Hi, Last year my A/C started blowing warm (after about three years of blowing cold). It was converted (properly to R134a) years ago. After some troubleshooting today, here is what I found.... Some facts: Ambient outside temp. approx 75 deg F Compressor belt relatively new, correct tension. Fuse okay With A/C OFF, manifold gauge set attached: LOW side 23 psi, HIGH side 25psi With A/C ON: LOW and HIGH side readings remained unchanged. Sight glass appeared to be clear The compressor did not sound like it was engaging (or it is hard to hear with engine on?),used stethoscope - no change in sound coming from compressor, idle also not affected. So, sounds like compressor not enaging. I am wondering: What should the low side should read with the A/C disengaged and engaged? The GT4 manual states Low side should be 1-2 kg/cm2, which is approx. 14 - 28 psi with system running. If this is the case, my Low side pressure is normal. My high side pressure does not increase due to compressor not enaging. I am assuming 25 psi on the HIGH side is very low, even without A/C on? What should the HIGH side read without A/C on? - very high probability my low pressure cut-out switch is coming into play... Before I do anything else, i.e., evacuate system/recharge, I wanted to bounce this off you guys..... Curious to know what you guys think...... Thank You, Anthony
did you check to see if the clutch was engaging? could be a blown fuse for the clutch or else it may be low on freon. steve
Low pressure side needs to be between 25-45 psi. You will see air bubbles in the sight glass. 134A only requires 80% fill vs. R12 . The best way I have found to fill it is to put an AC therm. in the outlet duct and turn the system on full and when it reads 40-45 degrees you got it. So I suspect your compressor is not going on because of the low pressure switch . Go out to any local auto store and buy a couple cans of 134 with leak sealer in it and plug it in. My 2C
Thanks.... Steve....yes, thanks.....I want to evacuate system of moisture/check for leaks, before I recharge......hopefully, low charge is all it is.... Anthony
If u still have 25#s in system no need to evacuate as 25# still positive pressure & moisture/air can't get in. I'd say just add freon. Bill
I'm with Bill here. Just put another can of 134 in and get it to the right pressure then see if it lasts. If you start to loose the charge then you need to do some leak work. If the car is stored it will sometime loose some of the charge. Give it a try , 134 is cheap.
....Thanks, at this point, I tend to agree... Question, though: By now, I know some of the info given in the GT4 shop manual is inaccurate, but what about the low pressure specs that are stated? They are stated lower than the standard 35-45psi ranges for a low side of a system...I believe the 1-2 kg/cm2 that is given equates to 14-28psi.....?
Earlier posts are right on, Your system is holding pressure, last charge held up for several years, so you only have losses normal for a retrofitted system. Very slowly add a can of R135 until it brings the pressure up to where the compressor will start running. It'll cycle on & off at first, then come on & stay on. Once the compressor stays running, continue slowly adding coolant while monitoring vent temp as described. Add a little bit, then wait a couple of minuites for the system & thermometer to respond before adding more. When system first starts operating, it'll probably blow warm, then begin to cool down as you add more coolant. It's easy to go too fast & over-fill. The system will cool down to around 35-40 F, then start to rise as you add a bit more. Stop when it gets to ~45 F degrees. Pressure readings are very dependant on ambient temperature & having a lot of air at that temp blowing thru the condensor coil & radiator. Too complex to try to explain here. Go to the library & get a textbook on A/C service if you want to understand how to recharge by interpreting pressure readings. Don't trust the single pressure gauge a/c refill cans. They can badly misslead you. It's best to do the above with the temp between 75 & 85 degrees, with the car out of the sun. Otherwise the A/C may not be able to handle the heat load & you won't see the dip then rise you're looking for. Also, put the biggest fan you can find blowing into the front of the car. One of the big carpet drying fans works vy well. A box type floor fan will do in a pinch.
Thanks Verell....Yes, I have studied the Haynes techbook over the years and have a good set of manifold gauges, a 3 cfm vacuum pump I am familiar with proper gauge readings, charging etc... I have done this service to my "normal" car in the past, but I was just questioning the pressure readings given in the GT4 workshop manual, because when it comes to the 308, I want to REALLY be sure! : ) Thank you again for the help! Thank You, Anthony
The GT4 and 308 series cars have a very basic AC set up. The GT4 manual is not applicable for 134A conversion so you need to get the pressure charts for 134 and not R12. 134 runs at a higher pressure. It is not as efficent as R12 but more readily available and at lower cost. So just give it a shot and you're good to go.
Great! Far too many people just jump in with the gauged cans & haven't the foggiest what they're doing. You can find R134a tables on the web with a quick search. I've got my A/C stuff packed away, so can't give you the pressures I used on my 308. Think I was using a low side pressure corresponding to about 38 F to 40 F. I remember that on 308 york style systems I get the best cooling with a lower charge than my R134a chart & system capacity indicated. While I use the gauges, I also use the procedure I described to fine tune the cooling capacity. Watch the high side pressure carefully, if you overcharge w/R134a it will head thru the ceiling. Also, be careful when hooking up the gauge fittings if they were converted to the R134a style fittings. It seems like it's much easier to damage the little pin that actuates the shrader valve inside the R134a fittings than on the old style fittings. Then it's a real PITA to get the valve core out with the center pin bent over(been there).
Thanks again, everyone! Verell, thank you!....I am too much of an engineer......have to know exactly what is going on and ask lots of questions! : ) Anthony
I'm an engineer also, drives my wife nuts when I try to analyze why a supper dish did/didn't come out great...
They readings are equal because the compressor is not pumping. A fully charged system should read 35 -40 lbs. on the low side ac on. One other note. I have found 134 to have a service life. 3yrs is not bad for a recharge needed. Sounds like you have had normal leakage.
I'm to the point that I am taking out my old compressor, any tips on the removal? There seems to be a coolant pipe in the way and I think I have take off the alternator belt and A/C belt. What do you guys think? Can I take it out without removing the coolant pipe? Am I on the right track? Should I take it out through the side wheel well or up top? What would be easier? FYI - I posted this in another thread as well to double my chances at finding an answer, so sorry for the duplication! Thanks! Dom
Excuse my ignorance regarding the following questions, but a/c systems are one of the few car areas that I have no experience on, being European is the main reason, we are newcomers to this luxury ! Anyway, my 328 is not getting cool air, the pump solenoid seems to engage and my presumption is my system needs re-charging, my first dumb question is how do I know if my system uses R134 or the old Freon ? any other basic tips that will help me track down the problem ? I do have one of the supermarket type a/c gages which is pretty new so I presume is intended for R134.
Dom, Yes, you might need to remove the coolant pipe. I can't remember if you can get the A/C compressor out without removing it, but you do need to remove it to service the belts, which requires removal of the pipe. You do need to remove the alt belt. Just loosen the adjuster on the alternator to gain some slack and you can pop the belt off easily. Birdman
The size/type of the (service) fittings at the suction and discharge ports on the compressor are how to identify which refrigerant is in the system -- I'm sure that you can find the fitting details for each with an internet search. If your compressor is engaging, have a look at the sight glass on the dryer when in operation -- if you can't see "flow", the system has lost it's refrigerant (or some other horrible thing, but failing the "sight" test means that you're up to the point where the high and low pressure behaviors are needed for more diagnosis or refilling anyway). PS Absolutely nothing "special" about the 308 AC system -- any (even non-F) competent AC shop should be able to diagnose/fix (if none of the big parts need replacing).
Are the fill connections fool proof ? meaning that it is not possible to put R134 in a R12 filled system ?
The R134a & R12 fittings are very distinctive, you can't mix them up. R134a fittings are a quick disconnect type, R12 fittings are threaded fittings very similar to plumbing 'flare' fittings. Also, there's suipposed to be a refrigerant label in the engine compartment giving refrigerant type & weight to charge the system. The only caveat is that once in a while some amateur will convert an R12 system to R134a w/o installing the R134a fittings or putting the EPA mandated R134a lable in the engine compartment.
Hi, Okay here is what transpired and my NEW PROBLEM! ...well today I slowly started filling my system while monitoring with manifold gauges. The system did have some initial pressure (20psi on Low side) as indicated in my initial post, and the compressor was not engaging due to low refrigerant charge. I added 134a from a can very slowly....the compressor kicked on and dash vent temp. started decreasing from approx. 80 deg F (temp outside) to about 70 degrees......the low side pressure was still not up to where is should be (it was about 28 psi, HIGH about 120 psi). Sight glass went from empty to steady stream of bubbles - so far so good.... BUT, I encountered a problem that was not as pronounced in other vehicles that I have charged with a can: The can would only empty half way, i.e. as refrigerant went into the system and the can lost pressure, the can's pressure became too low to sustain refrigerant flow (or flow very slowly). I kept the tap on the half-full can and sealed it - used another tap on a new can, refrigerant flowed again until can only half-empty - Low pressure then read 32 psi/high 150 psi - dash vent temp. about 60 deg - sight glass has stream of bubbles, but as expected, less than before. Now, I have two cans I have to dispose of properly and I still need to put more in the a/c system. When I did other cars in the past, the cans seemed to almost completely empty when refrigerant was needed. I did not heat the bottom of the cans, but maybe I should have.....any advice or experience with this problem? Oh, by the way, last year when I purchased a 12oz can of R134, it was less than $4. Now, the price (at every auto parts store I checked) is over $10 and rising! Seems r134 is heading towards the r12 route..... Thanks, Anthony
As you sucked coolant out of the cans, the coolant remaining in the can cooled down until it was below it's boiling point. Just set the can into a container of hot water & let it heat up for a few minuites, & continue filling with the can in the water. If it stops flowing, let it sit a few minuites to warm up the can's contents. Repeat as necessary to empty the can.
Thanks Verell...... When I unhooked the can from the manifold, then cracked the tap value (for less than a second), gas would flow out freely (with what seemed like a higher pressure than the low presure side), that's why I did not think that I had to warm the can initially.....yes, a temp increase would do the trick............ Thank You (again), Anthony
I think you have air in your system. I had to recharge my Lotus Esprit on Saturday. This is what I did. 1. Installed 134A adapters on Low side (Suction Side of Compressor) and high side (Discharge). Connected low side and High Side lines. Fill line connected to Vacum Pump. Ran on Vacum pump for 2 hours. Pulled 25hg of Vacum. This is a very important step - few home mechanics do. This pulls all moisture out of the system and most importantly the receiver dryer. 2. Closed lines off to maintain vacum. Connected 134a Cyl. Started car and turned on AC. Opened control valve on line to slowly add freon to system while watching gauges. Keep in mind while filling low side will jump to 70 -80 lbs while filling. Stop filling and watch the low side gauge come down when gauge remains steady at 35 - 40 1bs. the system is full. Hope this helps. Some things to consider is almost all systems have air in them it is so important to get the air out and create vacum. Also I have found that my Ferraris and other midengined cars require 4 -5 lbs of Freon. Another note regarding AC parts most everything on a Ferrari is very Generic. It is easy to get parts for the system from local parts suppliers. Regarding prices of 134a. The rumor is that the Dupont plant was shut down by the EPA. This means no production for 6 - 12 months. I personally have stocked up on 7 30lbs cylinders for the dealership at a cost of $299 per cyl. (Yikes). They say it is going to $700 per cyl. R12 is Currently $750. What a scam.
