Electric fans
Le Mans Master
Joined: Apr 2011
Posts: 6,284
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From: Hermosa
Le Mans Master
Joined: May 2003
Posts: 8,877
Likes: 3,556
From: Fernandina Beach FL
2023 Restomod of the Year finalist
2020 C3 of the Year Winner - Modified
I like that switch mysixtynine posted. That'd be the proper way to control the fans with the AC.
Personally, I'd use the 3-relay 2-speed wiring method. Put 2 temperature switches in separated by a temperature band (for example a 195* and 200* switch) so the low speed comes on first then it jumps to high speed if you still need the extra cooling. Use the switch mysixtynine posted in parallel with the lower temperature switch to bring on the low speed fans.
It's a little extra wiring but the advantages are that the fans are quieter much of the time, you put less wear on the fans and the fans don't put such a large surge load on the electrical system when they come on which means you won't have stuff like the lights flickering at night and the relays will last longer.
Personally, I'd use the 3-relay 2-speed wiring method. Put 2 temperature switches in separated by a temperature band (for example a 195* and 200* switch) so the low speed comes on first then it jumps to high speed if you still need the extra cooling. Use the switch mysixtynine posted in parallel with the lower temperature switch to bring on the low speed fans.
It's a little extra wiring but the advantages are that the fans are quieter much of the time, you put less wear on the fans and the fans don't put such a large surge load on the electrical system when they come on which means you won't have stuff like the lights flickering at night and the relays will last longer.
triggerfan series parallel by richardhayes454, on Flickr
Race Director
Joined: Apr 2009
Posts: 19,294
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From: Charlotte NC
Instructor
Joined: Nov 2014
Posts: 183
Likes: 0
From: Belmont NC
St. Jude Donor '15
Dub: Just curious, what does it "normally" cost to add a vintage a/c system...parts/labor to a car that a/c wasn't factory. I realize every car is different because of age/wear-tear. and I am speaking of 69-72 small block. I don't want to break any rules here so PM me if that's acceptable.
Race Director
Joined: Apr 2009
Posts: 19,294
Likes: 2,754
From: Charlotte NC
Dub: Just curious, what does it "normally" cost to add a vintage a/c system...parts/labor to a car that a/c wasn't factory. I realize every car is different because of age/wear-tear. and I am speaking of 69-72 small block. I don't want to break any rules here so PM me if that's acceptable.
DUB
Race Director
Joined: Apr 2007
Posts: 11,152
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From: South Western Ontario
Not exactly but similar. You're not sticking to and standard wiring method - mixing coil polarities and not using the generally accepted 30 as input (ie power) and 87/87a as outputs (ie load) of the relay contacts. You have at least 1 extra diode, and probably 2 when you consider the temp switches and AC trigger are likely contacts which can't have backfeed problems.
Here's a link to a diagram of how I would wire it. It could have been a little cleaner looking if fan 2 was shown above fan 1 but it's still very nice.
http://www.914world.com/bbs2/uploads...1386372075.png
The green low speed goes to the lower temperature coolant switch and the AC pressure switch in parallel.
The blue high speed can go to another coolant switch with a little higher temperature rating.
Here's a link to a diagram of how I would wire it. It could have been a little cleaner looking if fan 2 was shown above fan 1 but it's still very nice.
http://www.914world.com/bbs2/uploads...1386372075.png
The green low speed goes to the lower temperature coolant switch and the AC pressure switch in parallel.
The blue high speed can go to another coolant switch with a little higher temperature rating.
Le Mans Master
Joined: May 2003
Posts: 8,877
Likes: 3,556
From: Fernandina Beach FL
2023 Restomod of the Year finalist
2020 C3 of the Year Winner - Modified
Race Director
Joined: Apr 2007
Posts: 11,152
Likes: 890
From: South Western Ontario
I've wired lots of stuff and I do it the RIGHT way and follow the accepted/recommended way to wire components. If someone wires up your diagram and uses relays with diodes on the coils they'll blow up the diodes inside 2 of the relays. Don't post your diagrams if you can't take the criticism.
I never bothered mentioning how it was silly to power 2 relay coils from the main power circuit when you already have a switch 12V source feeding the 1st relay. I would use a fused and ignition switched source for all 3 relay coils.
I never bothered mentioning how it was silly to power 2 relay coils from the main power circuit when you already have a switch 12V source feeding the 1st relay. I would use a fused and ignition switched source for all 3 relay coils.
Last edited by lionelhutz; May 13, 2015 at 12:22 AM.
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