Cold weather causes brake failure???
 

The temperature hit 4 below this morning at Lake Tahoe. When I started my '05 FEH, the ABS and brake warning lights came on, along with a message to "check brake system." To make a long story short, apparantly the regenerative braking system was not working. The hybrid power display showed no green arrows flowing to the battery when brakes were applied, although I could stop. I drove about six miles with this condition, then parked in the sun. Three hours later, with the temperature in the mid 20's, I restarted the vehicle. All systems were normal. The power display showed a flow to the battery while braking. Has anyone else had this problem, and what is there about the braking system that could cause a temporary failure of regenerative braking in very cold weather? Thanks for your help.

Re: Cold weather causes brake failure???
 

Zero problems here. Going into second cold season, temperatures have dropped to as low as -40 degrees area.

Re: Cold weather causes brake failure???
 

I should have added that my vehicle was not garaged. It was outdoors all night in sub-zero temps.

Re: Cold weather causes brake failure???
 

Just some thoughts on possible causes of your problem.

I would not surprise me if Ford programmed the FEH not to use regen if the battery temp is below a certain temp. Charging is hard on very cold or very hot batteries. It may be to protect the reliability of the HV battery.

What is odd is the ABS warning light. I can't imagine that being a "normal" response to being parked outside in subzero weather. I would ask the dealer about it. Perhaps the brake system could be flushed to make sure there is no water in the brake lines?

Re: Cold weather causes brake failure???
 

We've had near zero off and on since October, and several weeks of consistently below zero weather here where the car is parked outside for 9 hours during the workday, and there have been no symptoms like that.

I've had one case where the car was very cold and the idle speed seemed to make "surges" to 2800 rpm every 10 seconds or so, and it felt that maybe it was being felt in the brake pedal.....but not much. It went away after about 5 minutes of driving. Other than that, completely normal operation. As expected, when the battery is cold there isn't much in the way of electric assist or charging until it warms up, but no lights and no odd symptoms.

Re: Cold weather causes brake failure???
 

My two cents is that the brakes lost its calibration. This happens when you disconect the 12V battery, or you have a computer glitch. The "check brake system" light would have stayed on till you did a reset by turning off the ignition switch for a few seconds and turning it back on. Since you continued to drive and not reset the system, the brake system remained in the protective mode.

Anytime you get a trouble light, you should try resetting things by a reboot of the computers. In addition, to recalibrate the brakes, leave the eCVT in "Park" and press the brake pedal all the way down till it stops travel. Let off and the computer will calibrate back to the original setting. If you still have a warning light, reboot by turning off the key and restart.

GaryG

Re: Cold weather causes brake failure???
 

I THINK the loss of regeneration is likely very normal at cold temps until the battery warms up. However that doesn't explain the ABS light and the check brake system..... That part might be something to have looked at. But even if they fix something I'll bet you still won't regen when its that cold at the start, I'll bet that is normal and not a symptom of the light and warning... The car will just brake like any other car in those conditions and still be safe.

Re: Cold weather causes brake failure???
 

No garage either :(

Re: Cold weather causes brake failure???
 

I tried that twice-- once shortly after I first started the ignition and again after driving a couple of miles.

The idea from others that charging is limited until the battery warms up makes sense. The ABS light is troubling, but I'm due for a 70k service, so I'll get the brake system flushed and checked.

Thanks to all here for the quick advice.

Re: Cold weather causes brake failure???
 

If the warning did not reset and came back on, your problem continued. You need to take it in ASAP so they can check for stored codes. It's more than a brake calibration or flushing the fluid I bet.

GaryG