# 1984 300ZX A/C Problems



## FICD (Mar 14, 2012)

How are you all doing? I am new to the forums and hope to be welcomed with open arms. 

I have an A/C problem

I have tested the compressor, which turns on. I suspect a leak somewhere because when my mechanic (whom is NOT an A/C mechanic) and I evacuated and refilled with freon we noticed both the high and low side ports to the compressor get really hot. The compressor would not turn on by itself so we connected it to the battery for a very very short time. Well, I did some research and found that if there is air in the system, (leak) those lines would get very hot indeed. Found out that the high side Schroeder valve was broken because immediately after removing the refill nozzle, it sprayed out. We thought it was going to spray out freon, but lo and behold, we felt absolutely nothing but air! Even with the compressor on, it would not suck in any freon, not sure what the deal is there. Now before the peanut gallery tells me to 'just take it to an a/c repairman', we did. 2 in fact. First one told us that there might be an electrical problem because the compressor would not kick on when the system was under pressure and wouldn't touch it because they don't work on electrical stuff. Second one wanted to charge me to the number of 1050 to fix my A/C, which my mechanic (whom was present both times) said that was retarded and outrageous and that we would be better of just restoring the a/c system with *almost* all new parts.

Sooo, here's what I have replaced or plan on replacing:

Receiver/Drier (replaced)
low pressure cut off valve (replaced)
compressor relay (replaced) 
Schrader valve kit (have them, but not yet installed...need schrader valve core tool which I just found out existed yesterday  )
condenser (needs to be replaced)
evaporator (needs to be replaced)
expansion valve (needs to be replaced)
---These three items listed above that I need will cost me about 300, which is perfectly reasonable---

I performed the a/c diagnostics for the sensors and it appears that the only sensors that work are the hot water temp and the driver side floor sensor. The sunload sensor might work, but it keeps bouncing back and forth from 30 and 31. My ambient temp display is stuck on -56 and I can't find ANYWHERE online for info on what that's about. I think the ambient temp sensor outside under the bumper has come loose. 

The heater and all its systems work perfectly. I was a very happy camper this winter. But this summer is coming up and living in Texas with 108+ summer days...man I need my A/C. 

I think my actuators work, because when my feet get too hot the auto temp sensor will turn on the vents. The problem is that the air comes out strong on the far left and right vents and weak on the two central vents...any idea what that is all about?

I would like to do this right, and replace all the broken sensors but, I do not know where to get them. Any recommendations? 

So to recap, here are my questions:

1. Do you have any idea what is preventing the compressor from turning on?
2. What else should I replace on the a/c or what should I look out for when I perform the leak (UV) test?
3. Do you have any idea why the air blows weak in the two central vents?
4. Where can I get replacement (prefer new) auto climate control temp sensors?
5. What could cause the A/C system to not pull in enough freon? My system barely pulled in one can of R134a. Could there be a clog somewhere? If so, what are the culprits? 
6. Are there any other sensors I need to replace? I keep reading about this thermo switch. 
7. Is it possible to retrofit a cabin air filter? That stinky outside air is killing me (literally). 
8. What do you think about the Amb Temp display being stuck on -56?
9. Was I correct about my hunch that the system was full of air when the high and low side (AND freon can) got hot?

I am SO sorry that its kind of jumbled together. That's the only way I could tell my story without forgetting anything. 

Thank you in advance for anyone deciding to answer my questions (instead of telling me to visit yet another a/c repairman)

BTW: My mechanic specializes in 300zx mechanical repairs. He is my good friend and I trust him with my car as well as my life. Although he knows nothing about the a/c systems, he can replace all the physical parts without a problem. This is a learning experience for the two of us.


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## rogoman (Dec 16, 2004)

First of all you need to have a good vacuum pump for proper system evacuation. Then you need to have an A/C manifold gauge set. Attach the gauges and run the vacuum pump for about 20 minutes until the low gauge reading shows around 29.9 inHg. Let it stand for about 10 minutes to make sure there are no leaks.

With the engine shut off, open both high and low valves; fill the system with one can. Close high valve and start engine. The reading should be around 30 to 40 psi on the low side and the compressor should be running. If the pressure is too low, the compressor may not start up; if so, fill slowly on the low side.

Once everything is up and running, the pressure readings should be around 35 psi on the low side and around 200 psi with an outside temperature of 90 degrees F and a relative humidity of around 80 %.


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## nicko6113 (Jun 30, 2012)

I don't know if you got it to work but if I remember if the digital control unit thinks its colder than 32 degrees out it will not engage the compressor. If its the temperature sensor that just needs to be replaced. I had to replace my control unit 3 times as one died. One had a bad circuit and would not engage the AC.


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