Weird brake pedal feeling with AC on

Hank3

Asian Persuasion <><
Contributor
:
2010 Mazda5 GT
Was hoping someone could help me identify/troubleshoot an issue I'm having with my brake pedal. At stoplights while idling; AC is on; and foot on brake pedal...I can't tell if it's when the AC cycles on or off but the brake pedal will go down a little further by maybe a 1/4 of an inch. It just started happening and I haven't messed with the brakes or AC recently.

Logically my head is thinking that these two things (brake pedal and AC) are independent of one another so it's weird that I'm feeling the brake pedal depress a little further. It only occurs when the AC is on.

Any ideas?
 
? Change in engine vacuum with increased load from the compressor? [shrug]

As long as it is only with ac (and not sinking to the floor) you should be good..
 
? Change in engine vacuum with increased load from the compressor? [shrug]

As long as it is only with ac (and not sinking to the floor) you should be good..


This, only way the two systems are interrelated other than being bolted to the same car. You MAY want to troubleshoot your vacuum brake booster (check to see if the diaphragm is on it's way out, holding vacuum, ect.) and make sure the vacuum hose is in good repair, but otherwise I think you're fine. Worst case scenario you lose your brake booster, you get a Hell of a leg press workout smashing that brake pedal without the power assist.
 
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