Mark VIII fan wiring

jgfiveoh · Mar 20, 2007

getting ready to hook up my dccontrol to the mark VIII fan. question is what wires do i need to use on the fan harness. the black and blue are the power wires but is this low speed? what is the black and orange stripe wire and why does it split into two smaller wires and where do they go. is it a fusible link?

jgfiveoh · Mar 21, 2007

i guess i'm retarded or something. went to mercury today and looked at a book. the BR/O wire simply terminates somewhere in the harness. but why????

jrichker · Mar 22, 2007

They may use the same fan motor on serveral different vehicles with different requirements. The black/orange wire has a function (like low speed) that isn't used on the MK VIII.

jgfiveoh · Mar 25, 2007

i got the fan all wired up as per baskin's instructions and took it out for a spin last night. everything worked fine. i ended up wiring it to the brown and orange wire on the fan pigtail.

everything was going fine (temp right at 180) until tonight. when i went to start the car again my fan wasn't coming on no matter what i tried. i also have brians L101 LED light kit.

i had the underdrive jumper on (pins 13,14)

i have the temp sensor pins on correctly

the LED light is telling me that the fan is on full speed (green) but the fan is not moving or trying to move even. if i give it a little spin myself it wont even take off. it's doing this even after it's been sitting for four hours. the green light comes on when i turn on the ignition but no fan???

should i start by seeing if the fan motor is fried or check the fusible link in the FK35 kit?

but still it baffles me why the controller tries to ramp the fan up to full speed with the ignition switch on during a cold start!

i'm going to start by checking the fan tomorrow to see if it's fried. after all it's from a junkyard and who know what kind of condition the motor was in when i got it.

anyways i'm at wits end so please give some insight

HISSIN50 · Mar 25, 2007

Of course, it's best to contact Brian or check his FAQ (he has some voltage tests in there - it's where I'd start).

That said, I'll toss out a couple cents. Have you confirmed that you have power leaving the controller (enroute to the fan)? If you turn on the AC, does the fan come on? That would kind of indicate the fan is ok. ALso, you noted the fan tries to ramp up to full speed on cold start-ups. That indicates the fan works, no?

Though you've done it, I'd double check your probe again - they can be kinda finicky.

Also, on mine, the LED is red when the fan is on full speed. He might have changed things since mine came out though. My LED is yellow-green when the fan is not on (as when I start a cold engine).

I have not used the U/D jumper, so I can't comment about that aspect of things.

Good luck.

baskin · Mar 25, 2007

If the light is green, it’s indicating that the controller is off. The most likely problem is that the yellow ignition input isn’t getting 12V. It’s not critical without the U/D jumper, since the controller will over ride to on if it gets disconnected, but with the U/D, it will over ride to off so that it doesn’t kill the battery if the car isn’t running. The easy way to check it is to turn the AC on, it’ll over ride the ign input, but will only run the fan at 50% instead of 100%. If that’s the case, check your 12V connection to the ign and make sure that it’s good.

It sounds also that you have the regular continental fan (16” blade) If so, the or/brn is low speed, it’s not what’s causing the problem, but you’ll eventually want to change it to yel/brn (+) and blk (-)

jgfiveoh · Mar 25, 2007

thanks for chiming in brian. i've been extremely happy with the controller so far. there's just something a little funny going on right now.

i'm starting to think i have a mixed fan and harness. i'm sure the fan is an 18" mark 8 but i wonder if the pigtail is off something else. black(ground) blue (lo) br/or(high) i know because i checked them all to find the high speed set of wires.

i was starting to wonder if i was backwards on the light.

as far as the a/c goes i have none so i guess that's out of the question.

i wired the controller and light (ran separate power leads for each) about three inches off the ignition switch harness, which is also the where part of my Viper 791V alarm systems wired to (i just can't remember which part) is this a problem as far as amperage or voltage draw from the controller input?

i hope that gives an idea of what else might be happening but i'm still going to check the fan itself and check the connection of the ignition wires.

again thanks for the help:SNSign:

baskin · Mar 26, 2007

The AC input can be energized pretty easily, you can just use a small wire and connect it to the input of the controller. Also, are the inputs connected directly to the battery and how far is the controller from the battery? The fan is probably good, in the last five years, I've only seen two that were bad

jgfiveoh · Mar 26, 2007

yes the controller is wired directly to the battery. it is mounted between the battery and the driver's side fender with the leads less than eight inches long. there is no contact between the battery and the unit.

i can jump the a/c lead with the ignition lead or any 12 volt source and check for 50% power??

baskin · Mar 26, 2007

You can connect it to any 12V source, the high power input to the controller will work as well as the battery +

jgfiveoh · Apr 1, 2007

got the fan working, i guess there was a loose connection somewhere but everthings better now.

it does get a little warm cruising around. i think its cause of the not so great spot of where i had to mount the temp sensor for the dccontrol, which was about two or three fins away from the vertical edge of the rows but inline with the coolant outlet and out of the path of the fan and shroud.

just seems that the sensor is cooler than it should be. its pressed all the way in to the ridge.

180* therm

took it for a spin today (65-70*) car ran about 180-5 on the highway and sometimes 200 but no higher on the street.

like i said seems that the sensor isn't getting a good heat source...any suggestions on what to do with the sensor?

also no room to move farther inboard on the radiator without going behind shroud

HISSIN50 · Apr 2, 2007

You might want to just bring the car up to temp. Watch the mech temp gauge and the fan to see when the fan really spools up. When it really spools, note the temp reading.

Don't overlook the possibility that you might have an ancillary issue at hand (a lack of heat rejection for whatever reason - a bad t-stat, radiator that can't keep up at all times, etc).

Good luck.

baskin · Apr 2, 2007

The sensor placement should be fine. How fast is the fan running when the car is at 200? If it's not running full speed, there can be a couple of reasons for the high temperature. One possibility is that the radiator sensor doesn’t have a good thermal contact with the radiator or that that part of the radiator is quite a bit cooler than the coolant. If you need to, you can lower the set temperature 14 degrees with a jumper on pins 8/10

Another possibility is that the thermostat has some hysteresis, in other words, some thermostats open at a temperature that is quite a bit higher than what they’re specified for, but then close at the specified temperature, the higher quality thermostats with the bleed hole don’t do that. If the fan comes on late, but then ramps up very fast, that’s probably the case, the U/D jumper will stabilize it if you want to keep the thermostat that you have.

jgfiveoh · Apr 3, 2007

i have a mr gasket 180*(or milodon, all i rember is i got it from summit) balanced for high volume pumps. on the highway it stays real steady and won't go over 185 but its still possible and hard to know unless i pull it out and check the opening temp myself.

it just seems to have a little delay before it comes on. when it gets up to 200 it ramps to full speed for 20-30 seconds and then back down to 180-190ish.

i pulled the UD jumper off to see how it did, plus the fan was kind of squealing a little with it running 10%. is that just normal?

yes i was considering putting on the jumper to lower the operating temp and hopefully take out some of the delay in the system.

also,i think i speak for all of us here on :SNSign: when i say that we appreciate your dedication to your products and your customers

anyways i'm gonna play a little bit and see if i can get everything where i want it

thanks

baskin · Apr 3, 2007

If it settles to 185 and it’s consistent, then the install is correct, the thermostat is probably also fine. I haven’t been able to correlate why a few cars do this and what’s different on them while the rest don’t, they usually do it right after driving at speed under a light load. The lower cost thermostat will cause this and it’s obvious why, but the one that you have isn’t the problem, a lot of people use the same one and don’t have the over shoot.

The one thing that consistently fixes it though is the U/D jumper, it should completely eliminate the spike and only draws about 3 amps when the car’s sitting, on the freeway, the air flow through the radiator should spin the fan fast enough that the current will drop to about zero. The sound you hear with the U/D is the PWM frequency and it’s normal, but it should be far below the sound of the engine.

jgfiveoh · Apr 4, 2007

thats good news about the sound i was hearing and yes only when KOEO. i will try the UD jumper first, and then maybe the 8,10 jumper. i'll let you know how eveything goes.

Mark VIII fan wiring

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