Rebuilding 1977 280Z A/C

[jgkurz]

Hi all, Earlier this summer I decided to rebuild the air conditioning in my 77 280Z. My desire was to stay with R12 and replace the compressor and receiver/drier. I found a brand new Nissan compressor from a ZX that was almost a bolt in except on a ZX the high and low side are swapped ont he compressor. Weird but easy to resolve with extended hoses. Next was my receiver/drier. For some reason the 77/78 280Z receiver/driers are different from all the other Z cars. I could not find a new, rebuilt or reman unit ANYWHERE. Ultimately I decided to have my rebuilt by a guy in Texas. It was a bit more cost but allowed me to use all my original copper tubing. I had the system charged up and initially got decent results. Vent was blowing at 39degF on an 85degF day.

 

Here's the high and low pressure readings. I think the low side may be a bit too low.

 

 

I took the car for a drive and the temp through the center vents would not go below 70degF. The R12 looked perfect in the sight glass . (no bubbles or low freon indicated). I also believe I have the correct amount of oil in the system. My guess is that my expansion valve is failing. I discharged the system and pulled out the expansion valve. It looked old but not necessarily bad. I'm not sure you can visually inspect an expansion valve. I found no debris or particulate that could clog or jam the valve.

 

Here's a pic of the current expansion valve:

 

 

Fortunately I was able to find a used replacement from Danny's Datsun in Roseburg Oregon. I will put the the replacement valve in and see if it makes a difference. If any of you are knowledgeable about Z car A/C please impart your wisdom.

 

Thank you.

[zcarnut]

First, the pressure readings are within the normal ranges so I agree that the expansion valve could be sticking closed. The only way to confirm this is to replace the expansion valve.

 

You could also have a restriction between the receiver/drier and the evaporator. Debris from your “rebuilt†receiver/drier may have clogged the screen filter at the input of the evaporator. Remove it and check for desiccant particles. This will look like course sand packed into the inlet screen.

 

Did you flush out your evaporator during the rebuild?

 

Did you pull a good, deep vacuum before you re-charged? You could have some moisture in the system.

 

The ZX compressor requires less oil than the earlier (280Z) one. Did you take this into account?

[jgkurz]

First, the pressure readings are within the normal ranges so I agree that the expansion valve could be sticking closed. The only way to confirm this is to replace the expansion valve.

 

I ordered a used/replacement exp valve from Danny's Datsuns. Hopefully it will do the trick.

 

You could also have a restriction between the receiver/drier and the evaporator. Debris from your “rebuilt†receiver/drier may have clogged the screen filter at the input of the evaporator. Remove it and check for desiccant particles. This will look like course sand packed into the inlet screen.

I have not check the screen. Thank you for the advice.

 

 

Did you flush out your evaporator during the rebuild?

No. I didn't even know you could. I may try to do a flush before a recharge again.

 

Did you pull a good, deep vacuum before you re-charged? You could have some moisture in the system.

I pulled vacuum for several hours to remove all moisture.

 

The ZX compressor requires less oil than the earlier (280Z) one. Did you take this into account?

 

I did. I assumed there was residue oil in the system then added roughly 4oz.

 

Thanks for the input.

[jgkurz]

Any thoughts on whether I should replace the o rings? They all visually look fine.

 

I have not check Nissan or MSA yet but I did find a kit at Black Dragon.

 

http://www.blackdragonauto.com/icatalog/z/full.aspx?Page=78

[jgkurz]

I just checked the screen and it was clear. Whew!! My expansion valve should be here tomorrow, just in time for 90deg F weather. Should be a good test.

[jgkurz]

I just checked the screen and it was clear. Whew!! My expansion valve should be here tomorrow, just in time for 90deg F weather. Should be a good test.

 

Well folks, I'm a little bummed. The new expansion valve didn't do squat. I have the same problem. The low and high pressure gauges read normal, no leaks, bubbles or plugged screens. The evaporator gets to about 60deg F but that's as cold as it will go. The only symptom that MIGHT be an indication of an issue is the fact that we can't get more than about 1lb of R12 in the system before it's full. I had the system evacuated professionally 3 times then recharged 3 times. According to the Nissan manual the systems should take 1.4 - 1.8lb R12.

 

My hunch is that I have too much oil in the system. The only way to solve that is to have everything flushed which will cost $300.00 to $500.00. Man what a pain.

[zcarnut]

Sorry to hear that, John.

 

Did you flush out the evaporator like you said you were going to do? With the expansion valve removed, this is fairly easy to do.

 

I’m still leery about the rebuilt receiver/drier. I’ve used the aftermarket one from Four Seasons before. You have to re-use your old under pressure switch. There’s one on fleaBay:

 

http://cgi.ebay.com/ebaymotors/77-NISSAN-280Z-A-C-Receiver-Drier-FOUR-SEASONS-33286_W0QQcmdZViewItemQQ_trksidZp3286Q2em20Q2el1116QQhashZitem2c50b99a3bQQitemZ190332901947QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

 

Before you do any disassembly, I would go ahead and add some more R12. The ZX compressor is internally larger that the 280Z one, so don’t go by what the manual says. Just keep an eye on the high side pressure.

 

I assume that you have good airflow across the condenser and evaporator coils.

[jgkurz]

Sorry to hear that, John.

 

Did you flush out the evaporator like you said you were going to do? With the expansion valve removed, this is fairly easy to do.

 

I’m still leery about the rebuilt receiver/drier. I’ve used the aftermarket one from Four Seasons before. You have to re-use your old under pressure switch. There’s one on fleaBay:

 

http://cgi.ebay.com/ebaymotors/77-NISSAN-280Z-A-C-Receiver-Drier-FOUR-SEASONS-33286_W0QQcmdZViewItemQQ_trksidZp3286Q2em20Q2el1116QQhashZitem2c50b99a3bQQitemZ190332901947QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

 

Before you do any disassembly, I would go ahead and add some more R12. The ZX compressor is internally larger that the 280Z one, so don’t go by what the manual says. Just keep an eye on the high side pressure.

 

I assume that you have good airflow across the condenser and evaporator coils.

 

The local Portland, OR A/C guru's will charge me about 500.00 to do an oil/R12 flush and refill. They are a different shop from the one by my house where I have gone previously. Also, they don't like working on custom applications like my Z without being paid big $$$. The $500.00 quote assumes an OEM setup and not with all my intercooler pipes and such. Who knows what they'll say when they see my car in person. Most likely I'll get some BS about no warranty or best effort. I really was hoping the expansion valve was the easy fix but I guess not.

 

To answer your airflow question, I would say my condenser is getting adequate but not excellent airflow. When I am on the highway I have plenty of air flow through the condenser and my evaporator temp can only manage 60deg F. From this I assume my consensor temp is not the issue.

 

The receiver-drier from ALL aftermarket shops including eBay show for my 77Z are not correct. I don't know why but everyone sells the earlier version with the inlet tube in the middle of the cylinder. My inlet, outlet and pressure switch are all on top of the cylinder. This is how all late 77 and 78 Z's were setup. Nissan, Beck Arney, Worldpac, Black Dragon, MSA...etc all sell the incorrect receiver-drier. Because of this I had mine rebuilt by a reputable shop (At least I hope)

 

When we filled my system we based the amount on the sight glass and high pressure reading. I doubt we have too much R12 but I'm not an expert.

 

BTW, I appreciate your input and advice. You have been very helpful. If indeed I have too much oil in the system I'm not sure how to get it out of the compressor, receiver-drier, condenser and evaporator. I find it hard to believe that a flush would pull it all out even if I pay $500.00+

[hughdogz]

Hi John,

 

Have you considered switching from R-12 to R134a?

 

I believe all that is involved is to change to a different style filler fitting (I've seen by buddy Bryan do it for a Bimmer)

 

You can then buy 134a off the shelf at almost any auto parts store (for not much $$ by comparison).

 

Just a thought...

[zcarnut]

...If indeed I have too much oil in the system I'm not sure how to get it out of the compressor, receiver-drier, condenser and evaporator...

 

 

If you elect to "do it yourself", here's a write up I did for our club newsletter:

 

AC Flushing

 

Everyone agrees that too much oil in the AC system will decrease performance. Systems that have signs of debris and contaminants from compressor failure or desiccant breakdown should be thoroughly flushed.

 

You should remove and flush the condenser, evaporator and the hoses and lines where practical. Remove the expansion valve before flushing the evaporator. You should never flush the expansion valve or the receiver-drier. These are items that need to be replaced rather than flushed.

 

Likewise, do not flush the compressor. Remove the compressor and drain it out the ports by turning it over and rotating the compressor shaft. Add about an ounce or two of R12 refrigerant oil to the suction inlet and rotate by hand to flush out any debris out of the discharge outlet of the compressor.

 

Flush the system components with either an AC flushing agent or mineral sprits. AC shops have used mineral spirits to flush AC systems for many years with no problems. It is a relatively safe product and a good cleaner. Although mineral spirits are flammable and are slow to evaporate, they are made from the same base material as R12 mineral oil so small traces of mineral sprits left behind will do no harm.

 

Flushing Procedure:

 

* Use a plastic “squeeze†bottle to squirt the solvent into the component.

* Flush in a reverse direction to refrigerant flow first to dislodge any material caught inside.

* Using a shop air blow gun at about 60 psi, blow the solvent through the component and catch it in a shop rag.

* Hold the blow gun tight at one end of the component.

* Hold our finger over the other end until it builds up pressure.

* Release your finger letting it blow off (or "pop") pressure.

* Repeat until there is no sign of solvent coming out.

* If available, purge the flushed component with nitrogen gas to remove any moisture left behind by the shop air.

 

Note: Because of their small tube diameter, some condensers are very difficult to flush and may need to be replaced if the above flushing procedure is ineffective. It is cheaper to replace the condenser than to have debris left in the system which may damage the other AC components.

[jgkurz]

If you elect to "do it yourself", here's a write up I did for our club newsletter:

 

AC Flushing

 

Everyone agrees that too much oil in the AC system will decrease performance. Systems that have signs of debris and contaminants from compressor failure or desiccant breakdown should be thoroughly flushed.

 

You should remove and flush the condenser, evaporator and the hoses and lines where practical. Remove the expansion valve before flushing the evaporator. You should never flush the expansion valve or the receiver-drier. These are items that need to be replaced rather than flushed.

 

Likewise, do not flush the compressor. Remove the compressor and drain it out the ports by turning it over and rotating the compressor shaft. Add about an ounce or two of R12 refrigerant oil to the suction inlet and rotate by hand to flush out any debris out of the discharge outlet of the compressor.

 

Flush the system components with either an AC flushing agent or mineral sprits. AC shops have used mineral spirits to flush AC systems for many years with no problems. It is a relatively safe product and a good cleaner. Although mineral spirits are flammable and are slow to evaporate, they are made from the same base material as R12 mineral oil so small traces of mineral sprits left behind will do no harm.

 

Flushing Procedure:

 

* Use a plastic “squeeze†bottle to squirt the solvent into the component.

* Flush in a reverse direction to refrigerant flow first to dislodge any material caught inside.

* Using a shop air blow gun at about 60 psi, blow the solvent through the component and catch it in a shop rag.

* Hold the blow gun tight at one end of the component.

* Hold our finger over the other end until it builds up pressure.

* Release your finger letting it blow off (or "pop") pressure.

* Repeat until there is no sign of solvent coming out.

* If available, purge the flushed component with nitrogen gas to remove any moisture left behind by the shop air.

 

Note: Because of their small tube diameter, some condensers are very difficult to flush and may need to be replaced if the above flushing procedure is ineffective. It is cheaper to replace the condenser than to have debris left in the system which may damage the other AC components.

 

Steve, I can't thank you enough for taking the time to respond. I will heed your advice this time and give my R12 system one more try. I may go R134 at some point like Hugh suggested since I can get the product at a local parts store.

[woldson]

R134a will not be as effective as r12.

So if you can't get the r12 going good, chances are a 134a system will make things warmer. (since we are going into winter, maybe a good thing?! LOL)

[Savage42]

John, if you can get down to Eugene, Dustin will be more than happy to do your A/C in either R-12 or convert to R134 for half the price of those other guys. He has no problem doing custom work, as he's currently putting a supercharger on the VG powered 510 at the shop. Just an option. His number is 541-688-9321

[jgkurz]

John, if you can get down to Eugene, Dustin will be more than happy to do your A/C in either R-12 or convert to R134 for half the price of those other guys. He has no problem doing custom work, as he's currently putting a supercharger on the VG powered 510 at the shop. Just an option. His number is 541-688-9321

 

Hmmmmm. That's a great idea. I just can't stand dealing with people who don't understand that a custom car is not the same as an OEM car. In other words, I'm not going to stay in the waiting room while someone works on my Z. The only way that would happen is with someone like Dustin. Thanks for the idea.

[jgkurz]

R134a will not be as effective as r12.

So if you can't get the r12 going good, chances are a 134a system will make things warmer. (since we are going into winter, maybe a good thing?! LOL)

I agree. That's the main reason I have not converted.

[Savage42]

Dustin does both R12 & R134a. He's helping me build my A/C setup and the only stock part I'm using the Evap core setup. Everything else will be custom, including lines, condensor, drier, etc. He is the man and his shop rules. Probably why all 7 techs and 11 racks are full most of the time. He's not afraid of ANY custom work. He'll also stand behind his 12 month warranty! He also has one of the lowest shop rates in town, some $20/hr less than the dealerships and specialty shops, too.

[rsicard]

jgkurz: The only thing that seems to have been passed over is the condenser. It is the item that exchanges heat into the air. It is VERY important that it work efficiently. Likely the one that you have is an OLD design. The newer designs are much more efficient. Try a new one from someone like Vintage Air.

[Savage42]

I have to measure and see what condensor will fit easily up front, with both fittings on the driver's side, so I can cleanly run the hoses along the frame rail and have them tucked out of the way. It'll be a newer model, for sure.

[woldson]

My 83 ZX works quite well with r134 after conversion this summer. Mention this due to condenser, which is stock.

Yes, r12 would have been better, however, it was for my wife and it is satisfactory.

[jgkurz]

jgkurz: The only thing that seems to have been passed over is the condenser. It is the item that exchanges heat into the air. It is VERY important that it work efficiently. Likely the one that you have is an OLD design. The newer designs are much more efficient. Try a new one from someone like Vintage Air.

 

I'd change out my condenser if necessary, but I'd like to get the system working to OEM capability first. There is an underlying problem that needs to be fixed before I consider any upgrades. In it's current state, the system will only bring the evap down to 60deg F with an outside temp of 90deg F. It should be capable of at least 40deg F. My guess is that the system has too much oil or my "professionally rebuilt" receiver/drier is somehow a problem. I'm reaching for anything at this point so I'll probably have Dustin (mentioned above) take a look when I can make the two hour drive down to Eugene.