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My 2003 Odyssey EX AC and fan stopped working except when the fan speed was turned to max. After researching these forums I found that it was likely a bad blower motor transistor. I replaced the transistor tonight and now the AC and fan work when set to speeds other than max, but the fan will not shut off even when the climate system is turned to off.

The fan seems to operate at only the higher speeds, though it will adjust slightly as the temp control is moved up and down. The mixer valve seems to be working correctly and the air temp will change appropriately based on the set point. All this relates to the front fan. The rear units seems to be working correctly.

Any thoughts on why the fan only seems to run near max speed regardless of the setting, even when the system is turned off?
 

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Discussion Starter · #2 ·
Rereading my post, I see an important typo. What I meant to say is that the fan will NOT shut off, even when I turn the climate system off.
 

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Did you replace the "Transistor Assembly" in the passenger compartment? You mentioned a "blower transistor" and want to make sure it's the same thing. I'm referring to part number 79330-S84-A41. Various posts on here point to somewhat random issues with the Climate Control that seems to be resolved by replacing the Transistor Assembly.

However, I will add that I've never heard of a case where you cannot turn off the fan - one of the symptoms was the fan only working at its highest setting.

Good luck.
 

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Discussion Starter · #4 ·
Yes, I replaced the transistor assembly under the dash on the passenger side. The fan now operates on settings other than MAX but it does not seem to drop to low speed and it will not turn off.

The other symptom I'm seeing is that the A/C compressor only comes one when the temp control dial is at the lowest setting. When the A/C does kick in, the fan speed steps up. I'm not seeing anything abnormal when I run the self-diagnostic (holding "auto" and "mode" while starting the car).

I'm leaning towards the controller being bad since the system does not turn off, but I'm hoping that there is a cheaper explanation.
 

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Is the climate control set to FULL AUTO or just AUTO. In full auto, the fan speed switch has no effect.
 

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Discussion Starter · #6 ·
It doesn't matter if it is set to AUTO, FULL AUTO, or a manual setting; the fan runs at full speed all the time. Even if I switch the climate control system off the fan continues to run at full speed.

If I turn the temp control all the way down (60) then the A/C compressor will kick in, but that is the only way the A/C will run. Last night I verified that all of the fuses have good continuity and the relays seem to be working OK.

I read another post this afternoon with similar systems that leads me to believe that either I got a bad replacement transistor, not unheard of, or the control unit is bad.

When I check the DTCs on the climate control, the LCD alternates between 88 and the lower horizontal segment on the right hand eight. So far I have not been able to figure out what that means or if it helps me in any way.

Right now I am leaning towards the CCU being bad (that's what the service writer at my dealer thinks) but I don't want to drop that much money on a part unless I am sure that it will resolve the issue.
 

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Ask the dealer if they'd let you try another transistor assly. Repairing your old one is also an option iirc someone posted a link to a place that sells relatively cheap transistor(s) that over heat and burn out in the assly.
 

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Discussion Starter · #9 ·
I like the way you think, dvpatel! That is actually exactly why I dropped into the dealer today. Unfortunately they were not interested in helping, though they were more than willing to have one of their mechanics test it for me at their going rate. They were also very willing to sell me the parts with just one catch; no returns on electrical components.

There are other dealers though. I'll have to remember that next time I am in the market for a new car or some service.

Tomorrow I am going to try the light bulb test pjigar talks about in this thread: Climate Control Trouble - Won't Report DTCs

If that is inconclusive then I will repair the old transistor assembly and see what happens before going the CCU route.
 

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The new part should come with a 12 month 12K warranty. So, all you have to do is prove that the part's bad.

Also, be sure to check the plug(s) that go to the assly. Ensure that the plug is securely clicked in place and not lose.
 

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I still have the same issue. Rear blower refuses to turn off. replaced rear blower and transistor assembly; checked the relays and fuses, including the rear ac relay by the radiator. Blower operates correctly at all speeds but doesnt shut off unless diconnected at pass side (brown) connector under kick panel. I am stumped. Any hints?
 

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It has to be a stuck relay. Double check all the relays perhaps?
 

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Thanks for the quick response. I have available all the relays from a donor car. I will change them out. But is there a method to check the relays with a multimeter or other? Thanks!!
 

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Fixed the problem. It was a corroded relay hidden behind the C pillar on the rear passenger side. All is well. Thanks for the response!!
 
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