Wiring Mark VIII electric fan with rear heater switch

[wearsabrowncoat]

I am posting to request some direction on electric wiring.

Here is the situation, I am planning on replacing the stock fan with a Mark VIII electric fan. I have a variable speed controller (VSC) from flex-a-lite http://www.flex-a-lite.com/auto/31165-99943.pdf and Electric Fan Accessories at Flex-a-lite Consolidated The basic wiring is straight forward other than I am not sure what would be the best wire to tap for an ignition positive signal (#9 on wiring instructions).



The main help I need is with wiring a rear heater switch to serve the function of manual override on and off switches. Flex-a-lite offers illuminated rocker switches for this but I would prefer to relabel and wire up an extra rear heater switch to serve both functions. The flex-a-lite switches are single throw, single pole (SPST) switches and have 3 prongs as pictured in the above link. Pin 1 sends the signal to the controller when the switch is activated, pin 2 is ground, and pin 3 is a + 12V source.

There are numerous threads on wiring the rear heater switch:
https://forum.ih8mud.com/80-series-tech/148815-rear-heater-switch-pin-out.html
IH8MUD Forums - View Single Post - Dual Battery w/pic’s, verbose
https://forum.ih8mud.com/80-series-tech/247191-rear-heater-switch.html



Do I need to flip the LEDs contacts to account for the built in diodes or would it be easier to add a ground to the switch to get the green led to light up when it is manually 'on' and the orange led on when manually 'off'.

Wire by wire help would be appreciated. Right now my best guess is:

Open switch, desolder LEDs, turn LEDs around, resolder LEDs

Yellow - ground, will use the nearest ground point to the switch location within the dash
Black/White - power from cig lighter +
Blue/Black - to #5 on the flex-a-lite VSC to trip manual 'off' and light orange LED
Blue/Yellow - #6 on VSC to trip manual 'on' and light green LED
Green (not pictured in wiring diagram but should power/dim backlight) - tap 1 wire from cig backlight
White/Green (also not diagramed) - tap other wire from cig backlight

Ignition positive for VSC #9? I was thinking of using the alternator good signal again like on my dual battery solenoid but wonder if there is a limit on the number of relays the alt good signal will be able to drive.

Thank you in advance.

 

[sdog]

I have a Taurus fan wired similarly to what u want, I have a simple push-pull switch for my manual override, that being said, my override is only to shut the fan OFF for water crossings. It is run with 16 ga wire to a Napa golf cart 48v relay that is regulated by a Carquest thermostat. Everybody is usually partial to what they are familiar with, I like my setup. Don't really see why u need a double throw switch unless u want a manual on, off and variable switch. Seems like u could let it run variable all the time and then manual off when u need. One more thing - I strongly encourage you to install the module to allow the fan to run for a few minutes after shutting down, it makes a big difference in a hot clime. Cheers!

 

[nicholas]

So are you removing the engine driven fan and replacing it with an electric fan?

 

[wearsabrowncoat]

So are you removing the engine driven fan and replacing it with an electric fan?

Yes, I know there are a lot of people opposed to the idea but I plan on swapping it out prior to SC install. I have lots of reasons but mainly because there were times this winter that my truck never ever reached normal operating temperature (post temp gauge mod).

Sdog, I'm sure there are cheaper ways to wire it up but after doing the second battery via George's method I wanted an off the shelf option for this electrical wiring. Other than the manual override switches the VSC is pretty slick and does have a timed overrun feature after the engine is turned off.

The manual off is easy to explain for water crossing but also is a good idea if working around the engine and not wanting any surprises with the fan coming on.

The manual on will serve as a fail safe if the engine starts to runs hot and I suspect a relay or temp probe failure.

That being said, 99.9% of the time I plan on letting the variable controller do its job.

 

[wearsabrowncoat]

Also, my plan is to use the original shroud and not do anything that will prevent a complete reversal of this procedure if it is a horrible failure.

Sdog, did the Taurus fan fit the original shroud? I was looking at that option too but liked the cfm numbers from the MK VIII.

 

[wearsabrowncoat]

pics added

 

[wearsabrowncoat]

Update:

I bench tested the rear heater switch and it seemed to confirm my guess as to the wiring. I ended up opening the switch and reversing the two LEDs. Put it all back together and will move to the next step of the installation.

 

[lockd80]

Cool idea, I too rigged a heater fan switch to run my aux fan but never got around to getting the LEDs to work properly. Will be watching this build up for ideas.

BTW the supercharger will definately bring your rig up to temp faster.

 

[sandcruiser]

Can you explain some more about how you did the final wire-up?

Pics?

Thanks.

Update:

I bench tested the rear heater switch and it seemed to confirm my guess as to the wiring. I ended up opening the switch and reversing the two LEDs. Put it all back together and will move to the next step of the installation.

 

[wearsabrowncoat]

Can you explain some more about how you did the final wire-up?

I got sidetracked with some other projects but most of the wiring is in place. The exception being the temp probe but this forced me to use the override switch when I did a test hook up on my JDM aux fan. I pretty much followed the wiring as discussed in post #1. I did tap into the alt good signal again with no ill effects.

I have not yet installed the Mark VIII fan but I did find an example of how another person installed a Taurus fan in an Explorer: http://www.mysporttrac.com/MySportTrac/projects/EFanInstall.pdf
I was planning on using the same basic plan of trimming the Mark VIII shroud down and attaching it to my factory shroud. That way the procedure would be reversible if it was an electrical or cooling failure. And when I say electrical failure I am talking about drawing too much current to keep my battery charged and the fan and other electrical items running.

 

[rockdragster]

hey buddy I am in the process of trying to install the mark viii myself. the other night I tried to use the factory shroud to mount it to. There was not enough clearance after I did a fit test. I am now looking at making a custom shroud to off set the fan away from the front of the water pump.

I have a flex a lite thermosate that I am going to use and have a manual switch also to kill the power when needed.

 

[sandcruiser]

no worries on the wiring, I've got my stuff figured out.

 

[wearsabrowncoat]

hey buddy I am in the process of trying to install the mark viii myself. the other night I tried to use the factory shroud to mount it to. There was not enough clearance after I did a fit test. I am now looking at making a custom shroud to off set the fan away from the front of the water pump.

Was that after trimming the Mk VIII shroud?

If so I will have to work on a custom mount as well.

 

[rockdragster]

yes sir I trimmed all that I could. The mark viii is just so big. I have been looking a using the 2 top mount bolts along with some holes that are already bored along each side of the radiator to base off of.

 

[wearsabrowncoat]

Please post pics if you make it happen.

 

[rockdragster]

I temporarily used ty wraps

 

[rockdragster]

on the wiring I used an electric fan switch from advance. It has a temp switch for 185 I think ,not sure. Also a wire that goes to the A/c wire so that the fan comes on when ever the compressor is on I dont really like that part it blew a fuse the other day riding around in the snow with defrost on full blast. And also an ignition hot wire.

 

[wearsabrowncoat]

Thank you for the update. I see you had to make a whole new mounting system. Very interested in how it cools as it gets warmer. Please add an update this summer.

 

[Dissent]

Resurrecting an 8 year old thread! Did either of you guys end up getting the Mark VIII situated and how has it performed? How did it affect the Air Conditioner performance???