# 97 altima A/C problem



## Lawless100 (Aug 9, 2007)

This is going to be long so bare with me.
I was in a accident a couple years ago which required a new condenser, and radiator and some new "plumbing".
The A/C was working great for a while but it began to leak from one of the replacement parts the body shop put it. It was a little line that goes from the reciever/dryer to the top of the condenser. 
They ended up having to replace this part 3 times before they got one that would last more than a couple of months. 
This was fine and dandy, until this year.
When I turn the A/C on it is cold as hell, almost too cold, as I drive I notice I will hear a click which sounds like the compressor, and the RPM's go up. then the air stops working. I don't feel the drag of the compressor and I have to turn off the switch for a few minute (sometimes more) and turn it back on and it is cold again.
I went through the whole system, no leaks, I took it to a VERY reputable mechanic locally. These guys know their stuff. because it is a intermittent problem they had a hard time diagnosing it. It turns out the high and low pressure switches work, and the compressor is receiving 12 volts, but it is NOT receiving a ground. This is apparently controlled by the ECM. Instead of replacing the computer they decided to install an override switch in the dash which gives the compressor the ground and everything works fine. This is great but it happens all the time. Once the compressor fails I need to flick the switch on and off every few minutes. I don't want to keep it on and burn out the clutch so I just deal with it. 
My question is, that clicking sound which I originally though was the compressor, is actually the condenser fan turning on, which is also controlled by the computer. Can't I just tap into the ground from the condenser fan and the compressor will function normally again? It's like the sensors are all working, the computer is turning everything on, but because of the bad ground between the computer and the compressor I need to turn it on and off manually. 
If I could tap into the ground for the fan this would be great


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## x60079 (Aug 20, 2007)

Wow, an ECM ground going bad. I don't hear that very often. Im not sure how much you are going to like having the compressor grounded with the fans because that will mean that whenever your engine gets warm and turns on those fans, your a/c compressor will turn on as well.
As far as this being an acceptable way to control your a/c...im not sure. your triple pressure switch has a low and high side which control the compressor. The mid range controls the fans. So how will you get system pressure into the mid range to kick on the fans if your compressor isn't running.
Also, you say that it starts off really cold and then cuts out and then you need to wait. Sounds like your evaporator core is freezing, maybe a faulty expansion valve.
Good luck!


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## spat (Oct 15, 2005)

actualy there are two fans, normaly only one is used for the cooling system but I think it can use the second if neccesary but thats rather unusual plus while driving down the highway you get plenty of airflow to not need the cooling fan most of the time. The second fan is dedicted for the a/c system. I will look into the schematic later and see if I can come up with a better solution. Sounds like a good shop he went to to get that proper diagnosis. I have seen many ECM grounds go bad and just confuse the hell out of techs. I have installed similar switched relays for fuel pump grounds in the past.


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## Lawless100 (Aug 9, 2007)

x60079 said:


> Wow, an ECM ground going bad. I don't hear that very often. Im not sure how much you are going to like having the compressor grounded with the fans because that will mean that whenever your engine gets warm and turns on those fans, your a/c compressor will turn on as well.
> As far as this being an acceptable way to control your a/c...im not sure. your triple pressure switch has a low and high side which control the compressor. The mid range controls the fans. So how will you get system pressure into the mid range to kick on the fans if your compressor isn't running.
> Also, you say that it starts off really cold and then cuts out and then you need to wait. Sounds like your evaporator core is freezing, maybe a faulty expansion valve.
> Good luck!


The expansion valve was fine, they checked everything, I thought it was the evaporator freezing also. IT turns out it's an electrical problem. The compressor is not always getting a proper ground. IS there a way to install a switch that automatically completes the ground connection when necessary? Right now, when the ground fails I need to flip the switch manually and turn it off this can go on for a while.


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## spat (Oct 15, 2005)

I need to look closely at the schematic to determin a good way to do it. I think we can come up with something but it may involve a relay and a thermo switch. I'll post back sometime today.


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## spat (Oct 15, 2005)

Darn it! Do you have manual or auto climate control? I am thinking the auto was an option not standard but I need to know before reading the schematic.


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## Lawless100 (Aug 9, 2007)

*A C Problem*

It is manual Climate control.


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## spat (Oct 15, 2005)

Ok I have got it figured out. You will find in the schematic below I have added 2 relays and a 30 degree thermo switch. The thermo switch should be mounted in the evaporator box near discharge to get in a manner it get as much direct air flow as possible. The thermo switch will turn the compressor on and off via relay one as needed to prevent freezing. The toggle switch can simply be the switch that has already been added. Relay two is just a cut out if the system pressure gets to high. You don't want to bypass that high pressure switch. This is a cheaper fix than a new ECM, however it still wont be that cheap plus locating a 30 degree thermo switch may be a little difficult as well. The relays are rather simple to find. Hope this helps. Sorry to take so long. Took a pain killer at lunch and was out cold. 








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## x60079 (Aug 20, 2007)

Spat has a great solution to your problem. The only thing that I would add to that is simply delete the 30 degree temperature sensor. The wire that he drew coming from the triple pressure switch will connect ground if pressure goes too low or too high. The low side pressure switch is what the air conditioner uses to prevent evaporator freeze up anyway. I honestly think this will be the perfect solution to your problem. Two relays should cost you less than $10 and you are set my friend! 
While we are talking about his diagram, could someone give me a good explanation of what the Thermo Control Amp does? I have never seen this device before.


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## Lawless100 (Aug 9, 2007)

Thanks guys!! I really appreciate all your help!!







x60079 said:


> Spat has a great solution to your problem. The only thing that I would add to that is simply delete the 30 degree temperature sensor. The wire that he drew coming from the triple pressure switch will connect ground if pressure goes too low or too high. The low side pressure switch is what the air conditioner uses to prevent evaporator freeze up anyway. I honestly think this will be the perfect solution to your problem. Two relays should cost you less than $10 and you are set my friend!
> While we are talking about his diagram, could someone give me a good explanation of what the Thermo Control Amp does? I have never seen this device before.


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## spat (Oct 15, 2005)

x60079 said:


> Spat has a great solution to your problem. The only thing that I would add to that is simply delete the 30 degree temperature sensor. The wire that he drew coming from the triple pressure switch will connect ground if pressure goes too low or too high. The low side pressure switch is what the air conditioner uses to prevent evaporator freeze up anyway. I honestly think this will be the perfect solution to your problem. Two relays should cost you less than $10 and you are set my friend!
> While we are talking about his diagram, could someone give me a good explanation of what the Thermo Control Amp does? I have never seen this device before.


The thermo control amp is what the ECM reads as a thermometer. It is the black plastic sensor inserted in the evaporator core in such a manner for the most accurate control of the compressor so the evaporator will not freeze up but is just on the edge of that point. It is such an accurate set up that Nissan had a service bulletin on it once. The service bulletin was because at some interval during asymbly the sensor was placed about a 1/2 inch off from that sweet spot allowing the evaporators to freeze. That is why I suggest the thermo sensor to be as accurate as possible in a reasonable manner. The next step up would be a small logic board that could process the out put from that origional sensor to controle the compressor but at the point of a custom logic board you are at the price range of a new ECM.

The thermo control signal wire passes through the triple pressure switch so that in the event of an excessivly high pressure the switch will interupt the signal. Without the signal the ECM's programed logic is to shut off the compressor. 

*I forgot to add, my suggested fix is assuming that you have an accuret diagnosis and everything else in the system is in proper working order.*


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## Paquirris (Jun 16, 2008)

Spat, i had a problem on my a/c, it never turn it on, and i implemented the solution you gave us and it worked for few seconds then stop blowing cold air but the compressor continued engaged, i letf it running trying to find where was the problem then the high pressure relief valve when on and then stop, i did notice that the fan never worked when i turn on the a/c, i check the pressure on the lower side and is ok also i notice that the pressure goes down when i press the gas pedal but still no cold air nether the fan work when the a/c is on, i think is probably a clogged system, is there any in line filter on the refrigerant? could be the expasion valve, is this easy to replace/clean? i you have any info how to replace it i will appreciate, thanks for your help.
PS. my car is Altima 97.


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## spat (Oct 15, 2005)

Paquirris said:


> Spat, i had a problem on my a/c, it never turn it on, and i implemented the solution you gave us and it worked for few seconds then stop blowing cold air but the compressor continued engaged, i letf it running trying to find where was the problem then the high pressure relief valve when on and then stop, i did notice that the fan never worked when i turn on the a/c, i check the pressure on the lower side and is ok also i notice that the pressure goes down when i press the gas pedal but still no cold air nether the fan work when the a/c is on, i think is probably a clogged system, is there any in line filter on the refrigerant? could be the expasion valve, is this easy to replace/clean? i you have any info how to replace it i will appreciate, thanks for your help.
> PS. my car is Altima 97.


My first thought is likely a clogged expansion valve if the high pressure relief was activated. It is located in the evaporator box. Will need to evacuate system and remove evaporator to replace. Not difficult if you are mechanicly enclined. There is also a chance of other clogs but expansion valve is most common. I reccomend consulting with another experienced tech. These days I am having some issues with clear thinking and don't want to steer you wrong. Thats part of why I haven't been around the past several months. Plus I got issues with my now one and only vehicle that is a dam dodge! I miss my old D21 pick-up.


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## Garage Battle (Feb 25, 2004)

here is what is happening

please feel free to listen to this advice only


when your a/c is supposed to kick on, and your revs go up, and your fans turn on, its expecting the compressor to be kicked in and pulling from the belt. but it doesnt. your a/c clutch is wearing out. sad eh? 



cool thing is i bring you a solution.

Nissan Enthusiast Forums - A/C Failing in stop/go + heat. Temporary solution inside.










see that guy? I talk about him in the link. basically, soon as your car starts, that little guy gets 12v constant. problem is, as the clutch gets older, hes not man enough of a wire to engage the clutch. all you do is route the 'fog light' supply wire (also constant 12v) over to the AIR CON relay wire. depin the wire circled, and shove the foglight 12v wire in its place. done.


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## jdb8805 (Apr 12, 2009)

Guys the pictures are gone from the link above. I have a service manual and from what I can tell, pin 5 on the relay is the one that needs more power/voltage.

If I find another working (unused) fuse location, such as the fog lights, can I add a tap and a fuse and just jumper an extra wire over?


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## gsnorules (Jun 14, 2013)

*97 ALtima lEAK AT A/C DRYER*

I have a small leak at the dryer line where it bolts to the dryer (10mm) then runs up to the Condenser. Does this short line need to be replaced or does just need a O ring inside?


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## gsnorules (Jun 14, 2013)

My little line is leaking at the same spot at the dryer. They said it a Nissan item. Why did it take 3 times & 3 of the same part to fix this? Did they tel you?


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