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Maxima AC will suddenly not start


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terminalVoltage
Novice

Jul 13, 2016, 1:40 PM

Post #1 of 8 (550 views)
post icon Maxima AC will suddenly not start Sign In

I have a 1999 Nissan Maxima with 235,023 miles with a manual temperature control module that is having an issue with the air conditioning. It has had problems since I got it, in the past it would not turn on because the aux radiator fan would not spin, but if I spun the fan with my hand it could maintain its self running and the low line would cool down, since then I have replaced the radiator fans and the AC worked great for the 2 days before this morning. This morning I got into it and I got nothing but hot air. The fans are both turning on high speed if i turn on the AC and the compressor also sounds like it is turning on, and my RPMs go up by 500 RPMs but the low side will not cool down. I replaced the fan two days ago it worked for two days but today I am getting nothing, I haven't checked my freon yet but I did just before replacing the fans, so I assume that isn't the problem. The car has a new climate control head and I know for a fact that the air mixture door is on full cold. The air conditioner also has a brand new relay. Does any one have any further diagnostics or replacements I could make? Also it looks like just before I received the car that the condenser had been replaced as all of the fins are pristine and perfect and doesn't look like it was the original one from 1999.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jul 13, 2016, 2:02 PM

Post #2 of 8 (545 views)
Re: Maxima AC will suddenly not start Sign In

Don't touch anything with refrigerant just yet. Look at hub of compressor to see if it's engaged or not when it does this.
Just that for now and let's go from there. Just feeling return line is a clue but will be different normally depending on how low it's been running and how hard it's working or not so conclusive without all factors into consideration first,


T



(This post was edited by Tom Greenleaf on Jul 13, 2016, 2:03 PM)


terminalVoltage
Novice

Jul 13, 2016, 2:11 PM

Post #3 of 8 (542 views)
Re: Maxima AC will suddenly not start Sign In

Yes, not only can you hear it but you can also see it engage.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jul 13, 2016, 2:24 PM

Post #4 of 8 (532 views)
Re: Maxima AC will suddenly not start Sign In

OK - Take high and low pressure while engaged and fans working at a raised RPM a bit. Note temperature of air coming in thru grille and that fans are in fact blowing the proper direction.


If so report the pressures you observe and the temperature. Give it a few minutes to get a credible reading - both pressures or no point IMO,


T



terminalVoltage
Novice

Jul 13, 2016, 2:33 PM

Post #5 of 8 (528 views)
Re: Maxima AC will suddenly not start Sign In

Whats the best way to take the temperature from the grille? My grandpa is a retired mechanic who has a AC manifold set but he is too busy to help me very often, I will ask him to take the pressure readings tonight.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jul 13, 2016, 2:59 PM

Post #6 of 8 (523 views)
Re: Maxima AC will suddenly not start Sign In

You can make a good guess but when or if you touch the refrigerant you really need to know actual conditions or when everything rules out have it recovered and recharge by exact listed weight of refrigerant or you don't have a good baseline to work with if that doesn't work perfectly.


This is with no tests that show a leak which can happen at anytime or even if thought correct no heater getting mixed in with the vent temps. You could just pinch off the inlet line for test at the risk of wrecking the heater hose.


You just have to rule out all silly (some not silly) problems first like I asked if the fans were blowing towards the engine or backwards - it happens if new usually with some mistake.


Pressures and all observations first, even if hub of compressor is slipping and can but would wear out in no time if so,


T



terminalVoltage
Novice

Jul 13, 2016, 3:10 PM

Post #7 of 8 (521 views)
Re: Maxima AC will suddenly not start Sign In

I know for a fact that the AC and heater are not getting mixed, the door is over as far as possible. And the fans are blowing towards the engine as they should be. By the air going through the grille do you mean the ambient temperature outside? Also couldn't I just touch the low side to see if it is cooling as it should be?


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jul 13, 2016, 10:21 PM

Post #8 of 8 (506 views)
Re: Maxima AC will suddenly not start Sign In

Ambient temp is what the condenser sees as the temperature. Reason I say that is the air over a hot surface could be lots higher than the day's forecast. Everything is so temperature pressure related you can easily be fooled.


Just a nice chart - shows that if you know the temperature you know the pressure and vs verse. Just a cool return line where you check is a clue on some or could mislead you - even pressures still a must for diagnosis if a compressor is engaged and "pumping" what is happening. They really don't tell you how much refrigerant is in the system rather that it's in line with the temps it's dealing with.


Chart>

It's handy to know this. Infrared, touchless thermos can help a lot, the meat thermos are useful and I like now hard to find wired in/out thermometer like for a window sill and hang a wire outside not the wireless ones that are a bit slow.


*******************************
Most systems the evaporator right where liquid refrigerant evaporates will go cool to the touch (or see its temp) and stay close to that temp thru evaporation and right at exit be about the same temp. If way off it exhausted the sweet spot of any evaporation staying as close to constant thru it - frequently a low charge but not always is the real problem.


It's always a book of know how and observations to know its even right when nothing is wrong and a longer book to know you need to fix something not always mess with the refrigerant is the huge mistake.


I question with this erratic if it's either not compressing gas properly, mixing with heater core heat still if all was brand new doesn't prove anything for sure then the end all is knowing the "weight of the charge" is correct. You can't know that without removing the existing charge either weighed coming out if it WAS correct then adding the specified charge to the ounce if possible.


Systems are not tolerant of being just "close enough" but really want the right charge known at some point.


Pressures lead you to the clues of what's going on along with temps it's dealing with and again temp at a center vent inside of what the system is actually doing.


You have none of that info so we are stuck.


You can rent gauges. You can buy the thermometers not all that costly. Should own a test light or DVOM (volt/ohm meter) just useful to own if you do any assorted work on cars and other things too.


To really get serious with A/C and charging you need to own the equipment or access to it. It's prohibitively costly to own enough for a lot of folks wouldn't ever pay off. Mega thousand$ of bucks.


Chances are you do have a leak no matter what parts look like - condenser can catch a stone on your first drive home with a new car - rule out nothing as possible for leaks.


Right now we need some info - is it compressing gas at all? You said it turns on/engages but is it doing anything and if so what?


I've mentioned some things that are possible but this will just be another 2 year vocational program in learning principles of A/C then applying that knowledge to the problems you encounter with the equipment. So far we have none.


What do you want to do?


If you are very handy there are things you can do but at least know what while any refrigerant is in the system and right now don't even know that.


Pay to have it diagnosed is a bargain then decide if you can take it on or not.


Just don't touch refrigerant charge especially with the single gauge cans sold all over the place in the trade called Death Kits as they are not good product, accurate nor enough info just like feeling that return line as you said it will probably say you are overcharged and you can't know that so well right now.


The problem with many things and A/C work if wrong is the wrong moves cost a fortune and set you back worse off than not touching it at all too many times,


T







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