Goomz

iTrader: (1)

hey org. long time since my last post, im having an issue with my hvac. tried the search but my situation isnt here. 98 max.

i have no heat, only at 85 in my auto climate control. and its HOT at 85 only. 84-65 it blows the same temp (cold/cool air, no change in temp). i also noticed my climate control doesnt change as it used to (turn the temp up around 74-76, it would automatically switch from top vents to feet) it just stays at the top. and when i turn the TEMP down 1 degree to 84, theres a weakened output from the blower, almost as if theres a load on that circuit for maybe half a second. sort of like that real quick delay you feel when you activate the a/c. my a/c btw has been disconnected for years.

my top heater core hose broke off from the water pipe on the firewall. idk how long i was driving like this. it wasnt until i noticed my car temp climb. (nebver reached the H) i was able to slide it back on luckily without replacing the cracked water pipe. i refilled the rad. this was maybe a week ago, ive looked at it daily, multiple times a day. cardboard under the car overnight, no leaks. yesterday, i noticed my car begin to climb in temp on the highway...it was maybe 75 out and i was cruising at 70 mph at night. never went close to the H, but it was slightly over the middle. enough to notice. and it did seem to bounce down to normal eventually. cooling fans were on. today i checked, coolant level was normal, i had max level in my resevoir as well. i re bled it today, the lower hose was COLD after 60 mins of running and the fans turning on. i was squeezing it and only at certain times, no fluid fluctuation at the rad. other times id squeeze it and it would sort of overflow out from me squeezing. all other hoses (both heater core and upper rad) were hot, like normal.

i gave up, put the cap back on, went inside. 30 mins later i wanted to check again, i grabbed the lower rad hose and it was hot. as hot as the other hoses. im a little confused on this. i replaced the rad, rad fans, ects for the fans, thermostat (60 days ago). i had 0 issues until i noticed the heater core hose broke off. anyone have this idea? its really strange that the temp going from 85-84 sort of puts a load on the blower output for that half a second.

my amb button said ext 85 deg, interior 90 and intake 105

DennisMik

iTrader: (2)

I wonder if the cabin temperature sensor is not working. Is the little grille to the right of the fans switch open and not blocked?

Run the self diagnostic that will check all the sensors and whatever. It starts on page 70 of the HA section of the 1998 FSM. Read this before doing it.

Link the FSM section HA

If you have any errors, see page 68 for page numbers on specific problems.

Goomz

iTrader: (1)

yes the grille is no blocked/clogged, i will keep you posted when i run the diag, thanks for the reply

dwapenyi

iTrader: (3)

Has the center console been removed/worked on recently? Reason I ask is because that grille the DennisMik is talking about is connected to a tube. If the tube somehow dis-connected, whatever interior temps the auto climate control thinks its reading might be something else.

Goomz

iTrader: (1)

hey dwapenyi, i know exactly what little tube your referring to, thats plugged in and well.

the results are in! i got 0 issues all the way across the board. everything i did gave me the "ok" codes.
my ambient temp read 86 (about accurate), in cabin read 105 (about accurate), and intake sensor read 95 with the car on for the first time today, running for about 5 mins.

the next thing it said is "troubleshooting no heat", it said check the coolant level (full), hoses for kinks (checked that), rad cap and air in system.

yesterday i was in about 100 degree weather in rush hour stop and go for about 45 mins, the temp gauge didnt go to the h, but maybe 1/8 way over the middle, and when it was in normal op temp, it was maybe 1/8 under the middle. it never went above those marks, and did eventually drop back down when i hit highway speeds. im going to assume theres still an air bubble still in the system.

in my op i said all was well before the line fell off the water hose, so i am going to disregard the "check rad cap." if it helps, one time i blasted the (lack of) heat, and it stunk in the vents like coolant with no heat. still no leaks around the heater core hoses around the firewall, or interior.

DennisMik

iTrader: (2)

If the engine was full of coolant, the temperature gauge should stay in one spot, a little below the mid point.

To check for air in the cooling system, start with a cold/cool engine. Raise the front end of the car up maybe 12 inches. Remove the radiator cap and start the engine. Let the engine run until it heats up and the thermostat opens, allowing the coolant to circulate through the radiator. If there is air in the engine, it will escape at this time.

But be careful. Sometimes the air bubbles come out causing a spray, so don't be looking into the radiator. Run the engine for maybe 5 minutes once the coolant starts to circulate.

While you are doing this, the radiator fans should start running. Check and see if both your radiator fans are working.

dwapenyi

iTrader: (3)

I wonder if maybe the valve that allows coolant to flow into the heater core is sticking. It only responds to when forced to move, as in the maximum heat position. Maybe a little lubrication on the valve will free up its movement?

DennisMik

iTrader: (2)

I have to disagree with you because there is no water valve for the heater core. Water flows through the heater core all the time. The 1994 3rd gen was the last year to have a valve.

Nissan replaced the water valve with the air mix door in the air duct system. If heat is needed, the air mix door allows air to flow through the heater core, otherwise the air is diverted around the heater core.

Goomz

iTrader: (1)

Hey so I rebled the car as stated and let it run w the car on a slight hill and jacked up. Both of the fans turned on and I ran the car for 10mins more. The lower hose was cool to the touch still, until a few mins after I turned the car off and recapped the rad. Then it got hot. I'm thinking defective thermostat? I got mine at autozone. The temp read even lower on the gauge, maybe a little more than 1/8 under the middle. Still the same issue w the heat only on at 85, and the vent mode still doesn't automatically switchover as I turn the heat up on the dial.

DennisMik

iTrader: (2)

The thermostat is not opening up like it should. Replace it with one from Nissan. So many people have problems with aftermarket thermostats and you have joined the club.

I am somewhat confused with the vents. I don't think the mode changes when you change the temperature. You ran the diagnostic and it not uncover any errors. So either I am misunderstanding what you are saying or you are expecting the car to do something that it is not designed to do.

dwapenyi

iTrader: (3)

Yes OEM thermostat. That autozone one isn't broken, it just sucks!

Also remember that the auto climiate control is smart and won't change modes until it knows that the temps are warm enough. Think about when you first start your car with a cold engine. With the auto climate control on auto and temps at 85, the fan refuses to engage until temps have risen.

Goomz

iTrader: (1)

Thanks I'm going to get one from the dealer. And yeah I always noticed (cuz it annoyed the hell out of me) that when I went to turn the temp up on the display, when it reaches around 75 degrees, the mode switches to the lower vents/feet. And when I turn itback down, it goes back to the top vents automatically. But I am def going to replace the thermostat w OEM...I'll keep u posted

dwapenyi

iTrader: (3)

The auto climate control has a full manual mode too. You can make it everything the manual climate control does.

Push the off button, then push mode and voila. Keep pushing mode changes where the airflow goes.....feet.....vent .....etc.