2006 V70XC Only warm heat when heater on high.

[Bluegrassxc70]

Thx for the replies everyone. I am pretty sure it Is not temp sensor related. I have verified it is clean, it does not look broken, and the system regulates temperature properly when on the colder settings.

I do not hear any blend door clicking or clunking. I have observed their motion with the side panels off and everything seeems to be smooth.

I am leaning toward an issue in the heater core. Possibly a bypass in the core itself.

Any additional thoughts or tests I can do to verify?

Thx for the help everyone.

[Rattnalle]

The fact that there is a temperature difference between the two tubes when heat is on does point to a clogged heater core since it's a full flow system with no regulation of water flow.

However the fact that you do get heat on high contradicts this. Is it sauna-hot or just hot on high? It should be the first.

[Bluegrassxc70]

If the core was partially clogged, then I would think I get some flow through the core but not enough to warm the air sufficiently. There wold still be a delta in temp between the in and out tubes like I am seeing. I may see the same symptoms if there was a bypass (or broken internal passage in the core). In that case only part of the heat exchanger would be effective. I would expect there to be a smaller delta in temp between the inlet and outlet tubes because I am extracting less heat from the fluid as the heat exchanger is not fully utilized.

Sorry if I was not clear. I do not get ‘heat’ on high. I get Lukewarm air.

Thx everyone!!! I’m sure we will figure this one out.

[Rattnalle]

It's supposed to be a sauna on high so it does sound like the core might be clogged.

[velorider]

At this point I would replace the heater core, not to difficult. I had a similar issue of luke warm air. I replaced the heater core with one from the salvage yard and heat returned. I assume it was a partial clogged, since I had a heat differential between the hoses.

[Bluegrassxc70]

Did some more investigation tonight. Verified that the thermostat was opening properly.

I agree that it is likely a heater core issue. I’m going to order one and replace.

[dejanaleksov]

I had the same problem. I change heater core nissens part.changed tsat wahler,the old stat was stuck open, changed coolant and still no heat only mild heat.clean the t resistor in ccm, behind the air quality sensor there is a cooler wich sucks air for correct readind in the cabin temperature ,which wass clogged by dust and hair.blowing ait through it will not help. You have to get out the ccm open the cooler and clean the cooler and oil the baering.mine was not circulating air through the sensor, but that didnt help I still have no heat on cold days highway speed.than I open the tsat housing and find out that the smaal nipple on stat was not correctly positioned (small nipple should be on top facing the front of the car) fix that and still no heat.i guess this nipple will alow trapped air to get out. So I drove the car on a mountain with coolant in my car luckily, still no heat,parked the car on incline facing up.,reving full throttle 4000 rpm in neutral and she doesnt want to burp the air out.then thanks to you guys especially oragex who told us to lift the coolant reservoir up (put something inder it... Do not force it up there is a sensor that u might break) and after two winters of fighting with no heat finally she burped and burped and burped the air out after several times opening the tstat and cooling fan start up qnd cap off,watch out for boiling hot coolant will want to go out the reservoir than close cap, and after cooling fan start open slowly and air will come out several times... Top off with coolant and u will have heat if all other is in order.thanks guys I learned a lot from u...V70xc awd Cross Country 2001 aw 55/51sn

[cn90]

The thermostat is on the way out.

A brand-new Wahler tstat is about $80 on ebay etc.

I posted a DIY for my 2005 XC90. 2.5T WITHOUT removing the PS Pump.

[ssurowiec]

Did you ever get this resolved?