2005 XC70 - Lukewarm heat - Next steps?

wczimmerman · Post by **wczimmerman** » 03 Feb 2023, 11:33

Might have members on more than one Volvo forum...this has been posted to one other site:

Ok, new member here but not new to Volvo's.

Question:

My XC70 had little to no heat in a recent cold spell here in the south. Did some reading and research and one of the common issues is a plugged heater core, however, I found a temporary trick of flushing the core to ensure flow. Well, I did that today and made sure Volvo coolant and distilled water was filled back into the heater core when complete. I saw excellent flow. Following that, we are getting more heat sporadically but if I turn on the A/C compressor, it goes cold even when one or both sides of the dual climate control are full heat. Without the compressor and with the recirculate on, we can get lukewarm at this point with occasional waves of warmer air here and there.

When I pulled back into the driveway, I turned the blower down to the lowest setting so things were quiet and I can hear a whirring back and forth at about the speed of wiper blades: "whir...whir.......whir...whir". So, I turned everything to full cold (no compressor) and I can hear a longer whirring and then silence. Turn it back to full heat and you get a long whir and then the whir...whir again. Seems like maybe a blend door motor may be having an issue?

I'd appreciate any thoughts on this. Given the dual controls, are there more than one servos for this? Should I be testing something else?

Thanks!

MDK · Post by **MDK** » 03 Feb 2023, 19:04

Yep, it's probably the blend door on the left (driver's side), it might sound like a woodpecker in your dash. The servo motor gears are plastic and they strip out. MDK

Post by **cn90** » 03 Feb 2023, 19:36

Usually aging heater core and thermostat.

I use Behr heater core and Wahler tstat.
Info in XC90 forum.

wczimmerman · Post by **wczimmerman** » 03 Feb 2023, 20:12

Interesting...would a blend door on the left side affect both? We're not getting consistent heat from any of the vents.

Thermostat I hadn't considered. Is there a thread with symptoms that I can match up to what I'm seeing?

Post by **vtl** » 04 Feb 2023, 09:59

wczimmerman wrote: ↑03 Feb 2023, 20:12 Interesting...would a blend door on the left side affect both?

No.

wczimmerman wrote: ↑03 Feb 2023, 20:12 Thermostat I hadn't considered. Is there a thread with symptoms that I can match up to what I'm seeing?

A factory thermostat in the 2005 car is long dead in 2023. They are good for maybe 10 years. I replaced one in MY05 XC70 in 2015, because it was bad.

Post by **chrism** » 05 Feb 2023, 06:13

If the temperature gauge is riding at midpoint then chances are that the thermostat is OK. If it’s below midpoint then the thermostat may be shot.

If you remove both the driver’s and passenger’s under dash panels and both console side panels you can see the blend door linkages and their drive motors on each side of the HVAC unit. Changing heat and AC settings should cause the linkages to move to their various positions without a bunch of clicking and clacking. You should be able to tell if the motors are turning without corresponding linkage movement.

While you’re looking at the driver’s side you can reach up and feel the heater core pipes to see if they feel hot or just like warm.

wczimmerman · Post by **wczimmerman** » 05 Feb 2023, 10:07

chrism wrote: ↑05 Feb 2023, 06:13 If the temperature gauge is riding at midpoint then chances are that the thermostat is OK. If it’s below midpoint then the thermostat may be shot.

If you remove both the driver’s and passenger’s under dash panels and both console side panels you can see the blend door linkages and their drive motors on each side of the HVAC unit. Changing heat and AC settings should cause the linkages to move to their various positions without a bunch of clicking and clacking. You should be able to tell if the motors are turning without corresponding linkage movement.

While you’re looking at the driver’s side you can reach up and feel the heater core pipes to see if they feel hot or just like warm.

It is running in the center for temp. The reverse flush of the heater core worked fine...plenty of flow. I don't hear any clacking or clanking and with the blower at the first setting I can hear the motors when I turn from full cold to full hot. The problem is that I never get full hot.

Post by **vtl** » 05 Feb 2023, 10:29

wczimmerman wrote: ↑05 Feb 2023, 10:07 It is running in the center for temp. The reverse flush of the heater core worked fine...plenty of flow. I don't hear any clacking or clanking and with the blower at the first setting I can hear the motors when I turn from full cold to full hot. The problem is that I never get full hot.

The gauge rests at the center in a wide range of coolant temperature. Volvo thinks the average driver is an idiot, so he/she shouldn't worry about details like more or less precise engine temperature. I forgot what temperature constitutes for the center "minimum", but it is far from what it really should. So your t-stat still can be stuck.

HVAC door actuators is possible to calibrate in VIDA. If that helped it means one of actuators is broken and in need of a replacement.

dikidera · Post by **dikidera** » 05 Feb 2023, 11:48

It could also be stuck flaps. I have an issue with my S60 where the flaps constantly move from open to closed(they redirect the airflow elsewhere) so it could be this as well.

Post by **cn90** » 05 Feb 2023, 13:35

The temp gauge is buffered so in the middle does not mean much.
Get a real thermometer and stick it inside the vent after a long drive and see what you get.
I posted info in forum, I don't remember off hand but it should be 160F.

Chances are your thermostat is bad, I'd replace the thermostat first.
Then address the heater core later.