Narrow Down Low Cabin Heat Issue Topic is solved

Post by **velorider** » 23 Feb 2018, 14:04

Picked up this Volvo S60 a few months ago and the only remaining issue is the cabin heat. I've searched and tried to diagnose it, but have been unable to find the issue.
Diagnoses So Far:
1. Engine temp reaches normal operational temperature
2. Upper radiator hose is hot, confirms normal operational temperatures
3. Ran calibration via Dice, no codes
4. No signs of heater core leak
5. Heater core hose temperature differential between inlet and outlet seems normals, temperature of inlet does seem less then upper radiator hose
6. Flushed heater core no dirt
7. Cabin temperature does fluctuate between cold and slightly warm
8. When Recirculate is on there is a rattle behind glove box.

Any help would be appreciated. I tried locating the bend door for the temperature but not sure where to look behind dash for it and what to look for. From the slight change in temperature it does appear to have minimal function. Is there anything with VIDA that would help me diagnose this issue?

Thanks
John

Post by **Rattnalle** » 23 Feb 2018, 14:10

5. There should be very little if any difference between the hoses.

Have you checked that the fan behind the temperature sensor in the acc panel is spinning as it should?

Do you get proper heat if you turn it to max?

Post by **Rattnalle** » 23 Feb 2018, 14:16

And also you can read the cabin temperature in Vida. Does it. Match what a thermometer says if you put one next to the acc panel?

Post by **velorider** » 23 Feb 2018, 15:03

Rattnalle wrote: ↑23 Feb 2018, 14:10 5. There should be very little if any difference between the hoses.

Have you checked that the fan behind the temperature sensor in the acc panel is spinning as it should?

Do you get proper heat if you turn it to max?

Really, I thought there should be a difference because the heater core exchanges the heat into the air. I just measured the temperatures of the two metal pipe entering the heater core. The pipe nearest the firewall measured 122f/50C and the farthest from the firewall measure 156F/69c. The car was not a full operation temperature so I suspect that is why the inlet pipe is only 69c. For what I know understand, I would expect this drop as the heat is exchanged into the air.

I've attach pictures to better explain what I am measuring.

: heatcore.jpg (84.52 KiB) Viewed 3111 times

Post by **velorider** » 23 Feb 2018, 15:30

Rattnalle wrote: ↑23 Feb 2018, 14:16 And also you can read the cabin temperature in Vida. Does it. Match what a thermometer says if you put one next to the acc panel?

Thanks for this suggestion. I checked and yes it does. I've also never measured the temp of the air coming out of the vents. With the A/C on and heat to max I get about 96f and with A/C off I get 99f. Like I said I never measured it and today after flushing and calibrating I got these temps. 99f doesn't seem much compared to the temps out of my truck, but much better then I was getting before. Any idea what temp I should expect on max heat?

Maybe the flush addressed some of the issue. Tonight I'm driving up into the mountain where the temps will be in the high 20f so we'll see how the system works.

Post by **oragex** » 23 Feb 2018, 20:36

velorider wrote: ↑23 Feb 2018, 14:04 7. Cabin temperature does fluctuate between cold and slightly warm
The pipe nearest the firewall measured 122f/50C and the farthest from the firewall measure 156F/69c.

The lower pipe at the heater core is the intake, same as the rubber hose towards the drivers side inside the engine bay.

Given the engine wasn't fully warmed (about 85C), the temperature gradient between the two pipes seems to indicate the heater core is working properly.

Does this happen in manual mode, when you select one of the three 'sitting man' buttons ?

Is the temperature the same on both sides, pass - driver?

May as well blow some air - but not touch - over the tiny cabin temperature sensor behind the grid near the right temperature knob. It may be covered in dust.

Because you mention the temp fluctuation, I would rather think of CCM doors not operating properly. This can be also caused in Automatic mode by a faulty temp sensor or covered in dust.

You can see the flaps at 31:20 in this video, gives an idea how it works

The Recirculate closes a flap above the fan blower to cut the air from outside. This flap may move a little sometimes, but won't influence the temperature.

Post by **velorider** » 24 Feb 2018, 00:09

Temps got down to about 9f/-12c and the cabin temp wouldn't get above low 60f/15c. During the drive I check via vida the CCM cabin temp and measured actual temp and they matched, so the cabin temp sensor is working.

I did find the driver side temp door motor and it looks to full opens and closes. Didn't have time to look for one on the passenger. I'll check Monday.

I've tried auto, window, center, and floor seeing and the temp never improves. After today's calibration and flush things slightly improved.

Right now I'm leaning toward poor flow through the heater core. I'll reverse flush again Monday and if that helps I'll pick up a replacement at pull a part.

I'll report back later in the week.

Post by **Rattnalle** » 24 Feb 2018, 01:14

To me the large temperature difference between the hoses together with poor heat in the cabin indicates that the core is clogged. The flow should be good enough that the actual difference is quite small. With poor flow the water has more time to cool down in the heater core.

The car should easily become a sauna if you crank it up even when it's very cold out. And also at the "red" mark above the temperature scale I believe it just runs a pretty defined max heat programme ignoring all sensor inputs ruling errors there out.

Post by **oragex** » 24 Feb 2018, 07:18

velorider wrote: ↑24 Feb 2018, 00:09 Temps got down to about 9f/-12c and the cabin temp wouldn't get above low 60f/15c. During the drive I check via vida the CCM cabin temp and measured actual temp and they matched, so the cabin temp sensor is working.

I did find the driver side temp door motor and it looks to full opens and closes. Didn't have time to look for one on the passenger. I'll check Monday.

I've tried auto, window, center, and floor seeing and the temp never improves. After today's calibration and flush things slightly improved.

Right now I'm leaning toward poor flow through the heater core. I'll reverse flush again Monday and if that helps I'll pick up a replacement at pull a part.

I'll report back later in the week.

Actually, despite being some work, just pulling the core will give a perfect view of how well the doors are functioning.

Post by **velorider** » 27 Feb 2018, 19:06

Thanks oragex and Rattnalle for all the help and suggestions. I'm pretty confident it is the heater core that is partially clogged. Both bend door motors are working and the temperature does fluctuate slightly.

Today I had time to swing by the pick-a-part to pull a heater core. I have a couple questions about reinstalling. To pull the core I removed the steering knuckle and pulled it down and out of the steering column. This allowed the heater core to pull straight out. I assume installation is the reverse, making sure I align the splines so the knuckle connects with the correct orientation.

When the core is out I will double check the bend door are operating correctly.

I had an idea to do a flow test of the current installed core and replacement once installed. I'm hoping I can get an ounces per minute gravity flow so the next guy can do a simple in-car test to confirm the flow of the core. I'll report back the results for the next person.

Thanks again for all your help and suggestions.