I was playing around with the gears on the hvac unit because of the knob problem, and I had removed the circle gear cleaned some dust off (useless). I was turning the circle gear by hand to see how hard it was to turn and I think I had it on cold but because my ac compressor has an insane amount of pressure in it the ac isn't working properly so it so I don't know which way to turn it because it was the summer when I did this and decided to wait until it was cold long story short my heat is not working any ideas. Is this just coincidence? Inwas changing my o2 housing and obviously lost a lot of coolant could it be because I didn't put enough coolant in or maybe bad thermastat? Amy suggestions would be apreciated!

 

It could be that there is not enough coolant in the system but you mentioned that you touched the hvac controls and the gear on it. I personally would double chec because there is a little small piece of plastic that pulls the leaver back to make the air go into the hot zone.

So double check and play with the gear itself manually if you feel heat after you turn the crank manually in the opposite direction that could be the problem becuase I had that issue lastyear.

 

You need to make sure the flapper doors are all funcitoning and opening/closing. If a door is stayng shut it can not allow heat through the vents. Make sure that whatever gears you messed around with are still operating whatever they were operating, correctly.



Low coolant can cause it as well, make sure its topped off and there are no air pockets in the system. Top off the radiator, close the cap. Top off the reservoir, leave the cover open and rev it to 1800 rpm or so for a few min, with the defroster on max heat. after its warmed up check and see if sucks in more coolant or if heat starts coming out. G/L

 

I was turning the gear by hand because I just change it from hot to cold by hand. You can hear the flapper opening and closing so I'm sure that's working. I'm going to add coolant I know that's low but just wanted to get some input to see if it could be other things as well thanks for the responses. If the coolant doesn't work it's back to the drawing board.

 

I, too, have this issue...I have a crazy amount of pressure in the A/C system, but no air conditioning, and no heat. It gets colder when I turn the fan higher, even on "hot" temperature knob placement. I'm all like "WTF?" cause it's like 34* in the morning now and all of a sudden my evo decides she wants to make me suffer the temperatures (no a/c in the summer SUCKS). My coolant is new, topped off, with new radiator and thermostat. My water temp gauge also tends to fluctuate between mildly cold to normal, but not hot. All of this began after replacing a blown head gasket and stuck thermostat. Ideas?

 

clogged or restricted heater core? check your heater hose lines going to and from the firewall. feel them when you have the heater on and the car is warmed up. You should be able to feel the fluid flowing through both of them.

You say your a/c pressures are 'crazy', what exactly does that mean? I take it then you hooked up gauges to your a/c system, then what were the low and high side pressures with the a/c on max cold?

 

I will check my heater hose lines today. I was thinking the car needed a heater core flush? I did one when I owned my VW, but not sure if the Evo requires the same general maintenance or if I should just replace the heater core all together (high cost, PITA, not exactly on my top list).

Low pressure side of A/C was around 190 with max cold at about 80*F ambient outdoor temperature. Should be around 140-150 at that temperature. I did not check high pressure side because of injury risk. I do not have the tools to check that side.

 

low side should be ~30 psi, high side ~150-180ish psi. You have high psi for the low side. Maybe expansion valve is faiing?

 

My heat works great now I just was alittle low with coolant it wasn't even that low which was weird I guess just enough to be a pain in the a**! Evol keep us updated on the heater core lines and heater core