Startup squeak

Hi Tom,

If you are adventurous and want to confirm that the coolant heat recovery pump is the source of the noise, then you can power up that pump at will.

To do this, make the car IG-OFF, then find the relay box mounted to the cowl. Open the box and look at the map of the relays on the underside of the lid. Find the CHRS relay and remove it.

Note that the relay has two copper-colored and two silver-colored terminals. Use an ohmmeter to determine which terminals are for the coil (they will show around 100 ohms resistance) and which are switched (they will show infinite resistance.)

Once you have identified the switched terminals, use a paper clip to short the relay socket terminals corresponding to the switched terminals. Then the pump will run and you can evaluate the pump sound vs. the squeak/moan that you have heard.

I suggest that you run the pump for only a few seconds at a time, since it is unclear what the rated duty cycle is.

 

I've had the same "moan" upon starting for quite some time. My wife laughs at the sound, always expecting it. I find, however, that it only moans when the air conditioner is "on"; not when the compressor is disengaged.
Recently I've noticed that it's been moaning, even after the one-time start-up moan. Almost like it's expelling flatus, for lack of a better description. Just little freeps about 10 seconds apart, not the longer start-up moan. I don't notice it when driving, but that may be a result of road noise drowning it out.
My guess is that it's a vacuum leak in the servo that regulates the airflow. If it gets worse, I'll anticipate that the Platinum extended service contract will cover it. If so, it will be the first item requiring dealer attention since I bought the car nearly 55,000 miles ago.

 

Follow-up question:
Does the Prius use vacuum assists, particularly for the controllers for the air diversion doors?
It just dawned on me that this start-up moan occurs without the ICE having started, so I now question my own diagnosis (vacuum leak).

 

There are three servomotors in the air conditioning system: air mix, air outlet, air inlet. These are electrically controlled by the A/C amplifier ECU.

 

My 2005 at 50k miles has the startup moan that I think is being discussed here. It appears to be caused by movement of baffels that redirect airflow between outside to recirculate and back. While I have only noticed the noise on startup, it can be recreated in IGN-on by manually switching between sources from the mfd.

I suspect that only those of us that normally operate with auto-AC-on have the noise. Sounds like a binding/scraping due to a mis-alined baffle or hinge in need of lubercant. I consider it a non-problem for now.

 

Your problem is the recirc/vent flap (or whatever). Its a common problem. When the A/C is turned on (or when the car is turned on with the A/C already on) the vents are switched to recircultate and that groan will occur. Later on, the A/C will automatically turn off recirc, so the next time you start the car, it turns recirc back on and you get the groan.

The groan only seems to happen when the car is hot (as in sitting in the sun for a couple of hours). When the car cools down, you can switch in and out of recirc with no groan. If you turn off the car and turn it back on a couple of minutes later, no groan. If you let it sit in the sun for a couple of hours and then turn it back on, then you get the groan.

I think you can test this by turning off the A/C, turning off the car, letting it sit in the sun and get nice and hot, then turn on the car. You won't hear the groan. Now just press the recirc button, but don't turn on the A/C. Now you will hear the groan. (Or at least some procedure like this can isolate it to the recirc function. I can't remember exactly how I did it.)

 

i would recommend listening to the chs water pump as it runs on its own, rather than powering it yourself.

if you're still in the 5/60 powertrain warranty, there's a tsb covering it.

 

I did this, and it groaned, just as you suggested it would, so I guess that flap is the source of the noise.

Although it's harmless, is this easily remedied by a do-it-yourselfer? If not, I have the platinum warranty, and I presume the repair would be covered. If I ever sell the car, the future owner may not be as amused by this groan.

 

Hey, do a search. There must be some kind of snake oil that will lube that thing up.

 

It is the a/c flap. I had the same problem and had it fixed. The door is binding and needs to be adjusted and lubed. Perfectly quiet now.

 

Since you didn't fill out your profile not knowing what year car you own
was it done under warranty? My 07 moans like a cow too when I chose between recirc and fresh.

 

i have a 2007 prius and had the ac/flap stuck open, how do u go about adjusting and lubing it? thx