Question about heat

[ralliart610]

I have a 92 protoge with 240,000 miles. Winter came and i found out it doesnt have heat. I replaced the thermostat, checked that the water pump is working, flushed out the radiator and heater core. The car gets to normal running temperature and i get heat sometimes. It will work then all of a sudden it will get cold, and temp on the guage stays normal. I checked the hoses on the heater core with a temp gun and both inlet and outlet are the same temp. Is there a sensor somewhere that could be bad? I bought this as a daily to keep miles off my Mitsubishi, but its really cold in the winter. Any help would be appreciated. Thanks.

[vw.fe2o3]

Seems like the blend door control lever linkage controlling the air flaps at the air box has popped up as an occaisional problem. You might have to do a good impression of a pretzel and contort yourself to check behind the dash for that, but I'd start there since the temp gauge is normal, heater hoses are both hot and your fan continuously blows.

[ralliart610]

Ok thanks. I'll try to look into it tomorrow. Do you know around where to check? Should i go from the drivers side or passenger side? Hopefully i wont have to pull the dash, I hate dealing with interior.

[Mazda_Powered]

i don't mind interior work, just not in the winter haha.

just verifying, your inteiror fan works on all the different settings right? if yes, then it does sound like something is either blocking your HVAC system or one of the doors for the cold air could be jammed open blocking the hot air door from opening...

you'll wanna remove the lower dash plastic under the wheel to see where the cables go and you can stick your hand in, and you just follow the cable that goes from the heat control (cold to hot) and it'll lead you to the door system.

[ralliart610]

Ok, ill try to look at it tomorrow. Yes, I can adjust the fan speed. I was driving and the air was warm, then 10 minutes later it was cold. Its like a gamble driving that car. In the middle of driving it goes warm to cold or cold to warm. Today i was lucky enough to have heat the whole time i was driving.

[D323]

I have a 92 protoge with 240,000 miles. Winter came and i found out it doesnt have heat. I replaced the thermostat, checked that the water pump is working, flushed out the radiator and heater core. The car gets to normal running temperature and i get heat sometimes. It will work then all of a sudden it will get cold, and temp on the guage stays normal. I checked the hoses on the heater core with a temp gun and both inlet and outlet are the same temp. Is there a sensor somewhere that could be bad? I bought this as a daily to keep miles off my Mitsubishi, but its really cold in the winter. Any help would be appreciated. Thanks.

I wouldn't waste time checking the blend doors. When normally working, one hose feeds hot coolant, the core blows air over it and the coolant will be cooler as it returns to the block.

You say you flushed the core and radiator... did you flush the core specifically, or just flush the *system* and assume since the core is part of the system it got flushed too?

Pull the heater core hoses. Use a blow gun to force air into one hose and then the other. If there is a restriction it might dislodge it. At least you will know if the core is plugged if nothing comes out of the other hose.

Pulling the heater hoses and forcing air through them is a lot easier and quicker than pulling the dash to remove the air box.

[vw.fe2o3]

I wouldn't waste time checking the blend doors. When normally working, one hose feeds hot coolant, the core blows air over it and the coolant will be cooler as it returns to the block.

You say you flushed the core and radiator... did you flush the core specifically, or just flush the *system* and assume since the core is part of the system it got flushed too?

Pull the heater core hoses. Use a blow gun to force air into one hose and then the other. If there is a restriction it might dislodge it. At least you will know if the core is plugged if nothing comes out of the other hose.

Pulling the heater hoses and forcing air through them is a lot easier and quicker than pulling the dash to remove the air box.

Not saying he should remove dash and pull the air box, just suggest to trace the linkage from behind the temp setting lever to the air box control point. You can do that by just removing some underside trim, look up and feel around making sure the levers move as the slide is moved. Could be just a loose/broken link that he can reattach.
I suggest that because both hoses are the same hot temp, so coolant flow should be going through the core but are not being cooled by some air flow. Plus, a few people have posted bad door linkages before in other threads.
Hopefully an easy fix.

[D323]

Not saying he should remove dash and pull the air box, just suggest to trace the linkage from behind the temp setting lever to the air box control point. You can do that by just removing some underside trim, look up and feel around making sure the levers move as the slide is moved. Could be just a loose/broken link that he can reattach.
I suggest that because both hoses are the same hot temp, so coolant flow should be going through the core but are not being cooled by some air flow. Plus, a few people have posted bad door linkages before in other threads.
Hopefully an easy fix.

he didnt say same hot temp, just same temp. If they are both hot then yes thats a possibility, but if not and both are cool (cooler than the radiator hoses) then its likely a clogged core.

As you said, hopefully its an easy fix for him.

[Jmb323]

pull up the carpet a little and check around the heater core for leakage... just a idea ive broken 2

[ralliart610]

Sorry, i forgot i posted this in here. The hoses coming from the heater core were both the same temp. I cant remeber exactly what it was but they were both hot. I found no leakage from the heater core, and i can hear the "flap" open when i try to use the heat. Its really a hit or miss with this, sometimes i have good heat, sometimes i dont. And before i did a coolent flush, I removed both hoses from the heater core at the firewall and put pressured water through it. As fast as it was going in is as fast as it was coming out. Ive had a h22 accord, 99 GSR, 97 GSX as well as plenty other modded cars that I've worked on but this really has me stumped. Thanks for all the help. I think tomorrow im gonna put some cardboard in front of the rad to see if that does anything. I really dont now what could be causing this. I bought this for a winter beater but looks like its gonna be a warm weather vehicle. lol

[vw.fe2o3]

Sorry, i forgot i posted this in here. The hoses coming from the heater core were both the same temp. I cant remeber exactly what it was but they were both hot. I found no leakage from the heater core, and i can hear the "flap" open when i try to use the heat. Its really a hit or miss with this, sometimes i have good heat, sometimes i dont. And before i did a coolent flush, I removed both hoses from the heater core at the firewall and put pressured water through it. As fast as it was going in is as fast as it was coming out. Ive had a h22 accord, 99 GSR, 97 GSX as well as plenty other modded cars that I've worked on but this really has me stumped. Thanks for all the help. I think tomorrow im gonna put some cardboard in front of the rad to see if that does anything. I really dont now what could be causing this. I bought this for a winter beater but looks like its gonna be a warm weather vehicle. lol

You say you can hear the flap open, but have you really visually checked the linkage under there? There is another current thread going on where that was the problem. Check it out:

http://www.wihandyman.com/forum/showthread.php?t=50970

If you get down and look up above the accel pedal, you'll see the cable and plastic linkage on the side of the air box. You don't have to remove anything, just get a flashlight. Slide the hot/cold lever back and forth and watch how it moves, making sure it moves completely in each direction along the slots and without a bunch of wobbling.
No heat in the winter is the suck. I have a 74 vw w/o heat and it doesn't log a single mile in the winter months.