Member Since: 11 Aug 2006
Location: Sydney
Posts: 64
No cabin heating
I'd like some pointers on diagnosing an issue with HVAC system blowing cold air and not heating. I've read through posts here, but what I've read doesn't seem to apply to my case..
Symptoms: No heating felt at all even with fully warmed up engine. Heat was barely felt at the beginning of this winter (I'm down-under in Sydney), and now cannot feel any warmth at all.
All vents are affected, including the rear outlets. I would have thought this would rule out a blocked heater matrix?
Setting the temperature dial to full warm makes no difference, nor does operating the rear system in independent mode, again full warm dial setting. I would have thought this rules out the temperature sensor issue.
I figure there must be a valve in the coolant loop that diverts the coolant into the HVAC system? If so, anyone able to tell me where it is located? Alternatively, while I have no coolant level warning, could the cabin system have become air-locked and may require bleeding?
Thanks in advance for any help.
2nd Jul 2015 3:20 pm
Narpy
Member Since: 18 Jul 2011
Location: Stockport
Posts: 7830
You're jumping to conclusions that may not be correct.
Read this, do a HEVAC reset and report back.
Narpy, I thought what I was doing was careful analysis using my existing general knowledge on HVAC systems followed by educated conjecture. I hadn't implied any firm conclusions..
Thanks for the link to HEVAC reset, and as I suspected, no errors reported - ie the ECON LED flashes a few times then goes off. When ignition is turned off then back on, no activity on Prog Defrost LED.
My diagnosis was based on the assumption that there are 3 heater matrices - one for each front seating positions, and one for the rear system. I figure it is highly unlikely all 3 would have blocked at the same time. It is just as unlikely their associated mixing dampers would be playing up all at the same time.
I also ruled out the sensor given that the rear system fails to heat up in independent/manual control mode, which should ignore the temp sensor.
In my book, that leaves heater matrices not getting hot water flowing through them. Any thoughts?
3rd Jul 2015 10:10 am
Robbie
Member Since: 05 Feb 2006
Location: ¯\_(ツ)_/¯
Posts: 17932
Well there isn't 3 heater matrices but check for heat at the bulkhead connectors. An IR gun is even better as you can trace the coolant circuit around and check for the temp drop between inlet and return.
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I hadn't implied any firm conclusions..
