2 speeds with mk viii fan?

[my72vette454]

I have a mark 8 fan and it has 3 terminals on it but the middle terminal doesnt seem to be hooked to anything, how do I get both low and high speeds? Also where can I get a factory plug in for it, I have had problems with the terminals getting hot with those yellow female terminal ends snapped onto them. I have it on a forklift type loader and the fan needs to run all the time for the trans cooler but I think it has enough capacity that low speed might do the trick as if it runs on the thermostat it only stays on for maybe a minute then cycles off for a few.

Mike

[gmachinz]

Hmmm. The problem with a relay system (imo) is when it activates the fan, it sends full power to the fan-drawing a lot of juice. I've wired my car up both ways and I like using a progressive controller more. First, I like a constant temperature-I don't want the coolant constantly doing a balancing act, spiking up and down in temperature. Second, with a constant temperature, you get a steady rate of amperage use-which means not needing to feed it full power whenever it is on. It's easier on the fan motor and easier on the charging system that way. I see no more than 26 amps used to maintain my temperature of 150-160 now, (I removed a jumper on my controller because it was running a little too cool before). Before with just a HD 70 amp relay, the fan was seeing upwards of 56 continuous amps before it would shut off. Here's a little secret I learned also. I can't confirm this from companies like Powermaster, etc. but as for parts store alternators-even lifetime warranty ones, you get a cheapie version of the voltage regulator compared to a stock GM version of the same thing. The diff. is in the window time for a regulator to "recover" when it sees a sudden, high current draw. For example, in a GM 140-amp alternator you have a recover time of 6-7 seconds. In a parts store version of that same alternator, you will see about a 10-11 second recover time. Doesn't sound like a big deal until you go adding a ton of accessories. I was told GM is trying to reduce that time down to 2 or 3 seconds-it extends component life when it sees full power more quickly-quicker recovery time means a cooler running alternator and less voltage drop. Okay, so I ran off on a tangent but it sounds as if you're running too much power to the fan when it doesn't have to be running full power all the time. The rest of my blabbering is for those already running a Mark VIII fan on their car. -Jabin

[dhardison]

Jabin, What controller do you use?

Thanks,
Dan

[ponjohn]

I believe it can acheive two speeds only in the mark8, apparently there is method of doing this, possible with the climate control in the lincoln. Otherwise for our intentions it is one speed only.