'05 Odyssey Front Heat blows cold, back heat blows warm...sort of :)

rodneydiller · Nov 3, 2012

Hello all. First time user. Thanks in advance for the assistance. A little setup: I have a 2005 Odyssey EX-L with front and rear heat. The rear heat can be controlled from the digital heater control unit in the dash, or you can control the heat with manual knobs on a control panel in the second row ceiling.

The front heater is not blowing warm at all, ice cold. The rear heater will blow cold if you set it to be controlled by the control unit in the dash. However, if I set the in dash control unit to rear control, I can dial the knobs in the back seat to blow hot.

I understand from reading some other posts that the van has 2 heater cores and the front heater core could need some repair. My thinking is, however, that if the in dash climate control unit doesn't make the rear heater work, but the rear heater will work when put on rear control, the problem lies with the in dash climate control unit. Does that makes sense? Is that the most likely culprit?

Disclosure: I'm not a mechanic, but can follow instructions and do some repairs. If I can't, I have friends who can

Thanks so much for your help!

DrD · Nov 3, 2012

ok - so the control panel for the climate control has a self diagnosis feature - to run it, do the following (from the Honda service manual)

1. turn the ignition switch ON(II)
2. on the climate control panel: Press and hold the <off> button. While holding the <off> button, press the rear window defogger button 5 times within 10 seconds. release the <off> button. All of the LEDs and LCD segments should blink 3 times, then the system enters the self-diagnostic.

If it finds a problem, it will light the "auto" indicator, and display some of the segments of the numbers in the LCD, then will alternate back to 88, then to the segments, etc. - each segment corresponds to a particular error condition (there are 14 of them)

turn the ignition switch off to stop the diagnostic. If you let me know which segments light up, I can tell you which errors they correspond to.

(as an aside - I am inclined to agree with you - since it can't even control the rear properly (but the rear control still works), I would guess there's an internal issue with the front panel)

rodneydiller · Nov 4, 2012

Great response! I'm into bedtime routine with the kids now, but I'll try this tomorrow afternoon after church and see what comes of it. Thank you so much!

rodneydiller · Nov 13, 2012

DrD: before I found this website, I had already bought a climate control unit off of ebay for $30. I installed it today and with fingers crossed, checked the heat. Same as before

. So, I did the system check like you described above. I'm not exactly sure what I am suppose to tell you from this reading, so I've attached two pictures to show you what is popping up. Does this tell you something? View attachment 13565 View attachment 13566

DrD · Nov 14, 2012

I get "invalid attachment" errors with both of your images - maybe put them on photobucket?

rodneydiller · Nov 14, 2012

Here the photobucket links are. I'm not sure this is telling me anything, but it didn't do this display the first time I ran it, but it did the second and third time. Let me know if this helps. Thank!

http://i1280.photobucket.com/albums/a487/rodneydiller/photo-1.jpg

http://i1280.photobucket.com/albums/a487/rodneydiller/photo-2.jpg

swaayze · Nov 14, 2012

There's a cable on a small lever arm just below the dash on the drivers side that directs the warm air (behind the kick panel next to your right foot) that came off of mine (the cable keeper broke). Slide the cable back over the arm and gently insert a small screw into the end of the arm to keep the cable from slipping off again. Voila, heat.

At least that was my easy fix, good luck.

DrD · Nov 15, 2012

Ok - so the display should be alternating between those two pictures - the first picture is the error code. It looks like it's the top segment on the first number (of the two 8's) - it indicates error code "C" - a problem in the blower motor circuit (which is weird, since your blower seems to be working - did you have the key all the way to on(II)?) - anyway, in the service manual, they say to check fuse 21 (40A) in the under hood fuse box, and fuse 30 in the drivers side under-dash fuse/relay box (it's probably not the under hood one since your blower works) the rest of the procedure is oriented at checking the wiring harness to the climate control unit and the power transistor - since your blower works, I am guessing the power transistor is just fine. If fuse 30 is out, then it would mess with the front control unit, but not the rear control panel, which could explain what's going on... if not, then some other things to check - when you have the front climate control on and change the temperature setting from very cold to very warm, can you hear the air mix motors running to adjust from cold to warm? Similarly, when you go from fresh air to recirculate, can you hear the recirculation motor move?

dadof5arrows · Nov 5, 2013

Ok, I have this problem exactly, and both fuses check good--so looks like perhaps the power transistor? Thanks for providing this thread, Rodneydiller and DrD!

GoHerdMan · Oct 25, 2020

i just checked and swapped out both fuses on mine and did self diagnosis mode and I assume it came back with nothing wrong because the light to the defroster stayed on and it did nothing more after 5 minutes of waiting. My problem is I do not have heat in the front or back all of a sudden

GoHerdMan · Nov 1, 2020

Fixed. Reverse flushed heater core and thermostat

'05 Odyssey Front Heat blows cold, back heat blows warm...sort of :)

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