Heater is not blowing very strong.

[scot850]

If the coolant temp is registering low, it may be the thermostat failing or the ETC failing or both.

Having said that, the engine should eventually get up to temp and then you should get the full heat.

Otherwise it could be the cabin temp sensor that is clogged/failing or the heater fan.

Neil.

[Ailanthus]

Where is the cabin temp sensor? I'm having a similar problem except the temp gauge reads normally. I was thinking of trying to backflush the heater core in my case, but the temp sensor may be an easier check.

[nsjames]

have you checked the coolant level?

[MarcM]

Temp sensor is behind the little 3-slot grille between defrost/face/floor buttons and passenger temp control. Some people say to vacuum it, but you risk the chance of breaking the thermistor. I took the whole center console right out trying to diagnose a similar issue. Little dust wads collect in there. There is a little fan that sucks air past the thermistor from the cabin thru a port. On a Brit Volvo site, they spec out the actual thermistor value. Lost info.

[oragex]

I've noticed that the engine coolant temp indicator seems to be much lower than normal; just 1-2 notches above minimum. I'm in Seattle, and it's typically in the 30's or 40's in the winter.

After 20 min driving it should be and stay right in the middle. If if doesn't go up there or if it drops on the highway, the thermostat is stuck open. If it's the original 15 yrs old, most surely it's busted, they stuck open after 10 years. Another way to test it is to start the engine in the morning and idle it for 2-3 minutes. If the upper thick radiator hose that goes from the thermostat is warm near the radiator, the stat has failed.

[tboothe33]

I have a 2007 XC70 that just started having the same problem. I've read how to clean it and how to reset the CC and I will give that a try this weekend. I'm just wondering if this was ever solved for you. Summer is upon us in Virginia, but I go to the gym at 5:00 am and heat would be super nice at that time. The thermostat is fine, goes to the middle with 2 or 3 minutes, and up until last Saturday, the heat worked fine.

I read all this.

http://www.volvoforums.org.uk/archive/i ... 63988.html

[tboothe33]

Well, it appears I am the last one to comment on this. I had the heater core replaced in 2017. Well, wouldn't you know, I hit a pothole 2 weeks ago, and the heat went out again. Since my heater core is relatively new, is there something that could have come loose when I hit the pothole? It worked fine before I hit it. I'd like to think this will be an easy fix. But I do not know what to look for. 2007 XC70. Thanks for any help. Bought this one from JRL, and I love it. Just wish the heat would work. My email is [email protected] if you'd like to comment directly. Thanks.

[chrism]

I had the heater core replaced in 2017. Well, wouldn't you know, I hit a pothole 2 weeks ago, and the heat went out again. Since my heater core is relatively new, is there something that could have come loose when I hit the pothole? It worked fine before I hit it.

I wonder when they replaced the core if they disconnected the little linkages that open/close the blend doors and didn't get them reconnected properly. Then when you hit the pot hole one of them jarred loose???

They're the two flat metal "arms" in this photo:

download/file.php?id=3384

Did you lose heat on both the driver's side AND the shotgun (passenger) side?

[cn90]

My experience with 2005 XC90 2.5T with 100K miles.

Replaced with Wahler thermostat and ECT. Still lukewarm.

Replaced heater core (Behr), now nice and hot heat out of the vents.

I posted the DIYs in forum.