q a/c not working properly.

[1991q45]

okay. when i found out the condenser was no good i plugged lines to prevent moister and particles from getting in the system.
got a brand new condenser off of ebay, installed it.
i put pag oil in too.
the car took 4 cans of r134 before it got cold.

now i have a problem.
the a/c starts out cold but after a minute or two it gets cool.
i looked thru the site glass and on start up it looks full but the longer it runs the more the refrigerant looks like it's emptying out.

now i noticed the high port (where the hose connects into the receiver or bottle) it's cold.
the low side port (line leaving the compressor)it's kinda warm.

i felt at the evap. lines the top part felt warm while the bottom felt cool.

now my mom is pissed and wants to get rid of the car because of this issues...i disagree.

help me out guys...any suggestions?

[Infinitiguy19]

Some would say your mom is right if you don't have the money or knowledge to fix the Q if in real bad shape.

Sorry I can't help other than to point you the service manual because I know nothing or HVAC (A/C) systems on a automobile: http://www.nicoclub.com/FSM/

[qship96]

The a/c system DEMANDS perfection to operate as designed........a moisture free leakproof system filled to EXACT weight of refrigerant and lubricating oil.........take to a professional and have system evacuated, vacuumed,leak tested{and any leaks repaired} and refilled with the EXACT weight of refrigerant......if it does not work correctly at this point, the experienced tech will diagnose and replace any defective component needed. Just adding a bottle of refrigerant or 2 in the driveway is a surefire way to complicate diagnosing the entire system.

[Q451990]

Has your system been converted to 134a at some point? The 1991 came with R12 from the factory...

Heath

[1991q45]

yes it has. i even checked the fittings to see if they're leaking.
qship96 let me tell you a story:
i had a 93 nissan maxima with the vg30e motor.
the person before smashed the front end only replacing the radiator and fan.
it was like this for a year.
i bought the car got a condenser and filled it with r134.

i did it the wrong way on so many levels and to this day the a/c works perfect on the car.

the q i did right. made sure it was lubed properly and first.
i bought the part new.
but if it's leaking i'm kinda willing to bet it maybe the compressor.
i will take a look into the service manual.
i feel like going out there right now and seeing if the levels the same or what.
i'll keep you guys posted.

thanks for the input.

[Q45tech]

The 30 minute vacuum proceedure [plus replacement of receiver dryer dessicant] is important to remove the moisture in the system from opening to atmosphere BECAUSE the moisture freezes after a short while. The ice crystals jam up everything and can destroy the compressor in a short time!!!

Letting things go and go just builds up the required repair cost. History on hundreds of Q has shown that $2,000 per year [each and every year] is the minimum

[1991q45]

so correct me if i'm wrong.

so the fact that the hi side is very cold. it developed ice crystals which jammed up the compressor? destroying the compressor?

today i took a look at it this morning it was still full.
but this time no cold air.
and the compressor was engaging on and off quickly. it'll engage for a second then stay disengaged for a few seconds.

so i over rode the switch and the compressor came on.
and when it engaged the engine literally slowed down...this did'nt happen yesterday.

i hooked the line up to the low side it was the same but when it was off. it rose all the way in the red. don't remember the reading but thats what happened.

now i know the maxima and q are two DIFFERENT car's. but i figured maybe i can get an idea on whats going on.

the low side where it leaves the compressor into the evaporator was cool.
everywhere else was hot.

i'm leaning towards the compressor though. and you do have me thinking about the decessant bag.

whould a bad dryer cause this?

[Infinitiguy19]

Did you look at the service manual at least to perform a self diagnostic via the HVAC control unit?

[mikes94q]

from my experience if the compressor is turning on and off quickly it does not have the required amount of refrigerant, or to much. Best thing would be as q45tech pointed out. I have a vacuum pump and gauges that I got from harbor freight Suck everything out and keep going for like 30min to remove any moisture. Then use the proper manifold gauges to replace the refrigerant. Depending on your altitude when you vacuum everything out you will have a negative psi reading that you want the car to maintain for 20-30min prior to putting in the refrigerant to ensure that there are no leaks.

[qship96]

so correct me if i'm wrong.

so the fact that the hi side is very cold. it developed ice crystals which jammed up the compressor? destroying the compressor?

today i took a look at it this morning it was still full.
but this time no cold air.
and the compressor was engaging on and off quickly. it'll engage for a second then stay disengaged for a few seconds.

so i over rode the switch and the compressor came on.
and when it engaged the engine literally slowed down...this did'nt happen yesterday.

i hooked the line up to the low side it was the same but when it was off. it rose all the way in the red. don't remember the reading but thats what happened.

now i know the maxima and q are two DIFFERENT car's. but i figured maybe i can get an idea on whats going on.

the low side where it leaves the compressor into the evaporator was cool.
everywhere else was hot.

i'm leaning towards the compressor though. and you do have me thinking about the decessant bag.

whould a bad dryer cause this?

Without evacuating and refilling TO EXACT WEIGHT with refrigerant EVERYTHING IS A GUESS......once you accept this simple fact and do so, everything becomes easier to diagnose.

[elwesso]

you really need a manifold gauge set to determine whats going on for sure...

http://www.nicoclub.com/FSM/Q45/1994_Q45/ha.pdf

start on page HA-33 and see which one seems to most closely match it... its at least a start. The dryer (liquid tank) could be clogged, which is why any time you open the system to replace a component you should replace it...

[1991q45]

i plan on renting a set at my job.
but i read the fsm.
and there was one where it said the liquid tank inlet and outlet has a big temperature difference. the outlet side temp. is very low. But the other side is kinda warm.
the hose that leaves the condenser into the compressor is hot as hell!!

well assuming the outlet is the one that leaves the tank and goes into the evaporator, your right. it seems the liquid tank is clogged.

which seems to make sense; when i shut off the car for a few minutes, then cut it back on, it only works for a couple of minutes.
which also explains why the sight glass would start out "filled" but ended up looking empty.

and the on/off of my compressor.

y'all agree??

[elwesso]

sounds reasonable, especially considering you mentioned nothing of the dryer being replaced... which you should definitely do...

[Q451990]

FYI this guy is a great seller... I bought a couple to have as spares.

http://cgi.ebay.com/ebaymotors/NEW-OEM- ... ccessories

Heath

[1991q45]

thanks!! also you don't think the expansion valve has been damaged do you?

[Q451990]

If I had to guess, I would say the fact that it works for a little while is a good sign, but I really don't know...

Heath

[1991q45]

ok, a buddy of mine and me are supposed to check it out with the gauges tomorrow but i kinda think it's a waste now.

thanks to you for helping me out.

one more thing though, i was concerned if the clog was somewhere else.
but i found my old lti book...and it basically gave me the po' man way's of checking my a/c out if i didn't have the equipment.

had the a/c on again freon was still the same. felt across the lines. the only part that seemed to change besides the receiver was the condenser.

so i don't want it to affect the new receiver...how would i get the system cleaned out? this is where the vacuum pump would come in handy?

[Q451990]

If it's just water freezing, then you'll loose it when you pull your vacuum after you install the new dryer. So - recover refrigerant, install new dryer, vacuum. If it's actually debris, you can buy a cooling system flush at a parts store. It seems like a very very light mineral oil when I used it. I tried pouring it in and then flushing it out with compressed air when I replaced the evaporator on my old truck... seemed to work OK, but I'm sure there's a better method.

Heath

[Q451990]

A little more advice. Don't remove the plugs in the dryer until you're ready to install it. It's shipped under a vacuum and should stay that way until it's installed - then a vacuum should be pulled on the system as soon as possible.

Heath

[Q45tech]

Over 20 years I've gone thru 3 compressors and replaced the dryers about 5 times [they are cheap compared to other components]. If changing a dryer were to extend compressor like by only 1 year it would be cheap to do it every 2 years.
Flex hoses have a finite life as do condensers and evaporator assembly.

All my preventative measure has allowed me to still run as built evap and expansion valve. Removed and cleaned once then foamed in place periodically .

The question is how many minutes and seconds of cooling reserve you want when virtually stopped in bumper to bumper traffic when the road air [exhaust supplemented] exceeds 110F.

Those that wear suit and tie have more rigorous standards of what cool is.

[1991q45]

thats what a couple journey tech's told me. i gotta have the system vacuumed out.
so i ordered the receiver from my job and have one of the shops we do business with do the job.

he told me if i get the refrigerant and of course i'm gonna get some more pag oil. he said he's gonna run it through the machine for at least an hour.
all for $30. and yes i'm gonna be watching the whole time.

and i'm happy to report there are no leaks!! to this day it still turns on (my mom turns it on hoping it'll work)

[Q451990]

$30 is an awesome price if he knows what he's doing - even if he only sort of knows what he's doing! You should buy him a couple of cases of beer for hooking you up with that deal.

Heath

[qship96]

thats what a couple journey tech's told me. i gotta have the system vacuumed out.
so i ordered the receiver from my job and have one of the shops we do business with do the job.

he told me if i get the refrigerant and of course i'm gonna get some more pag oil. he said he's gonna run it through the machine for at least an hour.
all for $30. and yes i'm gonna be watching the whole time.

and i'm happy to report there are no leaks!! to this day it still turns on (my mom turns it on hoping it'll work)

Seems strange a shop does not have their own r134a ????????

[Q45tech]

I devote about 2 hours of personal time PER YEAR to AC cleaning and mainteance.
Remove the fan [or darlington speed controller] and foam clean evaporator, vacuum down, weigh, add oil [removed by vacuuming ~ <1ounce] recarge from my oil R12 and add any that has leaked thru hoses or orings - usually minor maybe 100 grams [<1/4 pound]. USE compressed air to clean fins on condenser and rad.
Check condenser fan motor for single or multiple speeds [depending on year].

Keeping everything spot on means the system acts spot on and the compressors last > 6 years

[dsagers]

Q45tech, how do you determine the amount of oil to add in for leakage? I understand adding an oz for what is pulled by the vacuum, is there a way to measure the oil in the system, or a method to tell how much oil to add?

[Q45tech]

Not easily but vacuuming my system down 20+ times and ocassionally draining old compressors after a replacement get you clarivoyant on your particular vehicle after 20 years.

The UV dye and signs of leakage plus you can tell when you've added too much if you are sensitive.

They make a screw jack crank device that allows oil to be added when system is pressurized thru the test ports.

eventually with a stethoscope on compressor you can hear when the amount of oil is just right +- 1 ounce.

[dsagers]

Ah yes, the finesse of an artist, highly experienced mechanic!

If I'm within +- 1 ounce, will the system be OK?

[Q45tech]

The efficieny is bell [gaussian] shaped like IQ +- 1 ounce [12% range] doesn't seem to affect the temperature.

I used to flush the system out of oil with a special hydrocarbon then weight it but no longer easily or cost effectively available..

The scale within a $8,000 AC machine is accurate to within 0.01Kg so 10 grams/28 = 0.34 ounces.


I'm not a MECHANIC as that term is a gross insult to an educated person. Kind of like calling me an MFing SOB.

[dsagers]

I'm not a MECHANIC as that term is a gross insult to an educated person. Kind of like calling me an MFing SOB.

Agreed, your writing shows you are very well educated in automotive science and engineering, however, no offense meant.

What professional title do you prefer?

[1991q45]

oh he knows what he is doing.
i think he was gonna charge me an extra $50 for r134.
but he told me if i wanted to save some money i can buy it from my job.
but the reason the price is low is because we do business with him.

thanks guys for all of your input.
i wanna keep this car on the road and in my possession for as long as possible (shh don't tell the maxima i said that, lol).