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1990 Nissan Hardbody hot air

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    1990 Nissan Hardbody hot air

    I know this truck is old but I bought it new and it still runs great with well over 250,000 miles on it.

    About 10 years ago the AC give me problems similar to what I have now. I replaced the expansion valve and drier, put the R12 back in it and all was well until a few days ago. Yesterday the vent temps were in the 70's. .

    I connected my gauges and the low side will go south when I give it the gas and the high side goes to 250 #'s. The low goes from around 30 psi at idle to half that when giving raising the rpm's . It is also hot and humid where I live.

    This morning I got in the truck after sitting overnight I noticed the temp was at 40 degree and it was working fine. When I got back home the vent temp was around 50 and going up.

    I again connected the gauges and same reading. It starts blowing hot air. At idle the gauges read 200 on the high side and 30 on the low side at idle but no cold air. I accelerate and the high goes to a little over 250 and low back down to around 15.

    Am I looking at expansion valve problems again ? I know I lost a little Freon when I connected the gauges and caught it before too much got out. It is showing air in site glass on the drier now but I don't have but one can of R 12 left and don't have a recovery machine. I think I can get enough R12 from a friend who does ac work.. He told me last month he has a 30 pound can of this.

    I don't really want to convert it to 134 because when I used to mechanic years ago I did this type thing and never got the vehicles to cool as good as using R12.
    The compressor seems to working fine and is nice and quite. It will cut off when the high side goes above 260 plus or minus and few PSI's. but kicks back on when it drops back to around 200 psi.
    Any tips will help. I still love to drive this old truck even though I just bought a new Toyota Tacoma TRD sport

    How hot is the outlet of the condenser? Pressure tells me 155-160 deg F which is way too hot. If the outlet measures that hot, then replace the condenser, if not then look at a restriction. Feel the whole system with your hands and try and find somewhere the temp drops where it shoudn't. Your thinking it could be a Tx valve is good, but that isn't the only thing that would give reading like you have. Any restriction will cause the high side to go up and the low side to go down.
    When it is blowing hot you can try misting the condenser with water and see if the pressure goes down along with the vent temp. If so that is another indication of a bad condenser.
    How is the engine fan, does it have a clutch and if so is it working? Poor air flow over the condenser will give the exact same results as a bad condenser.
    Depending on what part of the country you live in, a condenser is the most likely culprit. The de-icer they spray on roads now a days loves to get in and corrode the joint between tube and fin so no heat from the tube gets transferred to the fin, so very little heat get removed at the condenser and it re cycles back to the evaporator.


      Welcome. Wow and all OK that it's old - still R-12 think calls for 32oz of the liquid gold. Things to check before another X valve job and trouble to save what you have understood. Nobody but bone yards are maintaining anything to recover that anymore if anything goes wrong - forget it.

      So, pressure too high and lousy performance? At a glance and do list what ambient temp you are working with the condenser can't throw off the heat. Probably feels quite hot or should at about 150F temp of it where checked.

      How is the fan power and how done - fan clutch or what? You should plain feel the hot air blowing off condenser and radiator quite well with hood open. Try cooling condenser with first misting with water and test really dousing it while watching pressures and vent outputs with a raised idle. If that dramatically lowers vent output temp condenser needs cleaning up - bugs - dirt and or leaves in between it and radiator too have to look.

      You may be low just from the screw fittings have to be fast as you must know owning it so long. A trick for that is use retrofit quick connect adaptors and then gauges for 134a but grease the threads (they come with thread locker) so you can take them off so no confusion what's in it. Check now if they are leaking. Good old soapy water if Schraders are holding well and should. If leaking use the tool unscrew a bit and just snug up a couple times if needed leak should quit. Tools to replace them if the problem run into bucks while not losing refrigerant.

      Caps? IDK where to get great new ones. Maybe brass and fit an "O" ring in those if yours have had it and see what fits for an "O" ring preferably a flatter one.

      Jeez - even tires these mess up with age.

      In short I think it's both low and probably not enough airflow thru it for now. Check for these things first and see if we can save the Freon which it is.

      On that I heard of a trick with dry ice and an empty 30lb bottle you can save most of it! Never tried that but would start with a totally evacuated (full vacuum) on 30lb tank and freeze it cold does sound like it could work?

      See what you find with those check and tests,

      MetroWest, Boston


        Same thinking Cornbinder89! Don't see another posting at the same time,
        MetroWest, Boston


          I might have caused some of the no cooling problem today when I connected my old gauges. It was leaking and I didn't see or hear it. I don't think I lost much but the site glass is showing it is low. I know this morning it got to 40 degrees when I first drove the truck as I kept the thermometer in the vents.

          I was also checking what you posted about head pressure. When I mist the condenser the pressure will go down to around 150 from 250 fast. Being I am now low on Freon it will not cool like it did early today Nobody has ever touched this truck so only R 12 has ever been added.

          I bought it new in June of 1990 and like I mentioned it has been at least 10 years since I last worked on the AC, maybe more because time gets away fast

          I did noticed two weeks ago when I drove this truck on a 50 mile trip it was blowing mist out the vents like it had froze up. It stopped cooling also so I just shut on the AC. Same thing on the way back. Cooled for the first few miles and then mist coming out and stopped blowing cold air.

          This morning it was cold but not now. I also noticed the high pressure line may be leaking coming from the compressor to condenser when I was checking it late today. I think maybe the clutch fan is bad but over all my years working on vehicles I never knew a sure way to test this other than just replacing it. I am sure it would not be a waste on a 27 year old truck.

          I had the truck painted three years ago and it has new tires on it so I hate to junk it but here in the deep south I don't want to ride in a truck without AC. To old for that I hate to add any Freon in it now being I see oil around that hose. This old truck looks and rides great so I got to make up my mind if I want to invest any more money in it being I have a new Toyota.

          I used my infrared thermometer on the high pressure line coming from compressor , it showed 225 degrees. Where it goes into condenser about 160 degrees.

          I looked in my workshop and did find one can of Johnsen's Freeze 12 and I am not sure about using this. A person give me this can years ago and it has been sitting since that time.

          If I can get the friend to add a few ozs of the R12 tomorrow to this system that I lost today I will then see if it will cool when I mist the condenser. If so then I will order the line and clutch fan.

          I will update you on what I find. Tom


            Last month I discovered my 1998 Frontier truck had a bad fan clutch, saw that visually and confirmed with the "rolled up newspaper" test, see Google for that; it was 4 years old. On my 1988 Mazda truck, seems like my Hayden fan clutch (was lifetime warranty when I bought it) seems to last about 6 years. Yes, I'm in Arizona.

            Originally posted by Tom Greenleaf View Post
            On that I heard of a trick with dry ice and an empty 30lb bottle you can save most of it! Never tried that but would start with a totally evacuated (full vacuum) on 30lb tank and freeze it cold does sound like it could work?
            I've recovered R-12 using a smaller canister with a shut off valve with a 1/4 inch flare connector no longer used at work (originally contained hydrogen-nitrogen mixture). I pulled good vacuum, shut off the valve, cooled it in a dry ice - used engine coolant bath, connected to my service gauge kit (bled a little) and let the R-12 get sucked over by the vacuum where it condensed so still had vacuum in the canister, the R-12 continued coming over. My canister holds like 32 oz. R-12, so a good size.


              Sixputt: Freeze 12 is another whole different product catching the name makes you think it's about anything R-12 - it isn't! Different totally don't mix that in and I don't care for it at all.

              You do have a sight glass so that removes most doubt on charge. Use it and know you are low. All other discussion on saving what you have is probably worth the effort. It would convert over to 134a but getting old to make it work real well again.

              Clutch - all cleaned up I say go ahead and boost it back up via sight glass.

              Look for more R-12 if you have some more years with this. Little cans were usually 14oz will say the chemical name - read it off containers for air horns (once coast guard kits for boating, horns for just any reason too) are still out there so can be side tapped. There's no shortage, it's just a pest to find new stuff. Good luck,
              MetroWest, Boston


                I found one can of the R12 today from a friend who still works on cars and trucks. I give him $10 which was great

                Now to find some more in case I have to break this system open . I may try and recover it the way you mentioned. Don't have a clue where to buy dry ice ? but I do remember it.

                It was the 12 oz can as that's all I ever remember buying and believe me I bought many cans of this back in the 70's and 80's . Seems like it below 50 cents a can back then ? I remember Freon so cheap in the early 70's I would use a can to make a warm 6 pack cold wonder how much money went up in the ozone back then lol if I had saved it .

                I also tried the test on the clutch fan. I found a piece of thin cardboard and folded it up like you mentioned on the newspaper. I did stop the fan after it was running long enough to get hot. I actually though about checking it this say way when it cools just to see if this test really works. Never heard of this one until I read here.

                It has been over 20 years since I last worked on vehicles so hang it with me if I sound stupid

                I actually still have my card ( MACS) dated June of 1993 here at my house. I remember when all this stuff started going sky high but did not buy enough to last me as my friends got most of it after I retired from the garage business in 1997.

                This old can I found today will have to be side tapped as it is rusty and I am sure my can cutter will leak if I try and use it. I once had a side cutter but don't remember where it is now. Maybe still in my shop that was closed in 97 with all the other American Picker stuff that's in it also

                I also didn't plan on using the Freeze 12 in my Nissan. I only want the original stuff which was R 12. I may just give it to a man who is also a friend of mine that's still in the business and he can do what he wants with it.

                I drink coffee with a man a few days a month who was in the heating and air business ( commercial ) for 40 years and he looked at my truck this morning after I connected the old gauges. He seems to think the system is plugged up somewhere like mentioned here. I give it the gas and the high side went to 250 fast and low went to 15 and the truck had been sitting for about an hour plus The discharge line was really hot, so hot it would cause a bad burn if touched. I checked this morning just lightly touching it and around the drier it is not as hot as the line going to condenser from compressor. I know they get hot but I never remember checking to see how hot in years past.


                  When it is blowing hot you can try misting the condenser with water and see if the pressure goes down along with the vent temp. If so that is another indication of a bad condenser was a suggestion of Cornbinder89. I did that. The pressure dropped but not the vent temperature.

                  Maybe because I lost some Freon yesterday when checking and didn't catch it until too late. This R12 is gold so I got to decide if I want to top it off with the can I found today or wait until I know for sure whats happening with it. I know for sure its a little low but not sure low enough make it just blow hot air . Back to the drawing board lol


                    Update. I took my infrared thermometer and shot it across the condenser taking my time at each area. I think maybe I found a blockage

                    One place on the top row will get to 140 degrees and I move the red dot about two inches and it shows 88 degrees. Most all the other places on the condenser shows 75 to 88 degrees except that one spot and I checked more than once. I could not get to all the places on the bottom until I remove the grill but that one place shows me there is a problem.

                    It seems to be one spot that is blocked. I do think you are correct that the condenser is trash.

                    Now what plugged it up could have came from compressor, I am not sure on that one. Maybe age related.

                    I just never thought much about a condenser being the cause but I took my time and shot the infrared all across this thing and that one place stands out.

                    Thanks for the suggestion on this. Now I got to decide if I want to put this much money in a truck this old
                    Last edited by sixputt; 08-07-2017, 09:03 PM.


                      If it were me, and I had to change the condenser, I would fit the biggest (capacity) generic parallel flow I could fit, and go back with 134a. If you increase the capacity of the condenser 30% you all but eliminate the "penalty" of 134a. I would also change the fan clutch while I was in there, as you have proved that yours in no good.
                      Did this on the truck I am in right now, and it has the best A/C of anything I ever had. I get a hint of frost on the outlet of the condenser with temps upper 90's to 100. It is an '83 so R12 from the get go. Never thought I could get it this good on 134a.


                        Would I have to change the oil in system if I go with 134 ? I am all for doing this as R12 as become way to high in price. I have two cases of 134 I bought when on sale for $3.99 a can so no problem on Freon. I know I also need a high pressure line because I can see oil on it. Where would I find a condenser like you mentioned ? Thanks


                          Some notes on all this: It's old (said so what) and parts may be an issue. Now seem to have found a blockage my concern is WHY as the OE condenser has large passages so knowing why it's blocked would be important to me. Compressors that fail or are failing do that so it would probably just do it again quickly if source issue isn't fixed.

                          Oil? You decide based on which refrigerant you want to go with the oil must change. I would choose Ester for 134a if you do that. Not sure why but it claims to be compatible with the mineral oil used in R-12 to me now back when lasted the rest of the life of the vehicle which isn't long here if you drive all year round your vehicle will hopelessly rust out - almost no exceptions to that - never mind A/C the frame will fall off.

                          I did find as discussed on the old forum still archived above that old good rubber hoses didn't leak with 134a which otherwise would require "barrier" hose and O rings/gaskets of OE rubber replaced.

                          Also know your sight glass would no longer be a valid visual indicator of a correct charge.

                          There's no problem if you change out condenser as Cornbinder89 said you would have about the same cooling as R-12, a known good fan clutch or new one that is thermostatic would be right for any and better for plain cooling the engine - on this layout your temp gauge should not vary once warmed up ever IMO. If it does fan and or radiator for engine sometimes water pump impellers give up unseen is critical - no engine no A/C no matter what you do.

                          You can have a problem with A/C if engine runs too hot with radiant heat backwards towards condensers,
                          MetroWest, Boston


                            I'm going to go out on a limb here and say your condenser is not blocked, My reasoning for this is: you say the inlet to the condenser is HOT while the receiver is not quite as hot, but you IR temp readings show a condenser temp (execpt at the 1st little bit) of 77-80 deg. If it had a restriction, you would expect the receiver to be the same temp as the rest of the condenser.
                            What I think is the thermal bond between the tubes and fins is bad, and there is no blockage, but also little to no heat transfer also. Either way the condenser has to come out, and when out you can check for blockage before proceeding further.


                              Tom, I am not 100 % sure that the condenser is blocked. Using the infrared may not be the proper way to test. I do find it hard to believe it is stopped up on the inside.

                              I just had it and thought it might work ? I bought it after I retired to test a blocked catalytic convertor on the Nissan Xterra I acquired from my son after his wife blew the engine. That was my first retirement job rebuilding the engine on a 3.3 at the age of 65. That was 5 years ago and no way am I able to do something like that again. Age has a way of working on one's body

                              On the old Nissan truck with AC problems. ~
                              These were pretty solid trucks but when I do see one today normally the windows are down meaning someone else had these problems and didn't want to spend the money required to repair the AC.

                              This is just a truck I bought new and have always took great care of. It is old with lots of miles. I am not even going to replace the engine if it goes south, well I say I will not I paid $9000 cash for this truck in June of 1990, It didn't even have a rear bumper on it and also no radio. Just a basic truck that has give me many years worth of use. I replaced one fuel injector on it about 18 years ago because it started skipping one morning.

                              I replaced the muffler and tail pipe way back when. I also did the timing chain in 1999 and not 100 % it needed that done. These engines just rattle when first started up. Not long after I bought it I started hearing that noise and today it still makes it. I just live with it. I have tried OEM oil filters to stop this and even added a little more oil to engine. I found if I park it backward in my drive way it is not that bad. My driveway has about a 30 degree incline. Something about the oil draining out of filter after sitting overnight. Oh well enough of all that

                              Last year was the first time I even put rear brakes on it. The ex valve was the only AC problem I ever had and I think Nacho helped me on this when I was a member of the old forum . Is he still around ? He was the best AC man I ever run into over my 70 years.


                                Originally posted by sixputt View Post
                                Don't have a clue where to buy dry ice ?
                                Some grocery stores sell it by the pound; ask them.

                                Originally posted by sixputt View Post
                                I also tried the test on the clutch fan. I found a piece of thin cardboard and folded it up like you mentioned on the newspaper. I did stop the fan after it was running long enough to get hot.
                                Replace the fan clutch.

                                At 221K, my 1998 Frontier AC has had R134a added once (by me) and got a pinhole in the high side hose a few months ago (accelerated possibly by high pressures from its bad fan clutch). Its AC works great in Arizona heat too.


                                  Ditto on replace the clutch just anyway. Many lose it in 5 years. Once a choice of a type that seemed to just stay at 80% (a guess) of speed of belt hot or cold works real well but annoyingly noisy/busy sound all the time.

                                  Infrared for a condenser with engine running and any air blowing around results will be awful hard to count on. Essentially doesn't matter how you cool condenser the "in" temp has to leave markedly cooler no matter how you do it and noted the water worked does suggest no complete blockage and a partial might get cold right there if tube and fin never saw one just block up.

                                  Also note by my location a real truck of any sort around this year or older never came with A/C it was to work with - any toys didn't make any sense. Usually seeking out load ability.

                                  Not many "plain" pick-up trucks around new anymore at all full of toys, 4dr ones everywhere now too. Haven't seen any now w/o A/C a total switch,
                                  MetroWest, Boston


                                    I put the clutch fan on today and also added the one 12 oz can of R12 to the truck. The site glass finally cleared up.

                                    I watched my pressure reading and the high side shot up to 250 pretty quick. I held the throttle down for a good while but could never get the vent temp to come up 70 or the high side to drop below 240. When I was first connecting the low side to charge the system I did notice a large amount of oil coming out so I just let some more out. This system may have had too much oil in it from the last time I worked on it and that was years ago. . Maybe large amounts of oil was what was stopping this system from working ?

                                    Anyway I was watching the pressure while holding the throttle to around 2000 RPM's. The high side stayed high for some time and then all of sudden I noticed it begin to fall. Now this is 40 minutes after I put the Freon in. Don't know why but it begin to cool. I had the vents on low and watched as it dropped to 40 degrees and pressures were fine. On the way to my house the temps were between 40 and 50. I can live with that as it was a very humid day here but the sun never showed up. I also know it had to be working good because of all the water that came out of drain tube.

                                    I don't have a clue what made it start working correct. Same thing I had before I installed the clutch fan and freon but like I said it did finally start to work. I don't know how long but for now I am leaving it be. THANKS for the help on this.


                                      A wet system can give you fits, as ice forms then melts the pressures can go all over the map. Kinda sounds like what is happening. Either that or the Tx valve was stuck and then freed itself.


                                        Wow - 40 minutes and seem now it just working I might also say Tx valve snapped to on it's own.

                                        The new fan clutch may also be very old stock and have oil in it. Those should be stored in box setting as it would in the vehicle or some would say or have arrows at least face/front down not the other way or they don't work properly or worse those leak out oil. There's a chance it took a while to get used to itself?

                                        The oil thought overcharged? I doubt that's overcharged for years on end without some symptoms if so. If you are going to hook up for pressure checks or any reason I suggest putting a quick connect on that port - some fussy threaded ports by location and condition hose and fitting take too long in that zone of leaking before sealed tight or back off - not too much of that or mess up how much you lost and knowing it.

                                        If ice is happening as Cornbinder89 mentioned it could in some situations but notice slowly lower air volume out vents and when stopped or shut down a huge puddle of water not just normal condensate (water too) can all be telling or observed and does make things erratic.

                                        This is exposed to very high humidity obviously a lot of the time. It doesn't stay that humid where I am very long or often but does.

                                        Interesting site for you altitude, weather forecast, current weather observed local to you I use lot is also handy. It's here but may be blank waiting for you to put in a zip code for yourself or the closest you want to where working on this or just anyway..........

                                        > http://www.intellicast.com/Local/Wea...ation=USMA0235 <

                                        Check that out - live radar there also. Good info along with your own devices I find very helpful. Good luck with this truck and think there's isn't too much more I would do right now while working with a sight glass showing good would stop messing with it just leave thermos in a vent you can glance at now and then when using it,
                                        MetroWest, Boston