no heat - winter is coming.

[gabejones]

Novice here.

Heater not producing hardly any heat.

The inlet/outlet coolant lines at the firewall are both hot to the touch, so the core should be seeing coolant flow.... the blower is good, all the actuators seem to work within the ventilation system.

Would a mostly clogged heater matrix still produce hot coolant on the outlet line? I am just not wanting to tear out the core and make a mess if there is some reason the airflow is going around the matrix somehow. Maybe I just need to flush the matrix and see what happens?

Thanks in advance

G

[cn90]

Use an infrared gun and measure temp at Tstat metal nipple (after a hot run), it should be around 85-90C. If not, Tstat maybe faulty.

Heater core: sometimes ppl mix diff coolant types, causing clog. Do you have service records?

How many miles in your car?

When posting problems looking for help, pls post year, model, engine, Auto/MT, odo reading and service records...

[abscate]

The P2 chassis always flows coolant through the core full flow , and temperature is regulated by mixing cold and warm air in the hvac system under the dash. It sounds like your blend doors have gone kaput try putting it into defrost mode and seeing if you get hot air to the windshield.

[gabejones]

Car has 195K on it, i have owned it since 135K and done no coolant flush. I don't suspect the blend door because I can see the control arm for the blend door move from stop to stop. (I can only see one blend door arm for one passenger side, the other is out of the way I cannot see it) I can detect heat when outside temp is on the warm side, when it is cold like below 40F then the air still is cool. The matrix is seeing some air. I guess the blend door could be partially stuck... but how do I get in there to fix the door. I will try the windshield and report back in

[cn90]

Get an infrared heat thermometer for $20.

After a hot run, turn the heat off so the heater core does not have to get rid of heat too much, measure the temp diff at firewall inlet vs outlet hoses and post it here.

If there is a big diff, then the HC is clogged.

PS: if you ever replace HC, stick to Behr, which is NLA, there are a few left on eBay...

[gabejones]

Get an infrared heat thermometer for $20.

After a hot run, turn the heat off so the heater core does not have to get rid of heat too much, measure the temp diff at firewall inlet vs outlet hoses and post it here.

If there is a big diff, then the HC is clogged.

PS: if you ever replace HC, stick to Behr, which is NLA, there are a few left on eBay...

Will do, I ordered it. Currently the hoses do have a difference to the touch after paying closer attention. One is hot, the other is hotter. It seems like I'm doomed with a partly clogged matrix, but will be fun to save $1000 doing it myself.

[cn90]

I wrote a heater core DIY in the XC90 forum.
All the tips/tricks are there.

[cn90]

I am posting this so everyone can see as a baseline measurement.

- 2005 XC90 2.5T with 132K miles.
- Brand-new thermostat and heater core (Behr).
- After a hot run (~ 30 miles).
- Car idling on driveway at ~ 700 rpm.
- Heat is off, cabin fan off.
- This is to simulate "natural heat loss" after heater core...
- So the Delta Heat Loss via HC is about 7 C under normal condition.
- Of course when you turn on the heat in the cabin (fan running), more heat will be extracted from the HC.

- Anyway, I am posting this here so ppl can use it to diagnose a bad HC. Under the same condition (same
ambient temp etc), a bad HC will show a bigger delta value.
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XC90-Heater-Core.jpg (152.67 KiB) Viewed 239 times

[cn90]

Anyway,

I went through this a few years ago with the 2005 XC90, after new HC, it is nice and hot.

[Antoine240bk]

Do the heater core while you can!
Mine blew up two days ago without warning and left me stranded far from my space & tools.
No choice to send the car to a Volvo shop. Looks like it is a hard work ahead said the Volvo tech...