noob with heater troubles

[wetwilllie]

Hi all,

I just traded my 240SX for a '75 '02. Best deal I have ever done.

I do have on problem, the floor vents for my heater blow warm air on the end closest to the firewall and cold air out the side closest to me. Mind you, this warm and cold air is coming out of the same vents on both floor outlets.

I have searched and haven't found anything that talks about this. I don't even know how it is possible.

The car doesn't run hot or cold. It sits just above blue all the time. I just rebuilt the heater box. (awesome tutorial by the way). The system has been bled and im confused. so very very confused.

Any help would be fantastic. I will even take pointless speculations at this point just so I have something new to try.

Thanks.

[ryanOC]

does your car have AC ?

[wetwilllie]

No A/C. And it had this problem before the rebuild. It was the reason for the rebuild. Not sure if i mentioned that.

[02hobiedave]

I just finished my rebuild and it might be your fresh air vent. Did you bench test the system first to make sure everything would close up correctly (flaps)?

I think your 75 has four sliders and mine 72 only has three my fresh air and heater valve are on the same slider the one in the middle. So when the heater valve is open no fresh air. then you can close the heater valve and the fresh air vent opens up.

Did you check for fit of the flappers while it was open and make sure all parts moved freely. Did you fix any cracks in the case? I had one that was about 4" long. JB weld is great.

Do you have your hoses hooked up for your window defroster? one more thing try going under the hood and turning off the heater valve by hand it could be your bowen cable not closing all the way. Sorry just shooting a couple ideas out there. There should only be one floor vent on each side it should open to the bottom by your foot. the other vent on that side should be round and have a hose going up to the window defroster.

Dave

[im3crazy]

Sounds like there may be air bypassing the heater core and blowing out around it with the heated air. No other reason you would have such a mixture in this simple system.

OR

Also, maybe part of the core is blocked and only the front half is heating?? I'm not sure about the coil layout on these, but it's a possibility.

[DanOKC]

Did you flush the heater core when you rebuilt the box ? If not, you can still do it in the car. I had this symptom years ago on my 74, and if I remember right, all was well after rebuilding the heater box, but I always flushed the cores. I just used a little dish soap at the kitchen sink with the spray nozzle on the sink. Try same thing with a garden hose on the car & just disconnect heater hoses & set it up so you can see when water comes out clean. Also try flushing from both sides.

[wetwilllie]

The flaps seemed to be working ok. I sealed all the cracks and had to rebuild one side of the back of the box so that is sealed well. I also had to make a new mount for the valve so it would hold still and open.

I will give the flushing a try and get back to you.

[Guest Anonymous]

I suggest using a commercial radiator flush compound - you are trying to get rid of years of mineral build-up, so you need something heavy-duty like Prestone super flush.

[Mike Self]

The lever that controls temperature has two cables fastened to it...one goes to the heater valve, the other to the cold air mixer door. The way it should work...

as you move the lever from cold to hot, the heater valve opens (allowing hot water to flow thru the heater core) and the cold air mixer door closes. So with the heater set to full cold, the mixer door is fully open, and the valve is closed. At full hot, just the opposite.

sounds like either the cables are misadjusted, or the heater valve is operating backwards (easy to do when reassembling).

Hope its something simple and you don't have to pull the heater again!

cheers

mike

[02for2]

It pretty much has to be your fresh air vent, either slightly bent to one side, or not fully closing.

I rebuilt my box last week too (seems to be the season) and I used the tutorial here. I did have to trim the foam slightly angled at the leading edge for it to close fully and make a proper seal - easy w/ razor blade.

If you're lucky, you can adjust the bowden cable at the slider control to make up any slack. If not, you'll need to pull the box.

Cheers!