Prius a/c evaporator leak

I measured the capacitors on my home AC units this spring, first time I ever had. They're years and years old.

The ones for the fans (smaller motors, smaller capacitor values) were still ok.

The ones for the compressors, not so much. They were both supposed to be 25 µF. One of them was down to 22.3 µF (more than 10% out of spec) and the other down to 20.3 µF (almost 20% out).

They're only about ten bucks to replace. The units were still starting ok, but start with less humming now, especially the one that was nearly 20% out of spec.

The new run capacitors I bought, of course, measured 25 µF pretty much on the nose.

 

^ I think I need to have that chat with my well pump. I think that's the only heavy motor in my home with enough age about it to matter.

 

Our house has a large inlet built into a cabinet with a grate at floor level and louvers on both sides. There is a duct that goes down from there under the floor and comes up through the bottom of the furnace. The base of the furnace has a rectangular filter, which because of the air flow direction, tends to get pushed up out of its frame, especially when dirty.

The grate was an odd size, so I put cardboard down around the edges so that now a 20x20 filter can sit on top of it. That is held down by some half bricks (which were sitting unused in the backyard). This first filter catches dust much better than the one in the furnace ever did. There is still a filter in the furnace, but it never gets dirty because the first one works so well.

The outside unit is cleaned regularly, but getting to the evaporator in the house to clean it is pretty much impossible. It is mounted above the furnace in the same air path, inside a sheet metal case, which is in turn wrapped with fiberglass. There is no way to see it, let alone clean it. I recently bought a boroscope for a plumbing project. Perhaps now I could snake that up through the furnace burners to at least inspect the evaporator.

 

Wow that sounds very difficult to get too. How were you supposed to clean the evap coil?

 

Yes good idea to check. I have a Sencore LC102. Don't use it much anymore but still nice to have.

Its a good idea to keep a start up cap and a contactor in stock those routinely fail over the years. Cap is cheap. Like you the second I hear any shenanigans when the compressor starts up I throw a new cap in there. Works well never lost a compressor on any ac unit I have ever owned. Keep the keep the condenser coils really clean keep the sun off the condenser unit and it should last for years.

 

That would make it easy, but the price of that instrument would keep me at bay, for as often as I'd really use it, unless I stumbled on one at university salvage or something.

My Fluke multimeter has a capacitance function that is able to measure the small ones for the condenser fans, but for anything around the 25 µF size of the run cap, it just says big.

So I ended up just taking the cap out and feeding a sine wave into it from a function generator, and watching the RMS voltage and current, and dialing the frequency f to where the current was exactly 1/100 of the voltage. Then I just plugged that into 100 = 1/(2πfC) to find C. (The choice of 100 was arbitrary; just easy to see when the voltmeter and ammeter were on the same number except for the decimal point.) So if that happened at 78.5 Hz, then the cap was around 20.3 µF.

Easier for me as I don't have that kind of specialized instrument, but I can make sine waves and measure volts and amps.

 

Well, the first part anyway. As far as I can tell the only downside to having the condenser unit in direct sun is the extra heat applied to the electrolytic capacitor. That type of capacitor tends to fail from having dried out, and the hotter it is, the faster that will happen. As far as operating efficiency goes, clearly the unit should not be surrounded by a sun heated asphalt surface, since then the air going into it will be at a higher temperature. Ours happens to be mostly in the shade, but more importantly, it draws its air from above a shady lawn.

 

Prius 2 evaporator leak is pretty common after 10y/200k miles or more. Especially if we live in hot climate. The leaks are from the aluminum welding and joins. No sealer will works because it is nothing to do with the rubber parts. I opened and replaced mine in 2017. It was a big job, literally 15 hours or more. We need to have dedicated hose and gauge (not mixed with other cars that user PAG oil)., 2 cans of 134a, coolant SLLC, vacuum pump, some hex sockets and screw drivers. We must access the HVAC unit which is combination of heater core, vents, and evaporator lines. We should buy a ND11 oil also to lubricate the new rubber seals on all joints.
It is indeer expensive job, $1500 because the steering wheel need to be moved around, the whole dashboard is out together with metal bars in a pillar. Fortunately all the 100 connectors have different shape and we will not mix them.

 

Nice job John you are 100% correct in everything you said.

I went through it at 12 years in on my bought new 2007 G2. It took the ac shop about 10 days to do it I went to the shop to see how it was going and everything I mean everything is removed right down to the firewall in the interior. Crazy! Looks like a hundred connectors dangling. OMG.

The owner said its pretty common to lose the e-coil on a G2. I can't remember exactly what the bill was but it was around $1500.

 

I’ve seen really good technicians who’ve done seven or eight Prius Evaporators take 4 1/2 hours. But that’s moving their nice person no brakes and they’re good..

Most take around book time is 7 1/2 hours.

I have seen a beginning technician with about 2 1/2 years experience, but he’s never taken a dash apart in his life.
It took him 22 hours his first Prius. He’s a little slow but he was successful and got the job done.. he’ll be faster next time.

 

This vehicle had multiple leaks over a period of time other ones were easy to find out under the hood like the condenser.

But this evaporator just did not want to leak under normal static conditions well in the shop. And if it wasn’t for that dog hair and all the dust, because they ran the AC without a cabin air filter.. all the dust in dog hair, absorbed the leaking oil and UV dye

So the UV die in oil never dripped to the bottom of the pan and rolled out the water drain tube where I would be able to see it with a UV light. Don’t run your Prius without a cabin air filter. !