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Discussion Starter #1 (Edited)
My wife recently reported the AC staying warm when starting the van and not getting cold soon, like our 2003 Ody. The best I could get today checking from the center vent was 62.4F.

I have run the self check and got DTC B1221 for open in the rear mode control motor circuit, but my understanding is that won't affect cooling, only whether the air blows out from the top or bottom in the rear.

As @John Clark mentioned, I checked the cooling fans. I warmed the van to operating temp with the AC off and even after reaching mid-temps, it took a while for the fans to turn on, but they did and remained on. Then I turned on the AC. It took another 5 minutes or so for one (or both) to kick into high speed. I couldn't tell if it was one or both, but they were both still turning.

Pressures:
  • Static pressures (van off) - 105 and 120 (I had just run it a little earlier)
  • Starting with a medium-warm engine, 97 degrees at passenger foot level, while idling at roughly 700 RPM:
  • Front AC on (rear off) - 35 and 225 -- both fans turning at low speed
    • My understanding is at 221 psi, the AC pressure switch should have changed the speed of the fans to high.
  • Front and rear AC on - 50 and 310 - both fans still at low speed (1540L)
    • It took 2 more minutes for the fan(s) to go to high speed, which dropped the pressures to 40 and 225
1. Should I check pressures at idle or some other RPM?
2. Should I check pressures with front AC only or front and rear?
3. What other advice do you have? I'm about to go check all the relays and fuses I can find but would appreciate y'all's collective expertise in troubleshooting.

Thank you!
 

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Most likely a low refrigerant charge. Pressure gauges won’t tell you much as Proper charge is based on mass not pressure.
Bad AC clutch relay is very common.
 

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Before you start messing with refrigerant levels, lets go back to the fans.

Any time the engine is running and the AC compressor is on, BOTH fans should be running on low speed, even with a cold engine. Do you get both fans running on low speed? If one fan is bad, neither fan will run on low speed since they run in series on low. Once the pressure in the AC system reaches 221psi, BOTH fans will run on HIGH speed.
 

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Discussion Starter #4
On that prior test, I kept the AC off until the fans started running on low speed, then turned on the AC.

This time, starting with a cold engine, both fans ran at low speed every time I turned on the AC. When I turned off the AC, they stopped. With front and rear AC on, pressures went to 50 and 250 and neither fan went to high speed.
 

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So that confirms just a high speed fan issue. I wanted to make sure the fans ran on low when commanded by the AC not just the coolant temp. Everything else looks normal. When you turn on both AC systems you are pulling more heat out of the cabin and that will cause both pressures to rise. If the fans don't kick on to high speed then the heat can't be removed from the condenser to lower the pressure (and temp) on the low side

There is a TSB for no high speed fan operation on the 07 Ody. This might just be that issue. See below:


It could also be the pressure switch not closing above 221psi. The pressure switch is back on the right rear side of the engine compartment. It's a 4 pin sensor. When the pressure reaches 221psi the switch between the brown/white wire and the black wire closes, pulling the brown/white wire to ground.

That's where I'd start.
 

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Discussion Starter #6
Since the TSB is for a software update (non-DIY), I'll start by checking out the pressure switch. Thank you!
 

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Discussion Starter #7
I emailed Gunn Honda on Monday to ask about updating the software and got no reply. Then I chatted online Wed and they said they'd call back. Nope. I called Friday and left a voicemail, with no reply. I called this morning (Saturday) and they said it's $75 for the diagnosis only. If I just go in and tell them to update the PCM (a 12-minute software update), it's 1 minimum of 1 hour of labor, at $148.

Do y'all know if Honda (central) can pull up the service history to see if the PCM is already updated? Gunn Honda claims they can't see any service history.

Time for me to go check that pressure switch to confirm it's good or diagnose it as bad... then when I'm hot, tired and frustrated, a $148 software update will sound good.
 

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Have to check with a scan tool.
 

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Discussion Starter #9 (Edited)
Should I think of the PCM software like an operating system on a computer? In other words, one OS for the PCM, rather than separate programs for separate systems? So if I get the PCM updated, it would go to the latest version?

EDIT: I'm asking because I had TSB 09-053 performed and it says to update the PCM A/T software to 37806-RGM-A87. TSB 07-051, for the A/C fans, was released earlier and says to update the PGM-FI to 37805-RGM-A84.

If these are like individual programs, then the auto transmission fix wouldn't do much for my A/C and radiator fan speed, BUT if it's like a singular OS, then I should already be updated.
 

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Discussion Starter #10
Final update: PCM software has different modules, so the update for the transmission (on the A/T module) wouldn't affect the A/C, which is on the PGM-FI module.

Based on @John Clark wisdom, in this and many prior posts related to similar issues, I wrung out the entire system verifying all the individual components seemed to work, until the only thing left was the TSB for the fans not going to high speed at 221 psi.

I called a few dealers this morning and most just quoted a price for diagnosis or 1 hour of labor for the update. But Mando at Northside Honda asked the VIN. Then he took the time to look up my van in the system and told me I needed a PCM update for the A/T judder (which I supposedly had already done in 2009) and it would be free, as part of a campaign. His personal attention at taking just a few more minutes to look that up won me over. So I got the A/T update and they performed TSB 07-051 also ($116). They warned it might not fix the issue, but I had them update the PCM anyway.

When I got home I let the engine cool, then tested out the A/C. I was nervous. If it failed, I would go back to banging my head against the wall. Success! Both fans kicked on right at 221 psi. Thanks for another good fix, OdyClub!
 
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Glad to hear that. Your ability to follow instructions and post back clear concise details of what you had done and the results of your tests made it easy to guide you to the PCM being the issue. It was clear to me your PCM was the issue whether due to the need for the TSB or just a faulty PCM.

What's unclear to me is what actually changes in the PCM for it to go from an ability to command the fans to high but then suddenly stop being able to do that, requiring a simple (relatively speaking) software update to fix.

Thanks for posting back the eventual solution.
 
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