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dual fan relay

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=132193
Printed Date: May 15, 2025 at 12:47 PM


Topic: dual fan relay

Posted By: bobv
Subject: dual fan relay
Date Posted: September 15, 2012 at 4:19 AM

I just installed dual 12" fans. here is how they are wired two relays 1st 30 12v hot ,86 12 v ignition ,87 to fan + ,85 jumps to 2nd relay 87 then to switch, 86 on 2nd relay to ac +30 and 85 on 2nd relay to ground. This pops the 30 a fuse as soon as the switch is on this works fine with one fan, when both fans are used the fuse pops. These fans came wired this way It seems there is too much draw for two fans with a 30 a fuse. Any suggestions?
Thanks
Bob



Replies:

Posted By: oldspark
Date Posted: September 15, 2012 at 2:29 PM
There is something wrong with that wiring as described.

How do you want the fans switched?
IE - either or both on or #1 else #1 & #2, and then with IGN, or IGN & switch, or IGN & temp switch or manual switch, one switch for each (or #1 for Fan1, #2 for Fan 1&2)?


I'd argue the grounded fans to their own relay (87) with power (30) to individual fuses near the battery +12V.

The relays can then be controlled as required. Connect (or reconnect later) their coils (85 & 86) to IGN+12V or +12V and GND thru whatever switches - maybe using diodes for one switch to turn both on...




Posted By: bobv
Date Posted: September 15, 2012 at 4:36 PM
Believe it or not I replaced the Chinese fuse with a quality one and all works no issues!
This relay setup came wired this way from be cool it is supposed to run two fans.
Sorry I didn't mention the application it is going in a 1969 corvette. Right now both fans come on at the same time through a temp switch they draw 25 amps for the pair . Is it possible to delay the start of the second fan so that start up is less demanding without re doing the relays?
Thanks for your reply!
Bob




Posted By: oldspark
Date Posted: September 15, 2012 at 7:40 PM
The new fuse is probably Chinese too, but yes, aftermarket systems often cut costs.

A delay between the first & 2nd relay. Maybe a 528T (others can advise) or search the12volt for delay circuits (eg, Hotwaterwizard).





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