HVAC heat blows warm/hot on drivers side, cool/cold passenger side (warranty issue)

[Daox]

You need to get one of those inspections scopes so you can get a look inside without tearing anything apart, and look inside the heater core. Where is the electric heater, any chance it's set up just to help the driver?

How about the possibility of air trapped in the core?

When your SG2 was saying 195d water temp, did you check the temp at the heater core? Maybe a water pump flow issue.

An inspection scope would be great.

The electric heater is right after the heater core. It is the full length of the heater core. I don't get as much heat on the passenger side of the windshield defroster and foot well, not just vents. So, everything splits off in the middle to each side.

When I bled the air out of the system, I specifically jacked the car up on the driver's side to get any air out of the heater core since the connections are on the driver's side. I did get a few little bubbles out.

I have not checked the water temp at the heater core, or the lines going to the heater core. However, I have sat there and revved the engine and it makes absolutely no difference in heat output to the passenger vents. So, I assume it is not a flow issue, or the flow from the engine isn't an issue. Flow through the core could possibly still be an issue.

Good ideas though, thanks!

[Daox]

I also re-tested my air vent temperature. This time I used my digital multimeter. It has a k-type thermocouple temperature sensor. This allowed me to measure the actual air temperature, not just the plastic vent temperature.





For reference, the ambient temperature was 25°F, and the coolant was about 170°F.

Here are the readings I got:

125 - 98 - 89 - 79

[Top_Fuel]

I honestly didn't spend much time checking the 2 center vents...so I might have a variation there. I may just get 4 thermometers and drop them into each vent so I can read the temps simultaneously. At this point I'm still assuming that this variation is a "feature" of the Mirage.

Maybe we can get a few more people to run this test and post results.

[Daox]

Thanks so much for doing the testing Top Fuel!

I agree it would be great if a few others could run this test. I would really be interested in seeing how the 2017 model does since they changed the heater case and blower motor (more info below).

So, three of us have had this issue now. Two 2014s, and one 2015. I agree, this is starting to look to me like a 'feature' / design flaw.

I have evaluated the parts list for the heater system in the Mirage over the years, and no surprise, 2014 and 2015 are identical. Several changes were made in 2017 though...

Here is the diagram and parts list. I haven't included the numbers on the parts list because they don't correlate between the 2014/2015 & 2017. However, we can still tell that they haven't changed the heater core part number, but they have changed the case that the heater core goes into. Perhaps the new one seals better around the heater core? They also have a new blower motor. It is possible they simply slowed the fan down to 'fix' the problem. At lower fan speeds, the temperature differential would be much lower.

[Fummins]

I didn't read the entire thread, do you only get cool air while on vent? Do defrost and floor blow warmer air? Are you sure your thermostat is opening all the way? Does the air blow normally, like enough force? I had a vehicles that had so much crap(leaves and dirt) accumulate at the evaporator that hardly any air could flow past it and to the heater core. That caused very little heat and poor air flow. The only fix was replace or remove the evaporator core.
The dash isn't hard to remove on these cars. I pulled on in under an hour. Pull the console, steering column and find the bolts holding the edges to the side of the car. And there are some along the front edge near the windshield too I believe. I had to pull the dash out when a driver dropped a pen down a vent and it made it's way into the heater box.

[Daox]

Yeah, you get cool/cold air on the right side no matter if its on vent, defrost, or foot.

I know my engine is getting fully up to temp because I have a scangauge that shows me my coolant temperature. I've also never overheated. Highest coolant temp I've seen is 200F.

Air does seem to blow evenly out of all vents, and it does seem to blow a decent amount of air.


Good to know about the dash! I plan on inspecting things better later on. My cabin filter was full of junk. I kind of doubt too much got past it, but I wouldn't eliminate it as a possibility. This issue you had was on a Mirage?

[01-7700]

Thanks so much for doing the testing Top Fuel!

I agree it would be great if a few others could run this test. I would really be interested in seeing how the 2017 model does since they changed the heater case and blower motor (more info below).

So, three of us have had this issue now. Two 2014s, and one 2015. I agree, this is starting to look to me like a 'feature' / design flaw.

I have evaluated the parts list for the heater system in the Mirage over the years, and no surprise, 2014 and 2015 are identical. Several changes were made in 2017 though...

Here is the diagram and parts list. I haven't included the numbers on the parts list because they don't correlate between the 2014/2015 & 2017. However, we can still tell that they haven't changed the heater core part number, but they have changed the case that the heater core goes into. Perhaps the new one seals better around the heater core? They also have a new blower motor. It is possible they simply slowed the fan down to 'fix' the problem. At lower fan speeds, the temperature differential would be much lower.

a feature wouldn't change operating behaviour from year to year would it ? My heating system was fine last year - just noticing the loss of temp this year.

[Fummins]

Grasping at straws here. My only guesses are heater core still blocked or blend door malfunction? I'm really thinking the rh side of the heater core is plugged I've used some industrial drain cleaner with great results but that was in a b2200 with a copper heater core.

All of our cars at here at work have manual temp controls. Does the automatic controls on the mirage allow you to change the temp for driver or passenger?
It doesn't look like the tubes are any longer to the rh vents. If anything they might be shorter going off the picture on page 55a-51 in the service manual. I can't figure out how to post the pic.
Wonder if you could stick your probe down the center 2 vents and use an inspection camera to see the core. Might give you a good idea whats going on down there.

[Top_Fuel]

It doesn't look like the tubes are any longer to the rh vents.
If anything they might be shorter going off the picture on page 55a-51 in the service manual.

[01-7700]

Grasping at straws here. My only guesses are heater core still blocked or blend door malfunction? I'm really thinking the rh side of the heater core is plugged I've used some industrial drain cleaner with great results but that was in a b2200 with a copper heater core.

All of our cars at here at work have manual temp controls. Does the automatic controls on the mirage allow you to change the temp for driver or passenger?
It doesn't look like the tubes are any longer to the rh vents. If anything they might be shorter going off the picture on page 55a-51 in the service manual. I can't figure out how to post the pic.
Wonder if you could stick your probe down the center 2 vents and use an inspection camera to see the core. Might give you a good idea whats going on down there.

Grasping at straws is good. It helps to consider ALL possibilities and not to focus on anything in particular unless it can be ruled out by visual inspection.

The Mirage does not have separate heating zones but who knows if AC is fed in one side and heat in the other. Right now it's a black box until someone takes a look inside.

I'm going to try to find a scope locally but don't have a lot of hope in that, maybe Harbor Freight.