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Help! Our 2012 Odyssey EXL blows cold AC when moving but at stoplights or idling it's not nearly as cold. It has been this way for at least a couple of years, and only lately have I really tried researching and troubleshooting the problem. I've looked through the forums and seen many similar questions but have not found a solution. I've watched a few decent YouTube videos but still don't have a solution. I live in FL and it's in the upper 90s most of the time.

With the engine running and AC off, neither fan runs. With AC on, both fans run on low speed.

I've come to the conclusion that the fans never change from low to high speed, but can't figure out why.

There's a pretty good YT video that walks through a schematic of a 2012 Odyssey and shows how the fans and relays are supposed to work. Both fuses are good. I'm not sure how to test whether the PCM is calling for high speed. I tried a $11 fix and replaced the Fan control relay, which did not solve the problem.

Here's where it gets interesting. Hoping this sequence may help someone understand what it's doing and ultimately what's wrong.

1. With the engine up to normal operating temp and the AC on, both fans are running on low speed. It can sit for 20 or 30 minutes like that, and nothing changes. The fans never go to high speed, nor do they turn off.
2. As an experiment, I pulled F30, which is the fuse through which both fans get their power when they're running in series (low speed). As expected, both fans stopped running.
3. However, about 5-10 seconds later, the passenger side fan (radiator fan) turns on and runs on high speed.
4. I put F30 back in, and the driver's side fan (ac condenser fan) comes on, also on high speed.
5. Both fans run on high speed for about another 20-25 seconds, and then switch back to low speed. They stay in low speed until I try the experiment again, or I give up and turn the engine off.

This sequence tells me that the fans are able to run on high but for some reason they're not getting told to do so.
Step 3 above tells me that F29, the radiator fan relay, and the radiator fan are ok and working.
Step 4 tells me that F30, the AC Condenser Fan relay, the Fan Control relay and the AC Condenser fan are all ok and working.
Step 5 above tells me that something is commanding the fans back to low speed, and they stay there.

What am I missing? Do I have a bad PCM? How can I test it? What else can I try?
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What am I missing? Do I have a bad PCM? How can I test it? What else can I try?
An OBD-II scan tool...

What is the coolant temperature? (will need to remove any VCM defeating devices, if equipped) If the fans on low speed keep it below 195*F (I think, would have to double check in repair manual), then they will never turn on high.

It is very rare that the fans run on high speed.

I'm guessing/betting that you have low refrigerant levels and there is just insufficient refrigerant to work well at low engine RPM. Try revving the engine to ~2k in park/neutral and see if cooling improves. If so, it isn't the fans.

-Charlie
 
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