Voltage drop when applying brakes

[js_og]

Hey people,

I currently have alternator issues, but something else is weird. At idle, voltage drops seriously when applying brakes. Is it only because of lights and alternator unable to provide constant voltage under load or something else?

Never seen that before...

[crazyrog17]

Could be a short in the circuit. Should pop the fuse if there is though.

[js_og]

I've read somewhere thatit could be caused by a vacuum leak from one of the PCV hoses?

[FestYboy]

when applying the brakes, there is a fresh air valve that opens on the back side of the diaphram (potential vaccum leak if the diaphram is perferated).

test your ALT this way: with a volt meter set on DC and the car running at idle, measure the voltage (should be more than 13.6vdc). now turn on EVERYTHING (wipers on low, all lights, blower motor, radio). re-measure the voltage (should be NO LESS than 13.4vdc). if the voltages are lower than either of the above, inspect the connections and after verifying all are good and clean (as they should be), replace the ALT.

on an alternate note: also test for AC voltage... you should see NO MORE than 0.5vac, if you do AND you know the battery to be in good condition, replace the ALT

the battery MUST be good and charged for all testing, a bad battery can give misleading results, especially with the AC voltage test.

[nitrofarm]

Hey people,

I currently have alternator issues, but something else is weird. At idle, voltage drops seriously when applying brakes. Is it only because of lights and alternator unable to provide constant voltage under load or something else?

Never seen that before...

I have a similar problem.I must admit I havent put a meter on it. But I can tell its an electrical load.(I also suspected my Brake booster) I had actually inquired here on the forumn,cuz its started after I "Opened up" my exhaust & removed the cat. Long story short,it appears to be the blower motor. Mine also idles low. Try unplgging the blower fuse.And see if it fixes.

[js_og]

well the alternator is blown up for sure, its bearings sound like a rolling bingo ball.
its at the garage for replacement now. I'll check all the above once it gets back.

Thanks fellas