Air conditioning
 

i have a red 83 rx7 with black interior, maybe some of you feel my pain when its summer time and you decide to hop in your car to go for a ride and it turns out its hot enough to bake cookies in there , anyway i was hoping if someone could help me, my ac pump wont turn on, the ac button lights up but there's no current going throught the fuse , whats happening?

ac
 

Most cars have to have enough "charge" in the system to turn the compressor on. My fc was like that. Try recharging it and the compressor may kick on.

Has it ever been 'swapped-over' to the newer, earth-friendly-er, Freon replacement? If it's running Refrigerant-134a (the new one vs. R12 - which is $$$), then you can buy a recharge kit with simple gauge at your local parts house. I would buy 2-3 cans just in case it's completely empty. Here's the quick rundown;

1) Compressor - there are 2 types of A/C installed in our cars, Japanese factory installed (Denso) and dealer/port installed - which carries a few names other than 'Denso'. The Denso compressors are more common and smaller in physical size. On the front edge of the compressor is the clutch mechanism which is an electromagnetic operated system to cycle the compressor on/off when the ECU calls for it. It runs longer when you have MAX A/C selected, shorter durations with lower fan speeds. This has a light on the dash A/C controls to let you know the compressor is set to run - but that light tells you nothing about the compressor in operation. At the front of the compressor are 2 plastic valve covers - BLUE (low pressure) and RED (high pressure). You charge off of the LOW PRESSURE side, to suck the refrigerant into the intake side of the compressor - this is important. The valves are different sizes to avoid you doing it wrong, but people never cease to amaze me.

2) Filter/Dryer - from the compressor, the compressed refrigerant goes to a black can about the size of a shaving cream can which is visible if you remove that round, black disk from the header panel in front of the radiator. On the top of the filter/dryer is a glass sight-hole used to see when the refrigerant flowing past there is a liquid (good) or is spraying (bad, too little refrigerant in the system). These are cheap, and should be changed as they accumulate water over time and need to be discarded.

3) Condensor - this is the thing radiator-looking thing in front of your real radiator, and allows a place for the compressed refrigerant to let out it's heat. As air comes in the front airdam, it blows past the hot liquid refrigerant which is under high pressure from the compressor, sucking out the heat and cooling it. From there, the high pressure lines continue on into the car through...

4) High/Low Pressure lines - high pressure line goes from the compressor -> filter/dryer -> condenser -> cabin evaporator. Low pressure goes from evaporator -> pressure switch -> compressor, where it cycles back through again. These have O-rings on each end where they attach which can sometimes go bad. O-rings can be replaced, but cheaper just to replace the entire line and call it a day. That is if you can afford it and like cold A/C blowing more often than not.

5) Cabin evaporator/expansion valve - This is where the magic happens. As that high pressure liquid refrigerant is flowing inside the A/C system, it gets sprayed through a tiny orifice called the expansion valve. This valve allows the liquid to expand into it's gaseous state, which any physics teacher can tell you - expansion is a cooling process. As the liquid expands into a gas in the Evaporator core, it gets cold. Nearly freezing, as a matter of fact. This evaporator core has your cabin air fan blowing air past it, which removes the heat from the passing air and blows it in your face as now cold air. Now that refrigerant, being expanded out into a gaseous state, is under low pressure and is on the suction side of the compressor.

6) Pressure Sensor - This is right by the clutch master cylinder in front of the firewall and is a 2-wire switch that is Closed when pressure exists in the system on the low-pressure side. The purpose for this is to prevent the compressor from running when the system is dry - because it needs both liquid refrigerant flowing AND lubricant oil which is contained in the refrigerant . Your replacement R134a will contain the right amount of lubricant, but you can also add ultraviolet dyes and lubricants if you're trying to find leak (with UV light), and/or trying to lubricate the system. Don't bypass the Pressure Sensor, or you risk burning up your $$$ compressor (~$800 at the stealership, last time I checked, if they're even available anymore).

7) ***you know it had to be seven things, right?!*** Temperature differential - Normal A/C operation is based on the temperature drop between ambient air temp (outside air temp) and the vent duct temp. Good systems will get about a 30deg Fahrenheit drop compared to outside air temp - so if it's 100F outside, you can get down to 70F at the duct, while outstanding systems can do a little better than that. This is measured with any thermometer sitting on the center duct, and is a standard performance test for A/C operation.

More refrigerant in the system does NOT mean more cold - so once your gauges show in the green range, stop adding refrigerant (R134a). The system can only do so much, and adding too much refrigerant will overload the compressor as it tries to move all that gas and re-convert it into a liquid to cycle through the system.

Start there and good luck,

Nice break down Duck - thx!

Stu Aull
80GS
Alaska

Nice explanation longduck. I'll also add that when I add refirgerant to a system I have a
thermometer stuck in the center vents with the AC on max and blower on high. I watch the
temps to get the lowest reading. When it bottoms out and starts to go up, I stop and slowly
bleed the system down to get back to the lowest temps.

Update: i ordered a recharge kit and recharged the compresser, it still didnt kick on so i took the metal shroud in front of the radiator off and took a look at the pressure or level sensor, i tested the wires with my voltmeter, both sides read about 12 volts with the ac off, with the ac on one read 12 volts and the other read .10 of a volt, with compresor still not kicking on, so i took a screwdriver and jumped the sensor doing this activated the compresser clutch so again i went inside the car with the ac on max but with no luck/cold i hooked up the recharge kit again( wich has a guage) up to the runing compresser and the reading was in the blue at 50 psi and there seemed to be fluid flow in the looking glass on the dryer but no cold, any ideas?

Not enough pressure to enable the compressor to come on is my guess. Not sure what sensor
you jumpered but I suspect its the pressure sensor that protects the compressor from too
much/little pressure in the system.

Op doesn't say how much refrigerant was put in,seeing flow in sight glass is good,means compressor is pumping. Post back and tell us how much refrigerant has been put in. Could be two things happening here: 1) overcharged,50 psi suction side reading 2) expansion valve stuck in open position. Set of a/c gauges hooked up with lo/high side readings would go a long way toward diagnosing what's going on. If only 12-20 oz. refrigerant put in system from empty(assuming all is good with rest of system) would expect to see slight vacuum to 10,15 at most psi in lo side of system. At this point would not recommend putting any more refrigerant in system til you post back with how much you think you put in already. Happy to help here,will monitor this thread for your response.

...or, you could just ignore us like some guy who joined the forum back in Oct'14 and only has 44 posts.

Im very sorry ive been busy and my phone has been glitching out ill reply later today after I get out of work

LongDuck,am certain this smarmy post is directed at me, Didn't bother to look at my post count or when i joined, sounds about right,unable to understand why.....Only trying to help the OP here. "some guy"supposes some protocol has been violated,like not having "permission" to post helpful diagnostic procedures until a certain post count or time period has elapsed. Maybe you or someone else can enlghten me on this. Not interested in conflict,nor internet muscle flexing. Hope this isn't going to affect me posting and asking questions,or for help in future on this board. To the OP, hope you get your a/c sorted.....

LongDuck,my apology,thought your sarcastic comment was directed at me. Was reading this on my phone,and just reread the thread. Sorry... wasn't trying to be a d*** or thinskinned. I take it as teasing OP as he'd not yet responded....

Nahh, don't sweat it, man! It was meant in jest for the OP! Usually when someone posts for help and then disappears, it's because he got fed up and sold the car...

I'm glad he posted back, and hope we can all help to get his A/C up and running,

I just charged my '85 up from zero...the metal fitting on the compressor came off when I unscrewed the plastic dust cap!! lol... so I KNOW it was empty.

It took 2.5 of the small 12oz cans...I used to cheap stuff from wally's... So, approx. 30 oz? I guess. The pressure read 50psi on the cheapo gauge. and it blows pretty cold air...it is hot here, S. Florida.

new here...just figured it was relevant since I just did it a few days back.
thx. Sam

Thanks for posting that volume estimate, Sam. It may help others trying to estimate how much to add.

Welcome aboard!

So I got a new relay and that still didnt help, I jumped the compressor again and looked at guage that cam in the kit, with it running its up to 50 psi on the low side and the air conditioning doesnt get cold but the ac compresser heates up, overcharged maybe?

50 psi is good in mine.
Sam


'good' as in cold.

Possibly overcharged, or you have a plug somewhere in the system (filter/dryer - most likely). The compressor heating up is because it's not able to move enough Freon which also serves to cool the compressor.

All you've done so far is to recharge the system? Per my note above, you need to also be sure you're using the right Freon, as these cars originally came with R12 and had to be retrofit to R134a which is the ONLY stuff sold in stores these days. Thank the EPA in their finite wisdom.

Point being, if you're using the wrong Freon type - I'm not sure how you'd get it charged because the connectors are different, and you're supposed to evacuate the system complete before putting the new stuff in place of the old...

50 PSI is too much. A simple way to look at it is each psi on the low side is equivalent to the same temperature in fahrenheit. You want 32-40 psi on the low side. It is dependent on ambient temperature.

If you have 32-40 psi, you should have 40-45 degrees out of the vents.


https://cimg2.ibsrv.net/gimg/www.rx7...4c983f26d9.jpg



This chart is for R-134a, but R-12 is also pretty close.

it is usually between 91-94F here during the day...so 50 psi corresponds to the chart for my ambient temp, I think...the can had or maybe the cheapo gauge had a temp correction chart on it.

I sorta kept adding R-134 until it felt cold enough...lol..I think I remember, at around the beginning of the green arc on the gauge, it was not yet cold. (IDK, around 30 psi?) So, I increase the pressure until it was. however, still in the green arc, but on the high side, not the low, (corresponding with the gauge correction for my outside temp)

Looks like the OP lives up North, so perhaps 50psi is a bit too much, for his ambient temp...IDK....its friggin' hot around here right now!

Did you add oil when adding refrig? Did pull a vacuum to make sure it doesn't leak? Did you replace the dryer/expansion valve and all the orings?

You need to do all these things to know its setup right for success.

I didnt replace anything I was hoping it.only need more.coolant for it to activative but it lookes like its bigger than that

It doesn't work that way. AC repair is a precise and tedious business. You have to do it properly, or not at all.

Let's put it this way. The average AC repair on almost any car at a shop costs about $1000. I'm not talking about a simple recharge, but a general repair. $1000 is the norm.

Your electronics may be fine and working as designed to protect your compressor due to some issue in the rest of the system.

I know you have a 1983, but I have the factory 1984 AC troubleshooting manual for the Lone Star Mfg. and Nippondenso AC units. I'll need to scan it first.