geedub3

Hello fellow 240SX'ers,
I'm brand new to this forum....but I feel it's the best place to get some helpful "help me out" tips.....

I have a 1991 240SX and although I live in the Phoenix, AZ area the weather has been fairly below average lately and the winter nites are always pretty brisk.....Anyway, my heater is not working at all. It only blows out cool air. I've tried cycling the tempature control **** (the slider thing) and nothing happens but the cool air. Now last winter when I had to use my heater it was working fine. I've had this problem now for a little over a month when I tried using the heater for the first time.

Does anyone have any suggestion to what could be the problem? And how to correct it.

Your suggestions would be greatly appreciated.

GW

kang128

hey i'm pretty new to the 240 forums too and i also have a 91 with the same problem. i'm gonna bring it to the shop this weekend and let my friend there take a look at it. Ill give you an update when i figure out whats going on

wikd240

the first thing you have to check is if there is antifreeze in the radiator... might sound dumb to some people but thats the first thing to check... if the radiator is full then you need to find out if your heater core is plugged or obstructed by rust or other build up...
the way to do that is... drain the cooling system... remove the upper and lower heater hosees and blow air through the pipes going into the fire wall... now when you blow air thrugh the tubes it should come out as fast as you blow it in... if there is little to no air comming out then you have a blocked heater core...
if the heater core is plugged then you are going to have to replace it which means the dash come off so you can get at the heater box...
i have never done this to a nissan but i have done it lots of times...
the best suggestion i have for you when doing this if you do it yourself is to lable every plug you unplug with tape on both sides with a matching number... that way you make sure that the right plugs go to the right place...

TWAN

Or just look under the dash where the heater box is and find the cable that opens and closes the coolant baffle. Once you see it which its not hard to spot make sure its connected and actually moving the baffle. Probably your simplest troubleshooting option. If it is moving it try what wikd240 said to do. I have had them come unhooked or broke off the arm on the baffle.

geedub3

Kang128, Wikd240 and TWAN,

Thanks for the suggestions.

Kang128...Thanks, let me know what he finds out..

TWAN...I'll try your suggestion first. But (since I know about my engine better than some of the interior workings) where is or what side under the dash is the heater box where the cable that opens and closes the coolant baffle located? (driver side, passenger side?).

Wikd240...I'll try your suggestion if TWAN's suggestion isn't the solution.

Thanks all

GW

TWAN

Passanger side behind the glove box. If you cant find it take your radio out and you will see the cable which looks like a yellowish white tube connected to the bottom of the climate control unit. Follow it to the bottom of the black box which is your blower box. You should be able to do this without taking anything apart. You just might be cramped a little bit.

geedub3

TWAN....thanks, we'll take a look this weekend

GW

l2aine

Correction - the heater core unit is not behind the glovebox, but behind the center of the dashboard itself (the a/c cooling unit and HVAC fan is behind the glovebox).

First make sure you've got coolant running through both heater core hoses. You can do so by turning the heater 'on' and running the car for a bit until the coolant is warm. Before it gets too hot, check the heater hoses by feeling their temperature, they shoulbe both warm. If one hose is cooler than the other, then check the watercock if it's open (you can open it manually if it's closed). If the watercock is open and only one heater hose is warm/hot, then for sure one of your problems is a blocked heater core.

If the interior controls are set to full hot, and yet the watercock is still in a closed state, then you might hve a problem with the airmix door motor, which also controls the watercock. This motor is located on the heater unit, which is behind the dash - so you'll have to pul the dash anyways to make sure.

TWAN

Sorry about that. Im very aware of where it is. But i was just giving him the easiest way to find it without removing the dash.

l2aine

No apologies man, it's cool

I'd like to emphasize the airmix door, since it's been a more common problem to other 240 people I've talked to, moreso than the heater core.

geedub3

l2aine and TWAN thanks for the suggestions. Didn't get a chance to take a look this past weekend (had a busy weekend with the kids and family). Will do the recommended suggestions this weekend. Will keep you posted on what I find.

GW

vbgambini

my heater isnt working either, it just blows out cold air too.....is it expensive to fix or is it just a bolt on sorta thing?

l2aine

If it's the heater core, you'll have to pull the dash and some of the other HVAC parts to access the core, as it is positioned behind the radio cage and is attached to basically everything that has to do with the HVAC system - it's the last part of the path of air coming from the fan before it hits the main airduct system that channels air to the appropriate vents.

First check the easier heater components before you go for the heater core. Check the temps of both heater hoses, check the airmix door, check the watercock.