1936 LS1

iTrader: (10)

I've got a Cooling Components 2-speed fan. My harness is a modified 2005 Silverado harness and PCM. It is built with relays and plugs for two fans (like the truck had). How can I convert this to properly operate my 2-speed fan?

Been searching and reading on the forum and I just get more confused the longer I read! LOL

Richard

ls1nova71

iTrader: (4)

So you have 3 wires coming out of your fan, one labeled high, one labeled low and one ground, correct? In your truck harness, if the relays are already wired up, coming out of each relay will be a large power wire. Hook the wire coming out of the fan 1 relay to the CCfan wire labeled low, fan 2 relay wire to the CCfan wire labeled high, and the ground to ground.

74modified

Here is one I stole off of the web for a Taurus fan. Not sure your fan wiring.

74modified

I am pretty sure if you wire like this you are sending power to both high and low circuits at the same time. A two fan setup can have both running at the same time. To do this to a single motor ends up with a medium speed and probably not good for the motor

1936 LS1

iTrader: (10)

I contacted the harness builder and he sent me this diagram. Now I've just gotta figure out how to incorporate this into what I already have. I suck at this electrical stuff!

He called this a NO-NC relay (normally open - normally closed) any one know how to identify this relay so I can purchase one?

74modified

Look at the relays you already have. You need ones that have 5 contacts (connectors) on the bottom, not 4. They usually have a diagram on the side and numbers at the connectors.

74modified

If you have 5 contact relays, just move the wires around to match the diagram. If not pick up some good ones, (Bosch, Hella, Delphi), that will handle a lot of current. Then just add to what you have. I go to the U-pull-it and get them by the handful with wiring for very little.

a10beav

I did this a while ago converting a C5 dual fan to a Viper 2-speed single fan. Here's a link that helped me decided how to wire it: http://faq.dakota-truck.net/HOWTO/vi...n_install.html

These drawings should at least give you some ideas and part numbers for the relays. I drew up a simpler plan and used the wire for the single fan as my low speed switch and the wire for the second fan as the high speed switch. The drawings from the Dakota site gave me ideas how to connect those factory wires and new relays together to make it work. The set-up worked for years.

ls1nova71

iTrader: (4)

Really? I guess I'm not familiar enough with a 2 speed fan, I just thought they would have an internal resistor, and when the high kicked in, it would run on high by bypassing the resistor. How would it make it run at medium speed? Just curious, because if you have one wire putting out say 8 volts, and another putting out 12 volts, and you hook them to the same motor, wouldn't it get the full 12v?

busta9876

iTrader: (3)

This schematic will work fine, and will cut power to the LOW speed wire when HIGH speed is commanded. This happens when the HIGH speed relay is tripped. In the NON-ENERGIZED state, the HIGH SPEED relay passes 12v+ from the 30 leg to 87a leg, which then supplies power to the LOW speed relay on 87. This allows the PCM to command the LOW speed relay, and power the fan on LOW. When the HIGH speed relay trips, power is switched to the 87 leg, removing it from 87a. So, low speed relay no longer gets power on 87.

I have used a circuit that works too, might be a little less complicated. However this method works by removing the 12v+ to the low speed relay coil when high speed is activated, this could cause a DTC to set in the PCM for fan control circuit, so I usually disable the DTC when using this.

74modified

I did say that I didn’t know his particular fans wiring. It could be designed to have both circuits energized for high speed. Most two speed fans, like the Taurus fan, needs only one circuit energized at a time. They will work against each other and cause heat (premature wear) and likely be slower than the high speed circuit by itself. If you will notice, all of the posted diagrams feed only one circuit at a time.

ls1nova71

iTrader: (4)

I did notice that, and there must be a reason for it, but i just dont understand how the two could oppose each other, like i said, must be something inside the fan that i dont understand. The only thing i can think of, is they wouldnt want two wires hot at the same time, but even then i dont see what it would hurt. Im not saying you're wrong, all the schematics say it should be done the way you stated, i guess i just dont get it?

74modified

Well, I am not an expert, but I think most of these are brushless motors. A brushless motor has a permanent magnets on the inside of the rotor. Around the rotor are coils. The coils give out timed pulses to push the magnet, spinning the rotor. Inside is an electronic speed controller, which gives pulses of electricity at a certain speed to control the motor. The faster the coils pulse, the faster the motor will spin. When you have two pulses at different speeds they work against each other.

aknovaman

iTrader: (7)

How about we test that theory like this.

Connect an amp meter in series with the low speed power wire. Connect both high and low power feed wires to +12 volts and the single ground wire. I bet with the high speed fan operating there will be zero current through the low speed motor coils.

Better to measure it than keep on debating theory not based upon fact and measured data. Best not to guess, wonder or think, better to test and verify.

Just my opinion.

74modified

OK, let me know how your experiment works out. If there is current flow in the low speed circuit when both are energized, does that prove me correct? NO
If there is no flow under the same conditions are you correct? NO
It only proves that the fan you are testing works in that way. I have not given absolute answers in this thread, in previous posts I said I didn't know the circuitry of his fan and that some fans may run correctly with both legs hot. An aftermarket fan should come with instructions. Only an a$$ spouts off his opinion as fact when he doesn't know all the details. I said "may" and "could" because I have experience with this but not positive it would happen with his particular equipment. It was a warning from my experience of what could happen. I don't use aftermarket fans anymore; I find better value in OEM because of my experience with their cost & longevity.
What I do know is that I have actual first hand experience with using Taurus two speed fans.
A. Using a common feed for both circuits, It pulls more amperage with both speeds hot. A larger fuse is needed. More current = More heat=Shorter lifespan
B. When running on high speed, the RPM will drop once the low speed is connected. No, I didn't use a strobe light or touch the shaft with an analog tachometer, but it was very evident to my untrained eyes and ears.
C. Why have I not found a schematic for a two speed fan from a "knowledgeable" source that uses both circuits at the same time?
D. The OP was looking for a diagram. I gave him one that works. I gave opinion from actual experience, not something I read or heard about.
E. Just my opinion, and it is worth every penny you paid for it.

1936 LS1

iTrader: (10)

Update: never could get it to work the way my diagram showed it. Rewired it to the Taurus fan diagram that 74modified posted and it works great.