter relay?

#32 Post by Norm Miller »

John Hearn,

The problem is voltage drop at the solenoid "relay" and it will not fire with less than 5.6v.
When hot the resistance increases causing further voltage drop.
The external relay acts as a foot valve holding the initial voltage from the ignition switch.
Another option is to bring a new #30 wire directly to the ign. switch bypassing the light switch.

Happiness is not old wire with corroded ends.

Norm
 

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Dave Wildrick
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Location: Houston, TX

Re: 6volt starter relay?

#33 Post by Dave Wildrick »

William Block wrote:Joe Leoni's and Tony's relays are the same -- Joe built Tony's. However the amperage to the starter will be higher with Joe's relay since it taps into the heavy heavy wire coming directly from the battery rather than the starter switch, supplied by a much smaller cable
bill
Point taken and Sebastian had it partly right (about possibly being better to mount the relay at the starter).
So, it's "water pipe" logic. The size of the cable (pipe) supplying the electricity to the solenoid terminal is much larger when the feed to the relay is from the much larger gauge wire coming directly from the battery, which translates into more amps and less voltage loss.

For me, I guess the question really is "How many amps (at more than 5.6V) does the starter solenoid need to receive at ignition in order to work properly?" Or "How much better is it to connect the relay next to the starter than at the ignition switch?"

Oddly enough, in both of my C coupes, the relays are located at the starter because I installed them before I ever heard of Tony's much easier to install setup.
Dave Wildrick
Houston, TX
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Jim Alton
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Re: 6volt starter relay?

#34 Post by Jim Alton »

Norm Miller wrote:John Hearn,

The problem is voltage drop at the solenoid "relay" and it will not fire with less than 5.6v.
When hot the resistance increases causing further voltage drop.
The external relay acts as a foot valve holding the initial voltage from the ignition switch.
Another option is to bring a new #30 wire directly to the ign. switch bypassing the light switch.

Happiness is not old wire with corroded ends.

Norm
I think the hard start relay at the starter has some advantages:

According to a wiring diagram the wire from the ignition switch to the solenoid is 4 mm² roughly 11 AWG (which apparently exists but I've never seen any).

A handy online wire resistance calculator gives a resistance for 10 feet of 11 AWG wire as 0.013 Ω.

The relay I installed in my car had a 20 A fuse and it kept blowing so I went to 30 A fuse.

Guessing the current to energize the solenoid is maybe 25 A (maybe there's something wrong with my starter but it did blow 20 A fuses), running that current through 0.013 Ω will drop 0.325 V.

So, if you drop 0.325 V just in the wire between the ignition switch and the solenoid on top of the drop from the battery's internal resistance and all the other non-superconducting bits you may easily get below 5.6 V.
 
Jim Alton
Los Angeles County, CA
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M Penta
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Re: 6volt starter relay?

#35 Post by M Penta »

John Hearn wrote:Every 356 starter has a "relay" it's called the solenoid......
KTF
John
Yes but the solenoid can draw over 30A, compared to mA's for the relay. I installed the relay only to protect the (expensive) 50 yr old ignition switch, which works fine and I would like to keep it that way.....

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