2000 V70R - Only Mild Heat in The Cabin

Bluevanacd2005 · Post by **Bluevanacd2005** » 25 Nov 2015, 15:55

Good thinking, but alas... It was turned to '0'

Bluevanacd2005 · Post by **Bluevanacd2005** » 25 Nov 2015, 16:34

Although where does this flap reside? The switch may be set to '0' but maybe that flap is stuck open? I assume this is servo controlled too? I'm thinking it may be the flap in the duct by the blower discharge...

Post by **scot850** » 25 Nov 2015, 17:14

The flap for the cold air intake is behind/above the fan motor. However, if you pull the glove box out (you need to do this to remove the lower RH under dash shroud) you can see the servo motor side on to you to the left of the fan motor. There is a lever from that to the flap, and that can break. But by doing this you can see if the motor/flap is opening or moving by moving between re-circ. and fresh air setting. If the arm is broken, you can remove the servo motor by removing 1 small Torx screw at the front and it slides out toward you.

The other thing if you haven't already checked is the cabin temp sensor. See this thread where I wrote how to get to it. Worked for this enthusiast!

https://www.matthewsvolvosite.com/forums ... =1&t=72802

Good luck!

Neil.

Bluevanacd2005 · Post by **Bluevanacd2005** » 05 Dec 2015, 19:14

Alright.. I finally got back to this. I put the servos back in but left the dash apart. As far as I can tell, all the flaps work right and none of the linkages are broken or stuck.

There was a mention of the cabin air filter. I have never changed this, but I also couldn't find one to change. Where is it located?

Continuing to troubleshoot... I was going to replace the thermostat, but as I mentioned I have no engine temperature issues and it warms up quick. Also I cannot hold my hand on the heater core piping because it is so hot (both of them). So I passed over this for now.

Moving on, I took the four screws out of the plastic housing holding the core and let it drop until it was on the center hump (giving me just enough of a gap to see the core and stick a finger in to touch it). The drivers side felt warm, but the passenger side did not. It looked very clean on the side I could see.

So at this point, I am leaning towards replacing the core. It seems to have uneven flow through it? Maybe the coolant side is mostly plugged?

Or am I still looking at the possibility of it being air locked? This does seem like a possibility because the tubes enter and leave on the bottom. I guess I should try bleeding it first.

Thanks for the help!

Spenser

Post by **jimmy57** » 05 Dec 2015, 21:25

I could barely tell the difference on a 35 degree day in my 98 XC70 with recirc air or fresh air. Volvo strategy is fresh air (colder air) in heat settings. Recirc setting allows humidity build up since no fresh air is exchanged. Recirc should have no bearing on this problem as described. If both hoses are uncomfortably hot to touch then there is no air lock and block of coolant flow in heater is unlikely. Air path blockage would go to near the top of the list.
When you removed temp mix door servo could you hear the doors hit full open and full close? Still broken doors are less likely as both breaking at the same time is not highly likely. This heater core has both fittings on the same end. In this arrangement there is a "wall" that separates the end tank so the flow will be across 1/2 of core to opposite end tank and then back across the other 1/2 to the end tank with fittings. If the wall breaks (corrodes on aluminum end tank versions) then the coolant will not go through core and you have hot hoses to/from the heater core.
With the price of these heater cores and no harder than they are to change you have the right idea with replacing it. Even if it was air blocked it would be a shame to remove it and blo it clean only to have it rupture on the normal schedule that these heater cores expire.

Bluevanacd2005 · Post by **Bluevanacd2005** » 06 Dec 2015, 12:00

Heater core ordered

Bluevanacd2005 · Post by **Bluevanacd2005** » 12 Dec 2015, 02:20

Installed the core tonight. It definitely seems to have solved the problem! I have good heat now, just in time for winter.

On a side note: the air side of the old core was perfectly clean, not even a spec of dust on it. From this I can only assume the division wall inside the coolant end is rotted away. Makes sense now that I think about it... Running the engine RPM up gave me heat for as long as I kept it up. This must have increased flow through the core and forced a little coolant up through the tubes. Then when flow returned to being lower, the coolant would just flow in and back out through the rotted wall, bypassing the tubes. I intend to cut the old core open when I can catch a little spare time to confirm this...

Thanks again for the help!

Spenser

Post by **abscate** » 12 Dec 2015, 03:41

Cool...I mean...hot! Will be interesting to see the guts of a core and see the wall problem in the flesh.

Bluevanacd2005 · Post by **Bluevanacd2005** » 12 Dec 2015, 15:45

Well... The hypothesis was right! The funny thing is there is no metal in the ends, only plastic. The plastic apears to have broken off a while ago. Very interesting!

Spenser

Post by **scot850** » 12 Dec 2015, 16:14

Glad you finally found a solution Spenser!

Neil.

2000 V70R - Only Mild Heat in The Cabin

Re: 2000 V70R - Only Mild Heat in The Cabin