Strange air conditioning power sap

[Elan_]

When I have the AC turned on I experience some kind of power sap for about 5 seconds every 30 seconds. It feels like when you're driving at highway speeds and hit a sudden head wind. I'll be on level ground, consistent accelerator position and I'll lose a bit of power suddenly. I'll drop 3-4 MPH over 5 seconds and then it'll go away and I'll speed back up. This happens about every 20 or 30 seconds. This doesn't happen if the AC is not turned on.

I have no idea where to even start looking.

 

[EdmundGTP]

Well... Being that it only happens when the AC is on should give you a good idea where to start.. The power dip you're feeling is the AC compressor clutch engaging to spin the compressor.

 

[blackoutt]

Lots of us have complained about this. Some have found it was caused by pressure switches in the system telling the clutch to engage/disengage all the time, others have found a bad or dirty thermistor under the dash that caused it. I never got to the bottom of mine but have learned to live with it.

 

[RPC]

When I have the AC turned on I experience some kind of power sap for about 5 seconds every 30 seconds. It feels like when you're driving at highway speeds and hit a sudden head wind. I'll be on level ground, consistent accelerator position and I'll lose a bit of power suddenly. I'll drop 3-4 MPH over 5 seconds and then it'll go away and I'll speed back up. This happens about every 20 or 30 seconds. This doesn't happen if the AC is not turned on.

I have no idea where to even start looking.

My 2008 V8 SR5 has done this since day one.

 

[Elan_]

My 2008 V8 SR5 has done this since day one.

Since day one from the factory or day one second hand?

 

[RPC]

Since day one from the factory or day one second hand?

I bought it new Feb of 2009. Since I rolled it off the lot the AC has sapped power when the compressor cycles on. Exactly how you described it- at freeway speeds it feels like you hit a headwind. Also noticeable when sitting at a light with the AC on- when the compressor cycles on it'll lunge/surge forward. It isn't propelled forward violently or anything, but if I have just enough pressure on the brake pedal to keep it stopped and that compressor comes on, it'll jump forward.

I posted something about it a long time ago, I'm sure you could find it in my history (probably about seven years ago if I had to guess). I took it back to the dealer several times, went on drives with Master Mechanics who also felt/acknowledged it, but ultimately said it was "operating as designed".

Though it's irritating, I didn't think it was dangerous but I worried it would degrade into something more. I told them that if they couldn't fix it, to expect to take the vehicle back under CA's Lemon Law and that's when the Toyota Regional Service Rep got involved. He offered a 7yr/100,000mi Toyota Platinum Warranty to cover any eventualities. I thought that was fair and accepted.

Like I said, it has done it since day one, has never gotten any better or worse and if I drive it today with the AC on it'll feel exactly like it did when I first drove the vehicle 7+ years ago.

 

[Elan_]

Well I feel a little bit better about it then. It surprises me Toyota wouldn't recall such a regular and noticeable problem like that.

 

[JB.]

2005 bought new has done this since day one with no change or deterioration.

Often this kind of stuff is as much or more a variation in perception and description as it is variation between vehicles.