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post #16 of 22 (permalink) Old Sep 4th, 19, 7:38 AM
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Re: Electric fan relays question...

I should clarify: Diodes across both the coil of the relay, to suppress the voltage spike generated when that is turned off, and also across the load (fan motor) would be good. The relay coil is an inductor, and thus generates a relatively high voltage spike when current through it is interrupted by turning it off. A DC motor is a bigger inductor, and so it generates an even bigger spike when the relay contacts open. THAT is what I was originally warning about-the voltage spike produced by opening the relay contacts will arc across them and ruin them, slowly. They gradually turn into a resistance heater.

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post #17 of 22 (permalink) Old Oct 8th, 19, 1:43 PM
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Re: Electric fan relays question...

Originally Posted by Dean View Post
Electrical connections get hot because they are not good enough connections.
I would agree that this is the most likely cause. Anytime I use crimp-on connector for high amp applications I also solder them. I try to use good quality American made connectors. Most are made in China now and of lower quality. Thinner and softer metal. A blade connector should have nice line contact on both sides and fit snug. The poorer quality ones contact on a point or two and feel loose. It's hit or miss with them.
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post #18 of 22 (permalink) Old Oct 8th, 19, 3:27 PM
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Re: Electric fan relays question...

The crimp connectors available in auto parts and big box stores are junk. The Sta-kon connectors by Thomas & Betts are the only ones I rely on. Panduit makes a decent line of connectors too. A ratcheting crimp tool is the proper way to ensure a good wire crimp to the connector. The relay and wire overheating are caused by poor connectors. The diode addition is worthwhile.
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post #19 of 22 (permalink) Old Oct 8th, 19, 4:43 PM
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Re: Electric fan relays question...

Wow guys. I've never given thought to the quality of connectors. They look good when properly crimped and sometimes soldered. Then there's the ones you heat up and I guess some kind of solder melts in them. any opinions on those?
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post #20 of 22 (permalink) Old Oct 8th, 19, 5:02 PM
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Re: Electric fan relays question...

Agreed on the T&B crimps.

I would advise against using a torch or flame to heat a crimp to solder them, the crimp will lose some of it's heat treatment and won't grab it's counterpart very well.

A good iron of 900~1,000 degrees works great.

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post #21 of 22 (permalink) Old Yesterday, 12:54 PM
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Re: Electric fan relays question...

I prefer to use uninsulated terminals as much as possible and use heat shrink to finish it. It makes things much cleaner than trying to use a plastic coated connector.

Ratcheting crimpers are great but keep an eye out for the cheap brands, their dies are terrible. I have one of the sets from Iwiss, the crimper seems but the die for uninsulated terminals had to be filed down and shimmed to actually give a good crimp. The open barrel die was better for GM terminals, but took some finessing.

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post #22 of 22 (permalink) Old Today, 6:31 AM
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Re: Electric fan relays question...

At work we have crimp connectors with heat shrink already on them. Pretty slick, but i bet we pay through the nose for them.
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