low and high speed relays ties together, pic attached

[tta1401]

See attached pic. I have the relays tied together and it's been this way since I've owned it and never messed with it because it works. I'm going to be installing a dual fan set-up from alradco and I want to know why the green wire is tied into the green with white tracer wire? I've seen ways to bypass the low speed so it always turns on to high speed but the ties are different. Any clue on my set-up? I don't want to blow something.

 

[RmvBfrFlght]

Stock the low speed fan relay is ECM controlled. With the high speed fan relay coolant temperature switch controlled. Note that the A/C also controls both fans, but ignore this at this time.

The ECM controlled low speed turns on at a lower temperature then the coolant switch for the high speed.

By tying the two green wires together (DRK GRN & GRN/YEL), when the ECM turns on the low speed relay, it also turns on the high speed relay. This puts both speeds (or both fans on a dual setup), under ECM control to run at the same time.

RemoveBeforeFlight

 

[tta1401]

That's what I thought but wanted to make sure. Do you happen to know if the dual fan set-up will work the same or should I undo the tap?

 

[RmvBfrFlght]

The only down side to doing this with dual fans is the start up current surge. Dual fans usually move more air then the stock fan and also use more current. At idle turning both on at the same time can cause the engine to almost stall as the load hits the alternator.

Casper's has a relay set up that has a short delay on one of them to help prevent this.

RemoveBeforeFlight

 

[TurboDave]

I have one of those Caspers delay devices on my setup. We never could get it to work as designed because of my particular fan setup (no fault of Caspers). But what it does do is almost as good, both fans come on at the same time but the delay device on mine has them come on at a slower speed/lower demand, and then 8 seconds later they turn up to full on.

 

[H2Ogbodies]

Some dual fans are wired in series @ the fans vs. through relays so that could make a difference.

 

[tta1401]

Installed the dual fan kit from Alradco. I went ahead an left it jumpered and the fans worked as advertised. One fan kicks on then a few seconds later the second one kicked on. I'm leaving it and calling it good.