Novas Forever

I bought a Taurus 2 speed cooling fan to use in my Chevy II and need help on how to wire it up. I want to use the PCM low and high speed fan requests but since there is 1 fan with 2 speeds how does it need to be wired up? Do both the low and high wires get power on high or does the low speed drop off when the high speed is called for? I understand that relays are used but anyone done this?

Dave_62

iTrader: (10)

The fan off the 3.8L Taurus works great for swaps. I have one on my Cutlass, and it can idle in traffic with the A/C on on a 100 degree day for a half hour and my coolant temp never exceeds 190.

Anyhow, as for your question, of the three wires coming off the fan, the black one is ground, and the orange striped is one speed and the yellow striped is the other speed. (I can't remember which is which) To find out which is which, touch the black wire to the negative terminal of a battery and one of the other wires to the positive. Then with the black still on the negative terminal of the battery, touch the other striped (only one at a time) to the positive. The speed difference will be apparent. I have the low speed relay hooked to the low speed side and the high speed relay hooked to the high side on my car like you are talking about and it works great. The low speed moves enough air that the PCM has never called for high speed yet.

Just to be clear, you can't wire this fan up exactly like the dual Camaro fans are wired, which is kind of a series connection to produce a low speed. The Taurus fan simply uses one relay for low speed and one for high speed, with only one speed powered at a time. This is important. If both speeds are powered at the same time, the fan will just fight itself and burn up. There is a low speed fan output from the PCM and a high speed output. Just wire each to the respective fan speed relay and you are set.

G-Body

iTrader: (4)

Dave, how do you have the relays hooked up so that both speeds are not actuated at the same time? The PCM is set up so that if you are in low speed it actuates the low speed relay, but in high speed it actuates Both relays. From what you said above it looks like if both speeds are turned on on those tarus fans it will burn them up.

Novas Forever

My concern was that the PCM would trip both relays when the high speed fan was called for and that would not be good. I think the fan will work really well if I hook it up correctly and be space efficient.

Dave_62

iTrader: (10)

Oh man, I hate when I get called out on being wrong....

G-body is right. When high speed is called for, both PCM outputs actuate all three relays in stock F-body form. I guess its a good thing my car has never called for high speed.....

You can still use low and high speed though. It would require a third relay. The ground wire of the low speed relay going through the N/C contact of the third relay, with the third relay being acutated in parallel with the high speed relay. That way, the low speed relay would release when the high speed is called for.

Or, if you don't want to go through all that trouble, you could just use one speed. Like I said above, the low speed keeps my LT1 Cutlass cool even in summer with the A/C on.

Guess I have a little rework to do on my daily driver.

Novas Forever

I appreciate you help on getting me straight on this! I had thought the same scenario with the 3 relays, one to shut down the low speed request. Then I also thought about just using 1 speed. It is nice to hear that someone else is on the same track as me

G-Body

iTrader: (4)

You don`t actually need a 3rd relay. Two relays are plenty. I was at school earlier and didn`t have time to make a diagram. But heres one now.

Dave_62

iTrader: (10)

That will work, but you have to be careful with the relay you use. On most Bosch type relays, the NC contacts are rated to carry only 20 amps, even on the high capacity 50 amp model. The Taurus fan pulls about 45 amps starting and 20-25 running.



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G-Body

iTrader: (4)

/\ How did you find that one out? I`ve only seen the one rating on the relay, is the NC contacts rating listed in a book somewhere or something? (Why does everything have to have small print?)

Hope I didn`t confuse anyone with my diagram above.

Dave_62

iTrader: (10)

I'll put this link below, hopefully the mods won't be offended....


http://order.waytekwire.com/IMAGES/M...og/219_059.PDF

G-Body

iTrader: (4)

Good info. I always thought that the NC and NO contacts would be rated the same, but obviously they are not. I wonder why bosch decided to make the contacts have 2 different ratings? Thanks for the link.