When i run A/C the brakes goto the floor?? Help!

[church1101]

Yeah... so when ever i turn on the AC and let it run a few minutes, the ABS light and the check brake light comes on, and my brakes go to the floor and barely stop me.... i need help. I have already had the ABS computer replaced and it did not fix the problem.

[NightRider88]

could possibly be a vacuum issue in the brake booster

[DAB77]

You need to have the ABS system scanned for codes.It's not going to be a vacuum problem. No vacuum= No assist=hard pedal.
do you have this problem if you don't use the A/C? when the pedal drops, it's usually a fluid problem. Have you done brake work lately that may have allowed air into the system? Are there fluid leaks? If not I would suspect a bypass in the master cylinder.

[MT-2500]

I would suspect a electrical connection or bad ground.
Check all battery cables and ends and connections and circuit breakers and fuses.
If the check lights come on check for codes and post back code no.
Is the charging system holding good voltage and amps when it does it?
Why was brake module/computer replaced?
MT

[Gabe25]

Originally Posted by church1101

Yeah... so when ever i turn on the AC and let it run a few minutes, the ABS light and the check brake light comes on, and my brakes go to the floor and barely stop me.... i need help. I have already had the ABS computer replaced and it did not fix the problem.

This really sounds like your master cylinder is failing or you have a fluid leak somewhere. Ensure that your master cylinder is full. Start her up, with your AC off. Step on the brakes, put her in drive, and release the parking brake. Now keep steady pressure on the brake pedal for about a minute, and see if the brake pedal goes down. If you feel it slowly going down, re-check to your master cylinder for proper fluid level. If fluid level has no change. Then I would say that your master cylinder is leaking, and should be replaced. If fluid levels are low. Check your front calibers, and rear wheel cylinder for fluid leaks. Post back your findings.

[old_master]

What "ABS computer" did you replace? If you replaced the hydraulic unit, the entire hydraulic system must be bled using an ABS capable scan tool. If you don't use the scan tool, it's impossible to bleed all of the air out and would explain the low pedal and the light coming on.