Driver's side blows heat, passenger doesn't...

Hey guys, I've noticed in the past couple weeks that when I use the heat in my car the drivers side will blow hot and the passenger side blows way colder. But it only happens most of the time. Sometimes the passenger side will blow warm for a little. I figured now would be the time to figure this one out before it gets chilly all the time.

typically this is due to a clogged heater core. the pass side of the core gets clogged first.

 

you might try flushing it out. remove tmic and you will see the 2 heater hoses going to the firewall. remove those and flush out with a garden hose. some fill the core with clr, let sit for a few minutes, then flush again with water. reconnect everything and test it out.

typically this is due to a clogged heater core. the pass side of the core gets clogged first.

 

you might try flushing it out. remove tmic and you will see the 2 heater hoses going to the firewall. remove those and flush out with a garden hose. some fill the core with clr, let sit for a few minutes, then flush again with water. reconnect everything and test it out.

 

??????????????????????????????????? What on earth are you talking about? There is no "driver side" and "passenger side" to a heater core. Flushing it is not a bad idea but there is only one heater core. I wouldn't do the CLR thing. Hydrochloric acid and aluminum don't get along well at all.

 

OP, there is a blend door for heating/cooling on each side (DS & PS) and most likely either your PS blend door is sticking shut or is broken and occasionally will open due to bouncing around and knocking itself into position to allow it to still align enough to work once in a while. If you have heat on one side, the heat is there, it's just not coming out of the proper vent side. I would bet that if you put the A/C on the floor on the PS, you won't have that either. There is a mode door actuator that could possibly be bad too. Check around under the dash.

I've been yelled at

 

Trust me about this, it happens (pass side heat), others have posted about it, others have had success using this method (including me recently - first hand experience). True, there is only 1 heater core, but the ducting for the driver side and passenger side goes through different halves of the same core. The passenger "half" of the core is on the bottom, and tends to usually collect all the sediment first and become clogged first.

 

Here is an example of this: link

That's an example of another thread touting the same thing-not information as to how the system works. The heater core does NOT have a driver side and passenger side. Go look at one at the parts store. Yes, they can become clogged due to residue within the engine block finding it's way to the heater core and Chryslers are famous for this happening, but there is not a defined side.

 

The heater core fits across an opening in the heater plenum box, in front of the A/C evaporator core. The air and the heat or A/C is pulled through evenly by the blower fan. The heater core is a cross flow design, so if it does begin to become contaminated, it fills at the bottom first as the detritus settles. This happens just like it does in a radiator or a water heater in your house but it does not settle on one side or the other. That's not possible. What can happen is as the sediment settles in, it can restrict the flow back to the engine and eventually cause overheating issues due to the coolant not actually recirculating.

 

Look at an exploded view on vacation pics and you'll see exactly what I mean. The division of DS and PS is based on a series of flapper doors on the plenum that open and close as you move or activate your zone controls and what is wrong with this vehicle is that the PS flapper door is either sticking or broken. There is a single opening into the plenum box for the heat and A/C with no division until it reaches the outlets/flapper doors.

I appreciate what you are saying, but I'm not just parroting theory from another thread, this actually worked for me! I had no heat on passenger side, and heat worked fine on driver side. I did the suggested steps for flushing the heater core, and INSTANTLY it was working on both sides. I don't know what else to say. It worked for me, it worked for frank_ster, and others.

 

Sorry to argue. Maybe the OP can try it if he wants, and report back his findings. I do realize it could be a blend door as well, it's just less common, and flushing the core is super easy.

Just curious? "clr"??? Chlorine? or???

Just curious? "clr"??? Chlorine? or???

 

http://www.jelmar.com/CLRbasic.htm

 

You don't have to use it to flush a heater core. Plain water works. Also there are other solutions available specifically to flush cooling systems. It's just that CLR came up a few times on this board for cleaning the heater core, i already had some, tried it (only let it sit for a few minutes, then flushed it out with water) and I've had heat working since then from both sides.

OK, then I see that as a last resort when nothing else works.

 

As for a single core but not working on only one side - it depends on how the air flows post core and how the deposits impacts the core, so even a single core may result in difference in temperature between the sides in the car.

wow - u just changed ur avatar. nice!

I had the exact same issue with our '05 legacy, heater core flush fixed it. Blew warm air on drivers side, but no warm air on pass side. Seems to be a common issue, and affects only the pass side for whatever reason.

 

Subaru's coolant conditioner is essentially "stop leak" to mask head gasket issues, if your coolant system has ever been opened up it will congeal and cause blockages in the system.

So check the doors under the dash and flush the heater core? Thanks guys!

Heater core flush worked. It was all nasty in there. Thanks guys!

glad to hear it!

hey guys having this problem as well w my 07 LGT...anyone have a few pics or a step by step on how to do this fix?....thanks...

Flushing the core - there are two hoses with an outer diameter at about 1 1/2" or so going through the firewall. Disconnect them at suitable points, flush with fresh water, e.g. with a garden hose. Go both directions, and be prepared to get wet!

 

Avoid too much pressure.

If I would've thought about it the other day when I did it I would've taken pictures!

Same problem with mine a while back.

 

A standard "cooling system flush" didn't do the trick for me. I asked the dealer to flush and back flush just the heater core and it worked.

 

I don't know why it always seems to be the passenger side with our cars but that's what it is.

Question this happened to me last winter (late Feb) i just rode it out as I dont have any passengers but now it is getting cold again so I want to tackle this. What is the best method to connect the hose to the I/O of the core? clear tubing?

 

Also after the core flush wouldn't you need to burp the whole system ? Also isnt plain water bad for the system? I thought we should use distilled water for flush and 50/50 mix to fill.

 

Any help would be great I dont want to pay Stohlman $179.99 to do a coolant system flush and refill and they skip the core.

Probably many ways to do it. I just used a piece of heater hose of similar size, connected one end to one of the heater core fittings, and clamped the other end to a garden hose's threaded output. I opted to also take another piece of heater hose, connect to the *other* heater core fitting and route it out of the engine bay so I wouldn't make a mess when flushing.

 

Doing it this way (flushing the heater core only), you are only putting tap water in the heater core (and CLR if you decide to use that). When you are done flushing it, you can easily blow out any remaining water with air (even using lung power). Reconnect everything, top off the system with distilled water/antifreeze.

No problem with tap water for flushing, and in general tap water isn't a problem unless you have unusually high levels of chlorine or other contaminants in it.

 

Just make sure you use fresh anti-freeze that works for aluminum and you shall be good to go. Re-filling with the old fluid is bad because it's like brake fluid - when it gets old then it gets bad.

Does any one know how tho change the the blend door actuator on the passenger side without removing dash. I know they are prone to failure?

Had this problem.. manifested in passenger side not getting any heat. I could tell immediately by turning on the heat and feeling warm air coming out on the dr side and cool air coming out the pass side.

 

I back-flushed the heater core by removing the input/output hoses on the firewall, blew out the core using compressed air on the outlet side, and then installed the hoses in reverse and drove for a week.

 

Here's step by step what I did:

 

1) let the engine cool - don't want to get scalded by hot coolant

 

2) remove the engine cover and TMIC so you can get to it easily

 

3) placing a rag under the two tubes almost centered on the firewall, using a pair of pliers, compress and slide the hose clamp down the tube about 2" - enough to back it off the internal pipe.

 

4) Use a set of long jawed vice grip pliers to clamp off the hose further down the hose. This to prevent draining coolant. It is high enough in the system that it may not drain, but I clamped anyway because I have them. Not too tight that would cut the hose when it squeezes. You may not need to do this step.

 

5) With the rag under the hose/pipe area, back the hose off the pipe. There will be leaking of coolant as it comes out of the pipe.

 

6) Follow the same instructions as #5 for the bottom hose. It's easier to get to the bottom one with the top one cleared out.

 

NOTE: The top pipe is the Outlet for the heater core, bottom is Inlet. This is reasonable if you think about air in the system pooling in the heater core if the top was the inlet and bottom outlet. The top outlet sucks out air to be pooled in the radiator.

 

7) Blow compressed air through the top pipe - the outlet - to push back any gunk. Make sure to keep the rag under/in front of. but not plugging, the lower pipe as it will blow out coolant and debris. I have a portable air tank I used for this.

 

8) When you think you've done enough, reinstall the hoses BUT, place the hose off the top pipe onto the bottom pipe and slip on the clamp.

 

9) Place the bottom hose on the top pipe. Now you have reversed the flow of coolant through the system. Theoretically, this will back-flush the system. I drove it like this for about a week.

 

10) When you've back-flushed enough, run through the steps above to swap the hoses back to their original orientation.

 

NOTE: after both processes when you've removed the hoses and coolant drains out of the system, top off your coolant reservoir. The system should purge itself of air and draw in the necessary coolant from the reservoir. I didn't have any temp issues during any of this, but did notice a little coolant drawn off after a couple of heat/cool cycles. With the hoses clamped off it didn't loose much from the core pipes.

 

There is the risk that if the heater core is full of hard deposits like rust that back-flushing the debris into the system will damage it. I figured it would find its way to the radiator and settle down into the bottom like the rest. I've changed my radiator about 20k mi ago when the top plastic separated from the AL fin core, so it should have room for debris. And I change out my water pump/thermostat about every 100k miles when I change out the timing belt. Better safe than sorry.

 

edit: re blend door... I thought this was my problem first, began to look into removing the interior paneling to get in there and saw it will be a PITA. As I was searching for further info on removing the panels to gain access, found the thread discussing blockage on the heater core manifesting as pass side cold. It was a lot easier to do this flush than get to the blend door - at least for me. Tried this first and it seemed to work. Only time will tell whether it is a long-term fix or if it will simply clog back up.

glad you found this before tearing apart your hvac! mine has been doing fine since this flush procedure about 2 yrs ago.

 

also note that some have said that even new-ish, the pass side gets hot, but not quite as hot as the driver side. this being said, if the passenger side doesn't warm up at all, this procedure is definitely worth a shot!

Quick question....

 

So when we detach the heater core hoses, doesn't it let air get into the cooling system?