Mark 8 fan install

[JumboFriendly]

I just snagged a Mark 8 fan from eBay. I know I'll need a controller to make it work properly. I was thinking about trying to hook it up this way, please tell me if it's possible or necessary.

I'd like to use a switch on the dash to control whether the high or low speed is used. I figure during traffic or especially hot days, I can use the high setting, and use the low setting the rest of the time. This will keep the power consumption down, and allow the fan to not have to cycle as often. I'd also like to have another switch to allow the fan to run on low speed with the car turned off, to help with cooling between passes.

Again, let me know if it's possible or necessary, and what parts I'd need to make it happen. Thanks!

[gadget73]

a switch controlling a relay would take care of the high/low. The last one I wired that way used 2 relays to control it. One had 87a tied to the low speed, and 87 to the high. Pin 30 on the relay went to 87 on the second relay. The second relay simply turned power on and off. First relay switched the power between the high and low speed windings on the fan. I could actually draw you up a schematic if not for my lack of ability to make legible things in paint.

[JumboFriendly]

If someone has good paint ability and could help simplify this for me, you're welcome to give it a go. I can't quite picture it in my head. Maybe I could if I had the stuff in front of me.

Is it better to mount the relays closer to the fan, or switch, or does it matter?

[gadget73]

ok, since i cant sleep and can't find a pre-existing schematic that isn't either incorrect or unnecessarily complicated, here you go, hand drawn schematic goodness.

I'm using 40 amp bosch type relays, but it wouldn't be a bad idea to use something heavier duty, or you could simply wire a pair in parallel for increased current capacity. There should be appropriate fuses and such on the battery connections, but those are left out on the diagram here. Connections between the fan and relay, and from the relays to the battery should be of suitable guage wire, 10 ga should do the job.

For the diodes, basically any 1 amp or heavier diode is fine for the task, it carries nearly no current. If you don't have AC, then skip the second diode. I'm also assuming fan controller is one of those hayden type adjustables that normally operates a relay and not a fancy controller.

[JumboFriendly]

Thanks for the drawing. It helps, at least some. I'm not too familiar with automotive wiring, but I think I can get this figured out. This is the controller I was going to get unless someone pointed me towards a different one. I believe it was Overkill who said he used that one.

I'm not planning on running A/C. Please explain what a diode is/does. Doesn't it just keep the juice from flowing backwards, basically?

[85crownHPP]

i seen a hayden thermo-controller on amazon.com for 20 dolla

[P72Ford]

I just snagged a Mark 8 fan from eBay. I know I'll need a controller to make it work properly. I was thinking about trying to hook it up this way, please tell me if it's possible or necessary.

I'd like to use a switch on the dash to control whether the high or low speed is used. I figure during traffic or especially hot days, I can use the high setting, and use the low setting the rest of the time. This will keep the power consumption down, and allow the fan to not have to cycle as often. I'd also like to have another switch to allow the fan to run on low speed with the car turned off, to help with cooling between passes.

Again, let me know if it's possible or necessary, and what parts I'd need to make it happen. Thanks!

Rather than use multiple switches, I'd suggest one swtich with multiple positions. You know, one with off, and then two other postions. I've seen them in local auto parts stores. It will simplify the wiring and not clutter you interior with switches. Just my

[gadget73]

I'm not planning on running A/C. Please explain what a diode is/does. Doesn't it just keep the juice from flowing backwards, basically?

yes. one-way electrical valve. The reason its needed for this setup is to keep the AC from kicking on whenever the fan is automatically or manually triggered. The other one is to allow you to run the fan with the key off without powering the ignition circuit. Actually looking at it, I put one of the diodes in the wrong position. It needs to be between the fan controller and the relay, not between the manual switch and the relay.
Actually you could remove it entirely if you aren't planning to run your fan controller's power source from a key-switched source. I wouldn't necessarily suggest this as it would be possible for the fan to kick on randomly with the key off and kill the battery.

[JumboFriendly]

I want to use key-switched power, I think it'd be better and easier.

[85crownHPP]

Rather than use multiple switches, I'd suggest one swtich with multiple positions. You know, one with off, and then two other postions. I've seen them in local auto parts stores. It will simplify the wiring and not clutter you interior with switches. Just my

yes!

these are called single pole, double throw switches

[JumboFriendly]

But I likey switchy!

[85crownHPP]

more switches mean more wire, more mess, more headache. but by all means, if you like having many switches that much... go for it!
Though you do already have a switch that would let you run it with the engine off... the ignition switch!

[JumboFriendly]

If somebody wants to make up a purdy drawing like Gadget for one of those SPDT switches, I'd appreciate it. I can follow a diagram, and it's probably just a simple change, but I still need a little help. Also, how to hook up el switcho por favor.

[JumboFriendly]

I edited yours a little Gadget, to make it easier on myself when I print it out and try to follow it. I'll attach it. If I broked it, please let me know.

One more question... Would it hurt anything to put all the relays and wiring inside one of those plastic project boxes you can get from Radio Shack? I was thinking it would make it look better.

[gadget73]

looks fine to me.

no problem mounting the relays in a box, as long as they're reasonably secure so the wires wont break or anything you can put them in whatever you want really.