In cabin heat performance=subpar

[Schrute Farms]

Car is a 93 240sx. Automatic that was converted to a manual.Here's the deal- my heat works excellently on setting '1' It works pretty well on '2'... When it is on '3' and '4' it is basically blowing cold air. Just for clarification- the blower motor is fine... I am upset with the actual temperature of the heat that's coming out of the vents... The car has 5000 miles on the rebuilt motor. The water pump is new. The coolant is the proper mixture of 50-50 water-coolant and is full. The overflow/reserve tank is full. The cap holds pressure and there are no leaks in the coolant system. The car still has the automatic trans radiator (just has the trans cooler fittings). Now my question is why does my heat suck?!?! The lines going to the heater core are a tad bit kinked but not bad IMO. I will get a picture tomorrow in the daylight. I thought that would be the problem but my friend who is more car savvy than I am says that really shouldn't matter. Any ideas? Am I the only one who thinks the heater core lines are to blame? Thanks guys

[modulation]

A few things..

#1. Most Likely there is still air in your heater core from when you messed with coolant system. Put car on ramps so radiator cap is highest, take off radiator cap, let car get up to temp and make sure heater is turned on..

If #1 isn't it (which I think it is since it's most likely):#2. There is a baffel that is moved by the vacuum system which allows the air to blow threw the heater core area or not. Perhaps this isn't working?When you move the lever from cold to hot does anything happen (noise, etc?)Or is the air like the same temp no matter what side it's on?

#3. Did you buy the car used? Perhaps they did a heater core bypass on it?

[glitched]

Hmm, my car had the same symptoms of the air temp not being warm enough on 3 and 4... however when the water pump died and I got a new one, the symptoms went away...

[Schrute Farms]

Hmm, my car had the same symptoms of the air temp not being warm enough on 3 and 4... however when the water pump died and I got a new one, the symptoms went away...

Lifetime warranty on my water pump ftw.

A few things..

#1. Most Likely there is still air in your heater core from when you messed with coolant system. Put car on ramps so radiator cap is highest, take off radiator cap, let car get up to temp and make sure heater is turned on..

If #1 isn't it (which I think it is since it's most likely):#2. There is a baffel that is moved by the vacuum system which allows the air to blow threw the heater core area or not. Perhaps this isn't working?When you move the lever from cold to hot does anything happen (noise, etc?)Or is the air like the same temp no matter what side it's on?

#3. Did you buy the car used? Perhaps they did a heater core bypass on it?

I am not too familiar with this heater core bypass you speak of but there are lines going to and coming from the heater core. I will try to bleed the cooling system with the car on jackstands tomorrow and report back... There are no odd noises when moving the temp selector from hot to cold. The heat works fine if I have 1 or 2 selected. 3 and 4 are the bad ones... The air is warmer when the slider is towards hot but it's definitely not warming my car up like it should. I am thinking it is probably an air pocket in my cooling system because the heat definitely gets warmer when I rev the engine. I know that is a symptom of an air pocket. Like I said I'll bleed the system tomorrow and report back.

[the converted]

If your getting heat at all your heater core is not bypassed. If I were you I would back flush the heater core and see if there is any crap in there. Other than that I think it's just a mater of only being able to get a certain amount of heat out of the heater core and if it's really cold out like it has been, it's going to be harder.

[g35paul]

i have this problem but mine is i either have heat or not.... after reading this im thinking i have air in mine since i do have a hole in the top of my coolant reserve tank

[elwesso]

If your getting heat at all your heater core is not bypassed. If I were you I would back flush the heater core and see if there is any crap in there. Other than that I think it's just a mater of only being able to get a certain amount of heat out of the heater core and if it's really cold out like it has been, it's going to be harder.

that would be my first inclination. Or like one of the posters above said you could have a blend door thats not opening all the way..

Buddy of mine was getting no heat at all. We took the heater hoses off and rinsed it out really good with a garden hose, then bled the cooling system and he had boiling heat... Id try that, its pretty simple!

[del82]

A few things..

#2. There is a baffel that is moved by the vacuum system which allows the air to blow threw the heater core area or not. Perhaps this isn't working?When you move the lever from cold to hot does anything happen (noise, etc?)

This is most likely. Most likely caused by a vacuum leak in the line that feeds the door actuator. This is pretty common with older vehicles with vacuum controlled HVACs. Easiest way to check is like he says in the quote, and also get up to speed on the highway and then just hold your speed, see if your heat comes back. While traveling at a decent pace, usually 40+, you're low on throttle and comparatively high RPMs, which generates high vacuum in the engine. Helps sniff out problems like this.

[nyc240sx]

my heat on my 95 240sx it only works on 4 setting when i had the ka and now with my rb25 its still the same

[the converted]

The resistors in your fan switch are shot. Get a new one and you should be all set.

[nyc240sx]

you mean get new resistors or get the entire hvac switch

[Schrute Farms]

I believe I have fixed this problem... I pulled the heater core lines and shortened them so they are no longer kinked, bled the system (for like 35 minutes lol) and voila... The heat works a LOT better (although 4 was still a little chilly for my taste but it is definitely better than what it was) I think since the lines were kinked, it caused the flow to the heater core to be restricted ever so slightly and when I had the heat on it would cool the coolant in the core too fast for new, hot coolant to get in there... If that makes any sense.