Ken Smith Posted December 2, 2016 Share Posted December 2, 2016 I have an a/c system for my 1975 280z that is a factory type that cam out of another 75 280z. I've been told that I should replace the receiver drier since it is 40 years old and probably no good. Problem is it has the low pressure switch and all the new ones do not have this provision along with the same fittings for the copper tubing. I did find a few places that say they have the correct replacement but after trying to buy one they are out of stock. None of the dealers have them either. Anyone have a solution other than swapping out for aftermarket and trying to retro fit the copper lines? Also way to add a low pressure switch that will work with the factory harness? I'm open to suggestions but if you have done this I am all ears.......thanks Quote Link to comment Share on other sites More sharing options...
cgsheen Posted December 3, 2016 Share Posted December 3, 2016 Firstly, it's not actually a low pressure switch. It's on the liquid (high pressure) line of the A/C system and it is in fact a high-pressure switch. It breaks the electrical circuit to the compressor if the liquid line pressure is too high. There is no "low pressure" protection in these early Z factory systems. Secondly, I know you'd love to just put in a stock replacement that won't require any modification - after all, then it's just "un-bolt one and bolt another one in" - but you're not likely to find a stock replacement. I've been that route... You're probably going to need to find a replacement that will still be available years from now and re-do at least part of the liquid line routing to fit the new one. There are multiple products available that you could substitute that also have provisions (ports) for your threaded pressure switch. The liquid lines are made from standard refrigeration tubing and use standard flare fittings. Coming from a plumbing and HVAC background, this is pretty simple stuff for me. I can understand that it can be daunting for some though. Still, any refrigeration shop worth their salt (or HVAC tech as a side job) should be able to handle the liquid line modification. Completely new copper refrigeration tubing can be easily formed and flared to fit the new part... And possibly re-forming (bending) the existing tubing could be all that's required. 1 Quote Link to comment Share on other sites More sharing options...
Ken Smith Posted December 5, 2016 Author Share Posted December 5, 2016 Firstly, it's not actually a low pressure switch. It's on the liquid (high pressure) line of the A/C system and it is in fact a high-pressure switch. It breaks the electrical circuit to the compressor if the liquid line pressure is too high. There is no "low pressure" protection in these early Z factory systems. Secondly, I know you'd love to just put in a stock replacement that won't require any modification - after all, then it's just "un-bolt one and bolt another one in" - but you're not likely to find a stock replacement. I've been that route... You're probably going to need to find a replacement that will still be available years from now and re-do at least part of the liquid line routing to fit the new one. There are multiple products available that you could substitute that also have provisions (ports) for your threaded pressure switch. The liquid lines are made from standard refrigeration tubing and use standard flare fittings. Coming from a plumbing and HVAC background, this is pretty simple stuff for me. I can understand that it can be daunting for some though. Still, any refrigeration shop worth their salt (or HVAC tech as a side job) should be able to handle the liquid line modification. Completely new copper refrigeration tubing can be easily formed and flared to fit the new part... And possibly re-forming (bending) the existing tubing could be all that's required. Do you happen to know which ones will work with the high pressure switch? I'm more concerned with the fittings especially for the pressure switch. I didn't see anything available that has the switch and I don't know if they are all adaptable. Thanks.... Quote Link to comment Share on other sites More sharing options...
cgsheen Posted December 5, 2016 Share Posted December 5, 2016 (edited) All the receiver/dryer needs is a 1/4" NPT female thread port to screw the switch into. (This port also can be anywhere after the condenser in the liquid line - it doesn't have to be in the receiver, it's just more convenient. (that means a fitting could be silver-soldered into the 3/8 copper tubing)) I've bought a few dryers in the past that have 2 extra threaded ports which could stay capped off or have the cap (plug) removed for a switch installation. Edited December 5, 2016 by cgsheen Quote Link to comment Share on other sites More sharing options...
Ken Smith Posted December 6, 2016 Author Share Posted December 6, 2016 All the receiver/dryer needs is a 1/4" NPT female thread port to screw the switch into. (This port also can be anywhere after the condenser in the liquid line - it doesn't have to be in the receiver, it's just more convenient. (that means a fitting could be silver-soldered into the 3/8 copper tubing)) I've bought a few dryers in the past that have 2 extra threaded ports which could stay capped off or have the cap (plug) removed for a switch installation. Thanks, I'll start looking for one with the 1/4" NPT female port. I really want to keep it original looking. I have the original Receiver/drier and wonder if it can be checked to see if it is still good. Was supposedly just removed from a closed system as all the other components I bought from a salvaged 75 280z. Thanks again for your help. Quote Link to comment Share on other sites More sharing options...
Chickenman Posted December 6, 2016 Share Posted December 6, 2016 (edited) I managed to find a supplier in Canada that had stock on the correct 4 seasons receiver/drier( #33286 ) for 75 and 76 280Z's. These have the correct positioning of the connections as in your pictures. Price was dirt cheap as well. I'll have to look through my receipts and will post the link a bit later. These are normally very hard to find. The later styles are far more plentiful Edit: It was from a company called " The Wrench Monkey ". They still show them in stock for only $63.29 CDN. I'd send them an E-mail to confirm stock levels. https://www.thewrenchmonkey.ca/products/auto-parts/four-seasons/33286/ Edited December 6, 2016 by Chickenman Quote Link to comment Share on other sites More sharing options...
Ken Smith Posted December 6, 2016 Author Share Posted December 6, 2016 I originally went on 4 seasons website and they didn't show that unit. I'll try and order the one in Canada. Thanks........ Quote Link to comment Share on other sites More sharing options...
TimZ Posted December 6, 2016 Share Posted December 6, 2016 I originally went on 4 seasons website and they didn't show that unit. I'll try and order the one in Canada. Thanks........ You didn't say what refrigerant you were planning to put back in it, but if you go R134 you'll also need a different pressure switch. R134's "normal" system pressures are higher than R12. Quote Link to comment Share on other sites More sharing options...
Ken Smith Posted December 6, 2016 Author Share Posted December 6, 2016 (edited) You didn't say what refrigerant you were planning to put back in it, but if you go R134 you'll also need a different pressure switch. R134's "normal" system pressures are higher than R12. I didn't know that. R12 I believe is hard to find as I live in California and I think it's probably illegal here. Or very expensive at best. Any ideas on a pressure switch that will work with original type drier? If I can get R12 for a fair price I understand it actually is better than R134. If that's the case I will stick with the R12. Edited December 7, 2016 by Ken Smith Quote Link to comment Share on other sites More sharing options...
Chickenman Posted December 7, 2016 Share Posted December 7, 2016 (edited) I use R12A from Redtek in my Z . Direct replacement for R12 plus it's more efficient than R134. Lower head pressures and colder temps than R134 as well. " R12 " has been banned in Canada for a long, long time. I've used RedTek R12A for about 10 years in my Audi A4. Zero issues and freezing cold temps. Mots of my friends use it for a quick charge up as well. R12A is a very common item in Canada. Should be in the USA as well. 6oz can ( 18oz equivalent ) costs me $6.85 CDN. http://www.redtek.com/home.html Tech Info: http://www.redtek.com/techinfo_refprop.html Edited December 7, 2016 by Chickenman Quote Link to comment Share on other sites More sharing options...
TimZ Posted December 7, 2016 Share Posted December 7, 2016 I didn't know that. R12 I believe is hard to find as I live in California and I think it's probably illegal here. Or very expensive at best. Any ideas on a pressure switch that will work with original type drier? If I can get R12 for a fair price I understand it actually is better than R134. If that's the case I will stick with the R12. Any overpressure switch made for R134 should do. The main problem (at least for me) was that I had trouble finding a switch with the same size fitting so I had to make an adapter. I also went with a generic receiver/dryer that didn't have a port for the switch, so I just soldered in a tee in the copper line and soldered in the proper size female brass fitting on the tee. It's certainly not an insurmountable problem, it was mostly annoying as I found out about the switch _after_ I had the whole system together and charged. Also I've been running R134 for several years now and it works just fine, and I'm not dependent on going to a shop that will charge me a fortune to work with the r12. There IS prep work that needs to be done as far as flushing the old system out, and what oil to use for the conversion, but this is really well documented on the web. Quote Link to comment Share on other sites More sharing options...
Ken Smith Posted December 7, 2016 Author Share Posted December 7, 2016 I managed to find a supplier in Canada that had stock on the correct 4 seasons receiver/drier( #33286 ) for 75 and 76 280Z's. These have the correct positioning of the connections as in your pictures. Price was dirt cheap as well. I'll have to look through my receipts and will post the link a bit later. These are normally very hard to find. The later styles are far more plentiful Edit: It was from a company called " The Wrench Monkey ". They still show them in stock for only $63.29 CDN. I'd send them an E-mail to confirm stock levels. https://www.thewrenchmonkey.ca/products/auto-parts/four-seasons/33286/ Well, I sent an email and here is their response as I suspected: Hi Ken, Unfortunately, we are currently not showing stock on this item. We contacted the manufacturer and they do not have stock on this particular part number and cannot give us an ETA at this time. Thank you Sincerely, The Wrench Monkey Team Quote Link to comment Share on other sites More sharing options...
Ken Smith Posted December 31, 2016 Author Share Posted December 31, 2016 Any pics of an aftermarket drier with the original hard lines and high pressure switch? Also, where you got the drier or make model info. I hate to buy one and have to return it if someone know what will work. Quote Link to comment Share on other sites More sharing options...
KimKarl Posted August 12, 2019 Share Posted August 12, 2019 On 12/31/2016 at 2:05 PM, Ken Smith said: Any pics of an aftermarket drier with the original hard lines and high pressure switch? Also, where you got the drier or make model info. I hate to buy one and have to return it if someone know what will work. Please if you have the part # of the replacement drier, and a pic of an aftermarket drier with the adaptations, IE: Original copper lines and high pressure switch port for 134A, it would be most appreciated. I do have the 134A retrofit 2 terminal switch and harness combo, part # MT4028 by Santech. Thank you for your kind consideration. Quote Link to comment Share on other sites More sharing options...
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