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Old 05-21-2020, 12:42 PM
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92GTA 92GTA is offline
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Default Do I still need a relay when using a thermal switch?

I am using this thermal switch for a fan on one of my fluid coolers: https://www.improvedracing.com/therm...00f-p-831.html


I'm so used to wiring up relays w/fuses to control electric fans (like for coolant radiators that draw 20+ amps), I didn't think that perhaps in the case of this thermal switch, that I may not need it.


The fan I'm controlling only draws 7.2 amps, that switch is rated for 10 amps.


Does this mean I don't need the relay in this case? I have a 25 amp continuous relay with a 30 amp fuse on hand, but if I can simplify my wiring, I'd like to. But on the other hand, if using a relay will make the strain easier on my electrical when it kicks on, then I'd rather go that route.


Thanks!

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Last edited by 92GTA; 05-21-2020 at 12:57 PM.
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Old 05-21-2020, 05:36 PM
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Use the thermal switch as the switch to turn the fan relay on.
You need the main power to go to the fan from the relay.



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Old 05-21-2020, 05:37 PM
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So wire it as normal with a relay. Understood.

Thanks!

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Old 05-22-2020, 05:38 AM
Geoff Geoff is offline
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You don't need a relay. The current capability of the switch is higher than the load, so safe to use the sw without a relay.

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Old 05-22-2020, 07:57 AM
"QUICK-SILVER" "QUICK-SILVER" is offline
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Quote:
Originally Posted by Geoff View Post
You don't need a relay. The current capability of the switch is higher than the load, so safe to use the sw without a relay.
The OP didn't post fan start-up amps.

Relays are cheap and easy to replace when their contacts get used up.

Clay

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Old 05-22-2020, 09:04 AM
Paul E Paul E is offline
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Quote:
Originally Posted by "QUICK-SILVER" View Post
The OP didn't post fan start-up amps.

Relays are cheap and easy to replace when their contacts get used up.

Clay

Yes this is correct


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Old 05-22-2020, 12:08 PM
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Quote:
Originally Posted by "QUICK-SILVER" View Post
The OP didn't post fan start-up amps.

Derale doesn't publish those in their specs so I have no clue.



Better safe than sorry then with the relay.

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Old 05-22-2020, 12:28 PM
Paul E Paul E is offline
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You said you already have a relay check around as there are many ways to mount the relay individually or in a multi relay mounted application. I did this in my 70 Lemans and mounted the unit in the inner fender behind the battery. Very easy to get to and I really removed all electrical draw from the original harness to the relay box for the horn hi and low beam, AC compressor clutch, coil, starter solenoid and blower fan. I am really happy with it. It did take some time and a lot of thought and layout. I purchased the wire termination ends so I could cut the wires to the correct length and terminate them instead of multiple splices. Is it over kill? YES it is!
Good luck.
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Old 05-22-2020, 12:31 PM
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Nice. I have all of mine attached to the top of my radiator support facing forward. Hidden and easy to get to by just removing that 1 metal closeout panel. I also have a dedicated body ground going to the radiator support for that reason.

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