Mark VIII fan install

After finding out that the Mark VIII fan was too much for the SPAL V3 to handle, I decided to scrap the whole controller idea and make up my own harness/diagrams for a hopefully trouble free system. I designed it so that it operates much like an electric fan in newer cars. It also has a high speed manual override switch, as well as feedback through a single RGB LED for the various states (high/low/AC).

Mark VIII fan installed:




Wiring schematic & diagram:
http://www.motortopia.com/files/cars/album_mark_viii_electric_fan/49e13fa262ca5/FAN_SCHEMATICjpg_Thumbnail1.jpg

http://www.motortopia.com/files/cars/album_mark_viii_electric_fan/49e13f8ff3a8a/FAN_DIAGRAM_1jpg_Thumbnail1.jpg


Relays/custom harness wired up and ready to go:


(figured I may as well make use of the Maxi-fuse holder from a painless 70A wiring kit I decided not to use)

Headlight/fan relays mounted on bracket at battery tray:



I scratched my head finding a good place for the manual override switch and in my absolute refusal to poke holes in any factory panels, I came up with this:

...I'm going to mount the LED on the lower side of the switch, facing the driver. Unfortunately I couldn't find an LED bezel like I used for my alarm LED, so I'll have to figure out something there (may just glue the LED in place).

I just have to wire up things under the dash for the RGB LED and manual override switch and it should be good to go - I'll follow up with pics tomorrow if I get a chance.

Thanks guys - got everything finished up this morning... sort of...

Problem #1:
First thing I did was test the manual override switch - fan comes on, but both green and red are on in the LED. I unplugged the harness at the fan, and verified that only high speed was getting power. Turns out the high and low speed are not isolated from eachother within the motor, so anytime either speed is on, there is 12V at that terminal. Moving the red and green LED tap points to terminals 85 on their respective relays should solve that problem. Fairly easy fix since it can be done at the relays.

(This also means that the circuit could have been simpler as you can likely energize both high and low terminals and avoid having to interlock them like I did.)

Problem #2:
Fan only works with manual override. I have verified both low and high speeds work when grounding their respective trigger wires. This leaves me with a bad switch and adjustable t-stat, or more likely that the high temp switch needs to have the teflon tape removed (I never put it on, but this one came with it - should have taken it off) so it will ground properly, and I need to move the adjustable t-stat probe needs to be moved closer to the rad. I didn't want to mount the strap through the rad, so I mounted it to the fan shroud - easy fix with some spacers.

Here's a couple more pics of everything back together. LED looks odd because both red and green are lit up:


Relay rack fits nice and snug next to battery:

I tried what I wanted to do above for indicator lights and I wasn't thinking - putting the LED tap points at terminal 85 closes the relay as it will ground through the LED.

Got a chance tonight to verify all fan operation and all is well there. The GN switch turns on more like 220ish (which is fine for a high temp backup) and the Hayden controller isn't nearly as sensitive as it claims to be (claims lowest setpoint is 32'F - not a chance), but it does the trick at the temp I want. The A/C and manual high speed overrides work fine as well. I found the Hayden probe needs to be physically touching the rad, which makes more sense than how they recommend mounting it. I currently have it tucked up in the bracing at the top of the rad - it seems to work well there and it's out of sight, so I'll probably leave it. The flex-a-liate installation instructions for the same controller on summit's site state putting the probe through the rad like you normally would, but I don't want to destroy my fins as the probe just too big. The temp range stated for the flex-a-lite 31147 also seems more realistic at 160-240'F than 32-240'F stated on the Hayden instructions.

I've also designed another diagram to make the LED operate as I intended, but it involves adding a relay specifically for the control of the red/green LED's. I hate the idea of adding another relay, but it will be nice to have everything operate as per the original design and make use of the RGB LED.

Supe said:

Time to make this one a sticky.

Click to expand...

Don't go that far until I get it right! LOL That being said, I finally got the LED working the way I wanted it to. The design I mentioned above didn't work either - again because of the backfeed on the motor - it was causing one of the relays to latch/lock itself in and if low speed was on first, then it went to high speed, the LED wouldn't change. Fan operation was fine, but not the LED.

I was about to give up, but was able to redesign it yet one more time and finally have success on how I wanted it - using individual LED's would have been much simpler, but I really wanted one to do everything.

Only other thing I might change is right now I have high speed off of battery power - I may or may not leave it this way. The Hayden adjustable temp sensor doesn't have much of a spread between on and off temps causing the fan to kick on for 2-3 seconds every minute or so until it cools down. It should have more of a spread allowing it to run for a longer period only a few times. Simple fix if i want to put it off IGN power though.

I'll post the final diagram when I get a chance to pdf/jpg it at work, but for now here's the LED in the different stages:

Off:


Low Speed:


High Speed:


A/C:

Ok, here's the final schematic and wiring diagram:

Due to the unexpected operation of the Hayden controller with the engine off, I have made one final change to the diagram so that the fan will only run with the car on.

What was happening is the fans would run for a minute or two when the car turned off (as expected and designed for). I expected this might happen 2-3 times as the coolant would increase in temp again a few times once the fan stopped. This did happen, but the odd part was after a while the controller would call for the fan to be on for a split second every minute or so and this went on basically until the car naturally cooled down. This wasn't good for the battery and left me with just enough juice to crank the car over a couple times. I didn't like the idea of possibly getting stranded with a dead battery, so I made a minor change that only allows the fan to run with the ignition on:







On a side note, regarding how to tell the difference between the 1 and 2 speed Mark VIII fans, I put this quick image together for reference: