A/C and Braking

[Nightsabre]

Just today I had experienced a strange situation in which I have the A/C on and I am stopped at an intersection. At approximately 2 second intervals I feel a vibration from the brake pedal and it can also be heard throughout the car. I am only applying partial, about 90% pressure on the pedal and the car is still slowly moving forward. Then I turn off the A/C and under the same amount of braking pressure the car stops and vibration subsides along with the noise. What would be the problem and how can it be solved? Please advise.

 

[Peewee]

One possibility is that your brake master cylinder is failing.

Hard to judge from a distance.

 

[Muzza_NZ]

are your engine revs surging at the same time?

 

[Nightsabre]

i don't really notice that, but next time it happens i'll keep an eye out for it. Also, it could be just my imagination, but to me it seems that i may be losing power as it looks like my "D" (drive) light in the dash is dimming whenever i hear and feel the vibration.

 

[UZZ30-Québec]

ABS freaking up???

one thing that suck a lot of juice to dim light is the ABS pump.

but it mustn't be that. Check your revs, mine does that sometime, the idle is long to get down when the A/C is on and the car wants to move. But i don,t have any vibration.

 

[Nick M]

Just today I had experienced a strange situation in which I have the A/C on and I am stopped at an intersection. At approximately 2 second intervals I feel a vibration from the brake pedal and it can also be heard throughout the car. I am only applying partial, about 90% pressure on the pedal and the car is still slowly moving forward. Then I turn off the A/C and under the same amount of braking pressure the car stops and vibration subsides along with the noise. What would be the problem and how can it be solved? Please advise.

Potentially it is more than one problem. The brakes being one, that you can not hold at 90%. The compressor is engaged, but the idle up function is not happening. Check your DTC's for a code 51.