Electric Gurus! - Gen 1 Condenser Fan Mod

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Electric Gurus! - Gen 1 Condenser Fan Mod

Postby furiousbob » Sat Apr 22, 2017 11:53 pm

Ok so I ran my a/c today in SoCal's first 90F+ day and it really didn't cool all that well unless I was roaring down the freeway. That led me to believe that the lack of a condenser fan causes poor cooling performance.

Ideally, I'd like to install dual low-profile fans in front of the condenser. I'd also like to hook up a switch by the HVAC controls that allows for: OFF/AUTO/ON. So I can power the fans off, leave it to only turn on when the compressor kicks on or turn it on. It also needs to be switched by the ignition so I don't have to turn it to OFF or AUTO every time I leave the vehicle.

The last electronics class I took was in 2003 in an Intro to Electronics class at the local city college. My knowledge of electronic diagrams and wiring is far below sub-par. I did, however, have a couple beers and drew up a diagram... which I sloppily drew on to Photoshop.

Can you guys see if this diagram makes any sense at all?

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1990 Isuzu Trooper 5MT - Pretty much stock all-around
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Re: Electric Gurus! - Gen 1 Condenser Fan Mod

Postby itsmehb » Sun Apr 23, 2017 7:53 am

Not totally following your diagram, but would like to add some input you may consider. Most cars with 2 fans usually operate with a single fan on and the second fan on along with the first fan when the a/c is turned on, or when a sensor in the cooling system senses a high temp condition. My 2000 Amigo had a single two speed fan. It normally didn't run at all when the a/c was off and the engine was operating at normal temp. If the sensor detected a high temp in the cooling system it turned on the low speed circuit. When the a/c was turned on the high speed circuit was energized and the fan ran on high. I do understand your on and off part of the diagram, just the auto part is confusing. I would make sure the fans do NOT draw more amps than the switches can handle. Normally a relay is in the circuit as 2 fans running can be a pretty large current draw.
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Re: Electric Gurus! - Gen 1 Condenser Fan Mod

Postby RickP » Sun Apr 23, 2017 9:14 am

That's not how I would do it. The way you have it, the fan load is going through the small gauge A/C compressor switch wire. Connect terminal 30 to a fused constant battery connection with large wire and fuse appropriate for the load of the fan. Use the same size wire to the fan from 87 terminal. Now connect power from A/C switch to 86 and ground 85. You can put a SPST switch either on 85 or 86. Now if you want the fans to come on without the A/C, you would have to add in another relay and use a SPDT switch instead of the SPST, which will supply 12v to 86 . You will also need a diode on the A/C switch wire to prevent back feed to the A/C clutch.

Let us know what fan you fit up there. I tried a couple small junkyard options with no luck.
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