series and parallel using relays

Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=124288
Printed Date: May 09, 2025 at 7:26 PM

Topic: series and parallel using relays

Posted By: nick_88
Subject: series and parallel using relays
Date Posted: November 05, 2010 at 5:44 AM

Hi guys, im trying to figure out how to wire up my thermo fans in my car, so that on 'Low speed' both fans are wired in series so they are getting 6v each, and when high speed is activated(via computer or manual overide switch) they are wired in parallel and recieve 12v each.

I think ive worked it out, just looking for clarification and/or possible other ways to wire it with more/fewer relays

Any help appreciated

Heres my diag so far...
posted_image

Please excuse the crude drawing and my handwriting! haha

Replies:

Posted By: nick_88
Date Posted: November 05, 2010 at 5:47 AM

also just incase you cant read my writing, when the Low speed is active, only it has power. But when High speed is active both Low/High wires have power, i can easily change this to just Low - Low, High - High if need be to make it easier

Posted By: nick_88
Date Posted: November 05, 2010 at 5:58 PM

anybody??

Posted By: stevdart
Date Posted: November 05, 2010 at 10:39 PM

https://www.the12volt.com/relays/page5.asp#spvr

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Posted By: dualsport
Date Posted: November 13, 2010 at 8:24 AM

That looks like how I'd imagine a doctor would draw a schematic-

Did you try out the fans in series to see if they're doing anything useful that way? It might be like fans in movies that spin more for visual effect than cooling. The slower the fans spin in the movies, the hotter it's supposed to be, especially when interrogating the suspect- posted_image

Posted By: oldspark
Date Posted: November 14, 2010 at 5:02 AM

It must be a high current diode.
I wonder what it is for?