'94 Maxima with barely any interior heat
 

My fiance has a '94 Maxima (SOHC V6) which I bought for her last year. The car works great, is in excellent condition, but has barely any interior heat. It is the model with the climate control system, and we have it turned up all the way. The engine temp is great so I'm kinda stumped. We live in Nova Scotia, Canada and sometimes the temp outside gets down to -25C (-13F) so it would be nice for her to be warm on her drive to work in the mornings. Any help you guys could give would be huge, thanks

Thermostat. My 94 was luke-warm here in Oklahoma last fall. Put in new thermostat, it's roasting now. In fact, defroster cracked the windshield on the first snow :(. I was just reaching to turn it down and POW!

Check the vacuum lines on the heater valve. If one falls off, there will be pretty much no heat (maybe a little that manages to get by)
http://i242.photobucket.com/albums/f...281602_070.jpg

heater core might be plugged, take the inlet/outlet hoses off of the firewall and spray some pressurized water in, you'll see milky water come out the other side with bits of junk in it. did that to my truck and now you can roast at turkey over the heat vents. possibility it might be too plugged to save though

otherwise thermostat is a cheap/easy place to start

Tell her to deal with it.

This doesn't help

The thermostat idea is probably going to be my first place to look, ours also only has that mildly luke warm air

how the dash temp gauge reading?
make sure the fresh air vent lever on the left of the controls is closed(down iirc)
and there is a recirculation vs intake fresh air as well

not sure if the digital climat control has these functions tho

The dash temp gauge is reading normal, about half. The climate control model has the fresh air vent, which is closed, and I've tried both recirculation and fresh air but neither seem to make much of a difference.

is this something that happened all of the sudden or it was a gradual loss?

It has been like this the both winters that we had it, just probably didn't notice it as bad last year since it was a much more mild winter

sounds like a plugged up heater core. try flushing that out.

there's also a heater valve that's attached to the firewall also..make sure the vac line on that thing is good and clean.

Breakdown of what you should look at first. Get engine up to operating temp. Have someone in car turn climate control on while you observe whether the heater valve on the fire wall moves. If it does not move or move only slightly, you need to check vacuum lines. If those are fine, come back and we can help from there.

If the valve is working, then do check the fresh air vent. I completely forgot about that stupid thing! The operation to open/close it is mechanical and the line can sometimes come loose. It should be a blue or aqua green cable. It does not come detached from the door, rather the small metal bracket that holds the cable sheeth on the air box behind the glove box comes off. This subsequently prevents the cable from opening and closing the vent door. It's like your throttle cable, the sheeth has to be secured for the cable to do its job. As part of this process, you can also determine whether the climate control is even trying to open or shut the door (again trying to rule out a bad climate control while looking at other areas). You're going to need to remove your glove box to make things easier.
If all that checks out, then I would suggest pulling you fan control switch (located in duct beside fan, unplug and unscrew). This allows you to access the inside of the duct and inspect for debri and obstruction of the coils. You can clean it off with a water hose if clogged.
If clean, then move to tougher stuff like flushing the heater coolant. Then do the thermostat. But I'm betting its not the thermostat because you say temp guage sits properly when warm. i think if the thermostat was bad, you would see either long warm up period or never getting warm OR initial heat from heater and then loss of heat along with clear drop on temp guage.
I actaully think it would be more likely at that point to be the water pump. I've seen the VG with a bad/failing pump to cool the engine properly, but in winter fail to provide enough circulation pressure to force coolant through the heater core. Of course if you do the water pump, should also do thermostat regardless.

Just my .02 cents about the path to take. I just don't see logic in jumping into the big stuff if little things are still uncertain. I'd hate to think you would change water pump or flush heater if it was indeed that stupid bracket/clip fell off the vent door cable!

Ok, this is really helpful. I have checked some things already, the heater valve is working properly, and the fresh air vent is opening and closing as it should as well. The water pump was replaced last year, but the thermostat wasn't. It does seem to take a long time to warm up, I had the car running for 10mins this morning before the engine temp started to rise at all (where on my winter-beater Tempo it's pushing hot air after only a min or so)

My gauge read normal too. Just insufficient heat in the passenger compartment. The thermostats job is to get everything up to operating temperature quickly. Cooling is the radiators responsibility.

So you're thinking for sure it's thermostat? I priced them today at local auto parts shops, they range from $40-$46 or more, a lil pricey for a thermostat...but then again everything I'v e had to buy for this car to date has been in the higher price range

Probably one of the most expensive thermostats I have ever purchased for an automobile in the 40+ years I have been working on them. My '94, I had done all the maintenance on the vehicle for the original owner. He bought a 2010 Camry and sold me his Maxima. He nor me ever put a thermostat in, meaning the Original Equipment stat was changed in 2011. 17 years... I think we got our money out of it. :)
While the others have some valid points about other things to check. The age of the car and not knowing past repair history, I'd put a stat in it. Then while the cooling system is drained one can disconnect the heater hoses and flush the core. I have a short piece of 5/8" hose with a 3/4" female garden hose fitting in one end for attaching to a garden hose, other end attaches to heater core tube. Flush through both tubes, inlet and outlet, one at a time.

As for climate control temperature control, fastest way to check it is to listen for the change in airflow while moving the control from full hot to full cold. As the air changes from moving through the heater core to the evaporator core there will be a change in flow\sound. That tells one the door is moving.

oh dont the digi climate models actually have a ambient cabin temp sensor in the stereo plate? just to the left of the stereo ,might be unplugged,dirty,bad or missing from like a radio theft or swap,all my non digi cars had a empty spot ,with the slits and i usaully mount my alarm leds there

on the 4 3rd gen maximas ive owned in the last 12 years the Only problems with the climate system was my white 92 gxe-no a\c and the temp slider was worn so i swapped the base,
also the gxe had the heater valve vacum leak and the fresh vent was not connected behind the lever and i put a new cable in,but the other 3 had bangin heat son and a\c working ,anyone who read the owners manual and can appreciate the max defrost setting since it uses the a\c which in turn coincidently acts as a bit of traction control since it takes hp to run and is usually on when icy and rainy

so in my experience 3 outta 4 having near perfect heating and a\c systems aint bad
ive also had very good luck with not needing to swap window regs.injectors,fuel pumps,motors or gearboxes...oh and non of my nissans have ever failed emissions or hurt anyone,lol

Hi Chris...I have a 89 Maxima and the 2 vacuuum lines are disconnected on the water control valve...Could you please tell me where to hook them up...I have heat at the strangest times...never when i need it....thank you, Jeff

Be careful if mess with the heater hoses. The plastic ends of the heater core that come through the firewall are brittle. I broke the end of one of mine, I was barely able to get the hose back on. Because of this I will never drive out of town in my Maxima.

The Fresh vent lever(on left side of climate controls) if your moving the lever up and down (open and close)
And your Not hearing the noise of the flap door closing (listen under glove box) your cable has broken from the back of lever(small thin plastic mount hole)
look under glove box for the brite blue plastic sheath covered metal wire cable,turn the mechanism it ends at by hand,leave it closed(its under glove box/towards middle)--EDIT ,its more like behind the ashtray or above the ecu but reachable from under/behind

EDIT ,its more like behind the ashtray or above the ecu but reachable from under/behind