mitsubishi galant heater problems - only heats one side


Asked by Oct 15, 2013 at 02:12 PM about the 2004 Mitsubishi Galant ES

Question type: Maintenance & Repair

2004 mitsubishi galant only throws heat out on the passenger side and not drivers side.
(I add stop leak to my coolant about 2 weeks ago because I had a slow leak in a line.
I had issues with the a/c 2 months ago and had the resistor replaced. )

12 Answers


no I do not have dual zone climate control. line directly behind glove compartment.

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someone suggested to me that I must have an air pocket in my cooling system? I should burp the air out of the system.

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that wouldn't cause one side to throw cold and the other hot,,, sounds like your system isn't getting the vent doors all the way opened

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actuator door is the word I should of used by the way

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what happened to my original post the first one?

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not sure where your post went? I really appreciate your help here! How do I check the actuator doors?


im not sure that's the issue but sounds right,, im still looking into what I can find on this problem,, but that actuator doors are what control where the heat is going and theres other actuator doors that control whats coming out the hear or the cool and so on I read one thread that was having this issue and he said he flushed out his heater core but I don't understand how that would do anything as either the core is hot and putting out heat or its not,, not like theres a dual heater core system or anything but I guess it worked for him, heres the link if you wanna give it a shot ,,, diffent make of car but I don't think that would be an issue as they all work about the same anyways,,,,,,

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Thanks for info. Do you have any information on how I check the actuator doors?

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not off the top of my head,,, do you get even temps when you switch to ac ?


I get even temps on a/c


I found an article of someone that burped the cooling system. Curious what you think of this as a possible solution? shi/5sage-mitsubishi-montero- limited-03-mitsubishi-montero.html


Just in case link doesn't work: Customer Question I have an 03 mitsubishi montero, when its cold out side the heater only blow warm air out of the drivers side vents, cold air out of the pass side. it does not have dual zone heating. hopefully someones seen this before. Expert: Doug C. Hi, You have an air pocket in the cooling system. When this happens, the heater core is where it gets trapped, and due to the placement of the core, the interior of the car gets hot air on one side and cold air on the other due to the air being directed across 'empty' sections of the core. To correct this, simply burp the air out of the cooling system. You can do it the old fashioned way by running the car with the cap off the radiator, adding fluid as necessary as well as using the air bleed screw on the thermostat housing. I prefer to use a radiator funnel which attaches/seals to the radiator fill neck and allows you to raise the high point of the cooling system, making it easier for air to escape. Then just run the engine at a fast idle until no air escapes any longer and you have hot air on both sides of the dash. It is important to check afterward that you have no leaks as well. While it is possible to lose small amounts of coolant that add up later, or to have 'acquired' the air pocket through maintenance (water pump replacement or coolant service for example) that was not bled properly afterward, you want to be sure it did not come about from a leak that needs fixing. Ask Your Own Mitsubishi Question Customer: having hard time with air pocket. filled vehicle with vac system ran till hot with radiator funnel and have it with the front end 2.5 feet highter in front, drove it 3 time to temp then let it cool completly down. reving the motor or not there is no heat on pass side actually cold air and drivers side is so hot you cant hold your hand right on the vent for very long. its just like when a vehicle has dr and pass heat controls and one side is broken. but i only see one heater mode door motor Expert: Doug C. Thanks. Has there been any unusual happenings with the vehicle specifically the AC system? Any strange noises or anything of the sort, apart from what you have already told me? Is there anything unusual looking inside the coolant recovery tank? Doug C40851.9701469097 Ask Your Own Mitsubishi Question Customer: no noises, coolant looks good, recovery tank is actual pretty clean in side. this one has been odd for me and im stuggling with how much temp change there is in the 2 vent almost side by side? Expert: Doug C. Thanks. The temperature split happens at the heater core just inches from where the air flow is diverted and runs two separate channels even to the center vents. This is still most likely going to be an air pocket problem. The only ways you can have hot air on one side and cold on the other is if there is an air pocket, an obstruction in the air box, or an obstruction inside the core. The heater core lays horizontally in the air box, and is located above the evaporator core. The blend door is also horizontal, the length of the core; it is not possible for it to partially block one side at all. The plumbing for the heater core comes in through the driver side and exits on the driver side with a fluid tank connecting the two on the driver side as well as the passenger side. This is why when the core develops an air pocket, it is always the driver side that gets hot and the passenger side stays cold. Further, the reason the passenger side is cold is that the air is directed through the evaporator first; it does not bypass the evaporator when the heat is on. With no hot coolant in that side of the core, the air remains cold from the evaporator on that side before it is diverted through the vents and comes out cold as well. It is possible to have a physical obstruction inside the air box, however this is very unlikely in your situation for a few reasons. First, there will normally be an event or a noise before this occurs, as something has to break off/fall into the area to block the heater core. The other problems with this are that you would have reduced air flow, and not cold air since there is still air crossing an assumed hot core, just not reaching the dash registers. This is not the case for you. An obstruction below the core is not likely either, as since the air flow is forced through the evaporator, there is no way for debris or rodents etc to manage to get past the evaporator but stop at the heater core... just not possible. The potential for an internal blockage of the core is pretty good, as it will cause the same symptoms you have (again cold air from the evaporator would not be heated through the coil and come out as cold air on the passenger side registers). The problem with this scenario is that you do not notice any signs of sludging so far, which would be more than a little evident long before the core plugged up. If this was a newly purchased vehicle, I would suggest that perhaps the recovery tank was replaced to hide the coolant sludge issue, however it would still be fairly obvious looking into the radiator cap opening as well, and I doubt anyone would go the expense of replacing the radiator to hide something like that as most people wouldn't even think to look at that when buying a car. I would keep working at getting the air out; using the sealing funnel with the heat on full and engine tached up to at least 1800rpm, preferable 2500rpm but watch the funnel level as it will rise when you rev this high. Allow rest sessions periodically; I have had particularly difficult units take an hour of fighting to get bled out, and just driving the truck will NOT help, as once the system is sealed with the cap on, the air will collect at the heater core no matter what; it is just the way this system operates unfortunately. If you are absolutely 100% certain there is no air in there, you will need to start going into the dash to inspect the core itself. I would still place all my chips on a particularly difficult air pocket. These vehicles are known for difficulty clearing these and end up clearing these up for other shops on a regular basis as well. While these trucks do clog up the heater cores as well with the same symptoms, I don't suspect this is going to be the case since you have no signs of sludging in the recovery tank. Doug C., ASE Certified Technician Category: Mitsubishi Satisfied Customers: 5166 Experience: Mitsubishi employed and Factory trained ASE certified technician Doug C. and other Mitsubishi Specialists are ready to help you Customer: thank for you time and the explanation i will use the funnel again tomorrow and if i cant get it we will look into the heater core Expert: Doug C. No problem at all... be persistent, they can be real buggers. If you really can't get it and think it's air tight, you might want to pull a radiator hose off and check inside to see if there is any signs of sludging present that would of course be in the core as well. I really feel you will be able to get an air pocket cleared from there though and be good. Good luck! If you need any further help just let me know. Ask Your Own Mitsubishi Question

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