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Discussion Starter #1
Hello,
I did some searching but couldn't find an answer to this. I bought my 78 280z in 2014. The dealer I purchased it from said it needed AC work and this was completed and the car was shipped to me. The AC blew cold until the past year when it started blowing warmer. I took it to a local shop for a check and charge. They asked if it had a conversion and I told them I thought it did. It needed a pound of R134 it blows a little colder but not great like before. They said it could be a bad evaporator valve.



How can I check to see if this Z was converted to R134?



Thanks,
Pete
 

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if it was done right, there should be R134 quick release type connections installed over the old R12 types. That and a note attached specifying the oil used and the amount of R134 used.


Assuming all that was not done, the next option would be to completely evacuate the existing gases, drain the oil from the compressor, flush the entire system, prob get a new condenser, a universal fit parallel flow would be good, new drier, new hoses, clean the filter at the joint of the hard lines of the high side near the firewall (there is a small screen in there), evac the system and check for leaks, then recharge with about 80% IIRC the amount recommended for R12.


If you are unlucky, then the expansion valve could be bad, generally speaking you can tell this by odd reading of the gauges assuming everything else is ok.


IF the expansion valve is bad, then you have to decide if you want to risk an used one if you can find it, OR pop for a new evap unit that uses a standard easy to get expansion valve., that will set you back about 250-350 if you can find one (they are out there new).


Cheap route would be just to evacuate, flush, drain oil, new drier, new oil (ester), pull vacuum, charge and hope.
 

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Discussion Starter #3
if it was done right, there should be R134 quick release type connections installed over the old R12 types. That and a note attached specifying the oil used and the amount of R134 used.


Assuming all that was not done, the next option would be to completely evacuate the existing gases, drain the oil from the compressor, flush the entire system, prob get a new condenser, a universal fit parallel flow would be good, new drier, new hoses, clean the filter at the joint of the hard lines of the high side near the firewall (there is a small screen in there), evac the system and check for leaks, then recharge with about 80% IIRC the amount recommended for R12.


If you are unlucky, then the expansion valve could be bad, generally speaking you can tell this by odd reading of the gauges assuming everything else is ok.


IF the expansion valve is bad, then you have to decide if you want to risk an used one if you can find it, OR pop for a new evap unit that uses a standard easy to get expansion valve., that will set you back about 250-350 if you can find one (they are out there new).


Cheap route would be just to evacuate, flush, drain oil, new drier, new oil (ester), pull vacuum, charge and hope.
Dave,
Thanks for the response. Based on what I'm seeing in the window of the Receiver Drier and what the tech said about the low side pressure I think the Expansion Valve is bad and yes I've had zero luck trying to source one. The Z is in excellent condition being from Arizona so she is worthy of the fix. Just replaces the shocks, springs, bushings, breaks, new braided SS break lines.
Pete
 

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if you are sure its the exp valve then you may want to invest in one of those new evaps I mentioned. they can be found on Ebay.
I did a video on testing one, not sure how accurate a test it was but I could at least tell if the exp valve was doing something.


https://youtu.be/FJRvE7qHHGc?t=210
 

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If you want to get this deep into it: The expansion valve can be removed and disassembled to inspect and/or clean. It's fairly simple and can be done without pulling the evap core or the copper tubes feeding the evaporator. Care needs to be taken in marking the exact position of the adjustment screw, but it's actually a pretty simple mechanism. One just needs to remove the center finisher and the ducting for the center vents to expose the evap core. The expansion valve is in front of the evap on the right side.

The filters that are inline are there to protect the expansion valve - receiver/dryer and the screen on the liquid line fitting at the firewall - but if refrigerants and oil were mixed, there could be a gooey mess in there. I'd start by checking the small screen filter in the liquid line at the firewall.
 

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Ditto on the servicing of the expansion valve you need to make sure you can put the screw in orifice piece back where it started. I would measure it from the top of the flare fitting AND do a turns count (till it bottoms out so you can reset back to the exact number of turns back out. The only thing that can go wrong besides rust or gunk is if the little bulb loses its charge and will no longer operate the needle. That was what I was looking for in the video (the cold spray was on the bulb).
 

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Discussion Starter #8
Well I looked around with the info given and the compressor is the original unit. It's marked with R12 on it for coolant. There are no "quick release" fittings over the original Red and Blue connections.



So, I have R134 added to an R12 system. From what I read this will degrade internal seals. I'm going to have the system emptied and have it converted.
 

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Something here doesn't make sense.

What kind of ignorant AC shop would put R134 into an R12 system? Was the refill done by some shade tree Bubba?

When a system is converted, the installer ALWAYS changes the input connections. ALWAYS. No exceptions. That's how they do the job.

If the connectors were factory original, that is confirmation that it is still an R12 system - and no one who knows anything about AC would put R134 into it.

My 83 still runs R12. When I finished a 4-year project on it last year, I found a local shop that is licensed for R12 and had it filled. No problem, cost was $200. Runs and works just fine, thanks.
 

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Discussion Starter #11
Something here doesn't make sense.

What kind of ignorant AC shop would put R134 into an R12 system? Was the refill done by some shade tree Bubba?

When a system is converted, the installer ALWAYS changes the input connections. ALWAYS. No exceptions. That's how they do the job.

If the connectors were factory original, that is confirmation that it is still an R12 system - and no one who knows anything about AC would put R134 into it.

My 83 still runs R12. When I finished a 4-year project on it last year, I found a local shop that is licensed for R12 and had it filled. No problem, cost was $200. Runs and works just fine, thanks.

Here is a photo of the connections. I have zip AC experience. These connections looked original to me.



Pete
 

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Anyway if its not blowing cold you have to do proper diagnostics. Since it looks like converted (based on the picture posted) You can hope it was done right. 1st order of business should be a pressure test high and low to see what is going on. A lot if clues can be gotten from the high and low pressure readings. The most likely issues would be a leak losing Freon, a clog in the system, water in the system, or a compressor not working. The key will be to figure out which of those or maybe even all of those. A good shop should be able to diagnose this and take care of it, but it will not be cheap.
 

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Discussion Starter #14
Dave, I had it checked as I thought it was low on coolant. The high side was good but the low side was drifting into negative pressure. The fella said it could be the valve. I looked at the troubleshooting algorithm in the FSM and believe it's the valve. Compressor looked fine according to the fella who checked it.
 

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If its the valve, you maybe able to fix it, but its going to require evacuating the Freon, flushing, check the filter screen, removing the Tvx, a pretty big job but not hard to do. The biggest challenge will be having to remove the expansion valve. remove the finisher to get access and use flare nut wrenches so as not to destroy the fittings. You might want to test the expansion valve to see if it flows AND responds (see my video).


The conversion risk gunk being formed by incompatible oils and freons. I would replace all the under hood parts, at least the hoses/drier/condenser. even the compressor would not be a bad idea for a conversion. Not saying you have to, but its the best way to know for sure that its going to work.


As mentioned you can get a new evap with a reg expansion valve, doing that would essentially give you a all new AC.
I have tried to find cheap evaps, but seems the only thing that fits are the expensive ones built just for z cars. they are not easy to find and expensive when you do. I got an ALL ALUM type, there are others made from copper. I assume the alum is better since the factory is that way, but that's just me. See what your AC guy says. I am not an expert, just know what I have done messing with my own stuff.
 
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