When I filled this year, I got the compressor on for the cab a/c. Then I turned it off and the compressor would cycle. Had to fill more to bring the rear a/c back.

I think you can command the valve with forscan IIRC. Helps to have gauges so you know what is going on as you can overfill and lower cooling performance.

 

I'll post back next week around this time, should have the compressor valve in. A local AC shop in Carlsbad, CA agreed to discharge, install the valve and charge it up
I'm new to forscan and spending a bit of time trying to get more familiar, I did force the fans to run so it's helping
Thanks

 

Very pleased/surprised to hear you found a shop willing to do the valve.

 

Just picked up the MMH and AC in the cabin is very cold even at idle. The shop said that it wasn't low on refrigerant, but they did install a new control valve in the compressor.

Question, when the rear AC is working right, will the following happen on a hot day? can anyone confirm that this is the correct order for battery cooling.
1) the battery gets to a certain temp the blend door opens to let in outside air, and the fans start to run.
2) If the battery gets hotter, the blend door closes, cooling fans stay on, and the ICE will start in order to turn on the AC for the battery regardless of AC being on for the cabin.
3) evidence of the AC working properly would be a "cold to the touch" refrigerant line under the car back by the spare

Thanks, still trying to sort this all out
This is a 2009 so the compressor is ICE driven, not electronic.

 

Concerning #1 and 2, I believe it uses an ambient temperature reading to determine whether blend door is open or closed.
3) You can also see the rear evap temp in the BCM with Forscan.

 

Thanks S Keith. Maybe this is related, my MMH has 120,000 miles and the original MECS pump isn't sounding right, A new one is on order
Is it possible a bad pump might cause cause a chain reaction to eventually cause the battery to not function, so the AC might not get a signal to start cooling the battery pack?
Either way it won't hurt to have a new MECS pump cooling the electronics down properly.
Thanks

 

The new MECS pump body looks EXACTLY like the inverter coolant pump for the Prius. They perform exactly the same function - circulated dedicated coolant to cool the inverter.

I have seen MANY instances of intermittent Prius pump operation. Code + symptoms, but when checked the coolant is circulating. This happened on my son's Prius. We thought it was just a fluke until it came on as he was headed home. He turned around, came back, and prior to shutting down, we observed no flow. Pump replaced, No issues for about 2 years.

Given that experience, I would conclude the exact same situation is possible on FEH/MMH MECS systems.

Inverter overheating can often look like a grenade going off code-wise.

So many codes are interrelated, I always record the initial read, clear and see what returns.

 

I did install a new MECS pump last week and have tested it out on a few trips, so far so good
The old pump was original and it may have only worked intermittently, and when it did work the flow of coolant wasn't like what I'm observing now.
So perhaps it's as simple as a MECS causing all the cooling problems, we'll see.

 

I missed that you said "original." 120K has to be some kind of record.

Are you observing very low evap temps and battery temps < 90°F in the BCM?

 

Looking back I wish I swapped out the MECS pump right away (bought the MMH in Oct of 2021) but it tricked me into thinking it was working OK.
I haven't run forscan to see, honestly my skills with forscan are limited, I was able to run a fan test and did the battery rebalance many months ago but that's been it.