Blis on 2017 C-Max

[ShoDog]

I have a 2017 C-Max.  Bought it new.  It has Blis.  I live in Iowa.

When it is below 32 degrees F and I put the fan at max speed, the left mirror Blis light goes on.

When I lower the speed manually to less than 60%, the light will go out and everything is just fine.

I never have this problem at temps over 32F.

 

Dealer verified the problem, but cannot find a cure. 

Switched mirrors, same problem.

Switched rear sensor, same problem.

Replace left door control module, same problem.

Replace the main control module, same problem.

 

I am giving up now since I think there is no solution for it.

 

Personally I think the blower motor is giving of a electrical noise that effects only the left side and turns on the mirror light.

 

Even in the cold, it works great except when fan in at max or near max speed and temp is below 32F.

 

Anyone have this same problem?

 

Thanks,

 

George

[joshg678]

That’s hilarious. I don’t have a 17 but I think your Right

[plus 3 golfer]

Try this as a possibility. Could the wiring to the mirror be faulty? or was it checked to be OK?

 

My guess is that around 32 F the BCM broadcasts the message to heat the mirrors. So, voltage would be applied to the mirror heaters by the door modules. The messages to the door modules are sent over the CAN. So, it likely that the heater messages broadcast over the CAN are causing the light to come on at freezing temps somehow.

 

I have no idea whether the algorithms might do the following but somehow the light is coming on. Perhaps the heater control algorithm adjusts the voltage to the heaters based on other data and reduces voltage once the mirrors reach the defrosted state, as it would take less power to keep mirrors warm. The BCM might broadcast messages to reduce the power to heating elements based on other data. Perhaps blower speed might be used as a proxy for level of frost on mirrors (one usually cuts blower speed when windshield begins to defrost). Maybe the wiring / connectors to the heater from the door module has a path to the light wiring such that the light comes on when full voltage is applied but when voltage drops the light goes out.

Edited February 8, 2019 by Plus 3 Golfer

[ShoDog]

Try this as a possibility. Could the wiring to the mirror be faulty? or was it checked to be OK?

 

My guess is that around 32 F the BCM broadcasts the message to heat the mirrors. So, voltage would be applied to the mirror heaters by the door modules. The messages to the door modules are sent over the CAN. So, it likely that the heater messages broadcast over the CAN are causing the light to come on at freezing temps somehow.

 

I have no idea whether the algorithms might do the following but somehow the light is coming on. Perhaps the heater control algorithm adjusts the voltage to the heaters based on other data and reduces voltage once the mirrors reach the defrosted state, as it would take less power to keep mirrors warm. The BCM might broadcast messages to reduce the power to heating elements based on other data. Perhaps blower speed might be used as a proxy for level of frost on mirrors (one usually cuts blower speed when windshield begins to defrost). Maybe the wiring / connectors to the heater from the door module has a path to the light wiring such that the light comes on when full voltage is applied but when voltage drops the light goes out.

 

I doubt that the wiring to mirror is at fault since all works well above freezing temps.  I do not have the defroster on when I put the fan at Max speed and the Blis light goes on.  Mirror defrost is off.  One interesting fact is this winter the temperature needs to be below 5F and is comes on very rarely.  Something is better this year than last year.  I am still thinking it is the fan itself and as it gets more wear on it, it changed its noise output signal for the better.    I did notice that the C-Max for Europe has a noise capacitor across the fan motor. The US version does not.  Same wiring diagram except it states that the capacitor is for Europe only.  I should buy that capacitor and put it across the fan motor, for that may be solve the issue.  I told the dealer's mechanic this when they were trying to find the cause last year.  Never heard back.   Oh well, I am getting used to it and think that I will never find the rear cause of the problem.  I still have one more winter of warranty on the car, so if it changes for the worst, I can then bring it in.  The dealer has an open case on this problem with no resolution.

Thanks for the input and have a nice day.

[WanderingSingers]

Same type of odd BLIS blinking in left mirror.  Soooo valuable when it is working correctly.  

 

Living in the NW, this happens with my 2017 when it rains and when trees are on the other side of the road....Hmm - think maybe it blinks all the time?  Yes. 

Wintering in AZ - no extraneous blinking for months.

 

Have been in the shop 3 times, complained noisily to no avail.  Last time they took a day to look thru more thoroughly.  Telling me that it is all controlled through wireless signals not wires.  Not sure that is true.  Don't know how to get a complaint to FORD or is this a safety issue?  Since it always blinks when it needs to and many times when it doesn't, probably not a safety issue.  Dealer says complaints to FORD will only have FORD send us to another dealer.  He also said the module is in the taillight....losing faith.