Does anyone have experience in changing out the expansion valve on their Mondial QV (84) While the evap. unit is still in the car? can it be changed without removing the dash? I believe my valve is stuck or the filter within the valve is blocked. low side pressures very high 50,and high side pressure very high 400 after only 2/3 fill of R-12. I changed out the compressor, Freon lines, drier, and a flush of the entire system previously to prepare for the recharge of the system. Vacuum pulled the system for 1 hr. held pressure for more then 2 hours before I started the refill of the R-12. any thoughts or insight is greatly appreciated
There is a flush procedure somewhere on the forum (not sure if it is in the 456/550 section or 348/355 section) about flushing out to resuscitate a partially clogged expansion valve. It sound like have already done it, but it would some pretty stiff blockage if you flushed and you are seeing 400 high side pressures! (I assume your condenser fan is running....). I don't know that I have ever seen an expansion valve completely blocked. Do a search if you think that might help. The author swears he has never had to change an expansion valve. Here are two possibilities: From fatbillybob Here is a related post from ferrarioldman: If you do pull the expansion valve, just try to match it up. Porphy had good luck on his recent thread doing it on his t, not sure if it will be the same as yours. Regards, Jerry
thanks Jerry, good info. I just removed the left, front wheel and gravel guard, the cond. fan is not running, I tried to jump it to see if it would turn, it does not. "are seeing 400 high side pressures! (I assume your condenser fan is running"....). This morning after letting the car settle a bit overnight, the a/c "seemed to be somewhat functioning, it is 95 degrees here and the thermometer in the vent is showing 60 degrees. the low pressure is now at about 20 being, I never finished the complete filling due the high indicated pressures. will a non-functioning condenser fan cause some these issues? I didn't flush the low pressure side because the directions, and everything I have read said to never flush the expansion valve as it could cause particles to lodge in the orifice, always remove first, I did blow some compressed air through the evap. and low pressure hose back to the compression, no issues, so it seems the only likely blockage, if there is one would be at the expansion valve/screen, unless the condenser fan not turn causes a similar issue? Again thanks for your assistance! Mark
Mark With no condenser fan at idle, your high side pressures will shoot up. The compressor should shut itself down if the pressures are too high, which will explain why no cold air. Before you work on the AC, I would recommend you get the fan running. If not, then get out on the highway where the moving air will be sufficient and see how the AC works. Even if you are off, you should get some cold air. Remember, too much Freon can be worse than not enough. THEN, after you get the fan working, you can put some manifold gauges on it and check your pressures. 20 on the low side is probably not enough R12 (which is pretty expensive these days), but you need to watch the high side. As a rule of thumb, use about 2x ambient plus 40-50. So if 90 degrees, that would be 220-230. As to flushing I have had it done many times, I see nothing wrong with it. But I am no expert. After flushing, do a good vacuum to get out all the air and all the moisture. Make sure it holds vacuum. Plenty of good youtube info on that. If you are using the original R12, somewhere there should be a label or info in the OM about how much to put in. Don't forget to add a small amount of proper oil if you vacuumed out the system. Regards, Jerry
Jerry is correct in that an inop condenser fan will cause high pressure side to climb. It can/will climb to the point of offgassing via popoff valve because very few R12 systems have a high pressure cutoff switch. Just a low cut. R12 is a beautifully forgiving refrigerant because it isn't grossly affected by over or under charging (within reason now) Still makes cold! 134, on the other hand, is very finicky, especially in a conversion....of which I have done many. Get the fans replaced, even if a generic from Oreilly/etc and see how she does and let us know. New multi bladed unit will probably be quieter! Lol
O.K. got the fan repaired. It did in fact bring all the pressures down HOWEVER, after running the compressor for a few minutes to see if there was a temp reduction, I noticed the low pressure side went into vacuum and the high pressure side pressures went way down. From what I am reading this is a good indication of an expansion valve is stuck closed, maybe the inlet screen is clogged? Your thoughts? Please?
Again, I am no expert, but I would say there is a blockage somewhere. Most likely candidate is the expansion valve. The low side "sucks", the high side "pushes". The expansion valve opens and closes to get an equilibrium based on temperature requirements. At least that is how I understand it. Do pressures stabilize after you shut the car off? Regards, Jerry
No that's the strange part. when I turn the motor off all the gauge readings climb, probably due to heat? the static pressure is/was very high for both, when I restarted the car and turn the a/c on, the pressures never dropped from the static pressure and actually rose a bit. the compressor wouldn't turn on due to the pressure switch cutting the signal to the compressor off, correct? All I can now figure is there is a solid blockage most likely in the expansion valve area as that was the only place I couldn't/didn't flush. The Mondial is equipped with a filter screen in the exp. valve maybe the PO had the drier go bad and the sand like material went through the system and blocked the valve, maybe even causing the compressor to seize in the first place. Am I reading to much into this? To recap, I have changed the compressor, the drier, the low pressure hose, the condenser fan, all were defective. The system held vacuum extremely well , I did flush the high side from the drier back to the compressor through the condenser, got a small amount of rust flakes from that flush out of the hose, dye checked no leaks, (good vacuum) The system never did seem to equalize pressure when both manifold gauges were on during brief first fill of Freon (5 oz's) with the motor off. After the condenser fan was fixed I finally noticed the other end of the drier hose that went to the evap. was cold and sweating, bit no cold air being produced and low pressure hose at the compressor was not cold. Sorry for the long winded recap, your help has been keen on troubleshooting this system that so far has shown nearly every part had an issue, ( 31 years old) had to start somewhere and eliminate each fault. Thanks, Mark, sweating in MS.
You might be able to replace the expansion valve without removing the dash. You need to get under the dash and try to find the bottom of the "black box" and the pop-rivets that hold the collector of the condensation and routes the condensation to the tubes leading it through the firewall to the outside. This collector will need to be removed. Drill out the pop-rivets and pull the collector away from the bottom of the "black box". You will need to remove the metal cover which covers the heater control valve. When that cover is removed you should see the tube from the filter dryer which crosses the firewall and then goes directly to the expansion valve located on the right-hand side of the black box which is accessible after the condensation collector is removed. Sorry about this long description but if you will start this and send me pics I can probably talk you through it as I have removed my black box and replaced the expansion valve recently among other replacements. My only fear is that I have a "T" and there may be minor differences between your car and mine. I cannot imagine that the expansion valve is different. I did find dirt in my expansion valve filter however. The replacement expansion valve had no filter even though I removed the old one, cleaned it and installed it in the new valve. Good luck Mark. Randy
Thanks Randy, and GSFENT, for your help, and your initial posts showing your progress with the Heater box removal, it was my inspiration to tackle the A/C. I think I will put the car back together for a short time in order to attend some car events, now that I think I have it figured out, I can always put the top down. When I get back at it I will post some photos. Just another example of why to not believe a seller who swears the A/C just needs to be recharged!! HA! if nothing else I have learned much about the 80's A/C system workings and now have the equipment to help others in my area with their cars. Thanks again for your time, talk with you soon. Mark
If your pressures are low, just add more refrigerant and see what happens. Pressures will always equalize once system is turned off.
I had the expansion valve replaced on my 3.2 only to have the compressor go bad about a year later. Fearing another EV replacement I started researching other possibilities... From what I learned, back-flushing is what I was leaning towards; endorsed by a couple of pros as well. Also, I posed this technique to a highly regarded 80's Ferrari expert and he said "we've had some good success with back-flushing..." So, something to consider and it seems to be a common practice.
Also, as Randall suggested, there are some differences between the a/c "black box" of the t and previous models. But the EV itself is the same. Here's a photo of my ex during it's EV replacement procedure. . Image Unavailable, Please Login
A/C system diagnosis can be dicey. 1. The Mondial condenser fan has a temperature controlled switch (thermal bimetal) attached to the smaller/discharge refrigerant line coming out of the condenser coil that turns the condenser fan on, when the refrigerant line reaches a certain temperature. Make sure there is 12v electrical to one side of the switch with the ignition key turned to the run position and A/C main switch turned on. Or, jumper the two leads on the switch and make sure the fan will run with the ignition and A/C switches tuned to the on position. Failure of the condenser fan to run properly will cause high system (suction and discharge) pressures. 2. If both pressures are higher than normal, it is generally not an indication of a clogged or closed non-operating TXV (thermostatic expansion valve). A clogged valve, closed TXV, or clogged filter will normally cause a high discharge pressure and a low suction pressure. 3. There is a filter-drier canister/conatiner under the front hood on the right side of the car. It should have a high pressure switch and a very small sight glass on the top between the refrigerant line connections. With the system running and properly charged there should not be refrigerant bubbles in the sight glass. If the sight glass is clear there should be sufficient refrigerant in the system to function properly, for the current/ambient operating temperatures, inside the car and outside the car. 4. When the system is shut off after running, the suction pressure should rise, and the discharge pressure should decrease until the two pressures are equal. The static equalized pressure will depend on the overall ambient temperature of the system. That ambient pressure can be determined from a temperature pressure chart for R12, or whatever refrigerant is in the system. A temperature pressure chart can be found on the internet. http://www.foxmacon.com/Tecumseh/Temperature%20Pressure%20Chart.PDF 5. I think it would be more likely that the filter-drier is clogged rather than TXV. I am not are there is an actual filter in the Mondial TXV. A new "substitute" filter drier can be easily purchased from an A/C supply. 6. A quick check of the proper functioning of a TXV can be made by putting a hot rag on the TXV control bulb that is attached to the evaporator suction line. The bulb is connected to the suction line with a metal band/strap clamp. It may/should be covered with black insulation tape It is located under the dash on the top of the A/C box on the right side, but is accessible without removing anything from the dash or A/C box area. The hot rag will cause the TXV to open and allow more refrigerant to pass through the valve. Both pressures should rise accordingly. The hot rag causes the TXV to open allowing more refrigerant into the evaporator. Then put a cold rag on the TXV. This will close the valve, reduce the amount of refrigerant into the evaporator, and the pressures should lower accordingly. 7. For trouble shooting the A/C system it may work better to jumper the condenser fan control temperature switch on the condenser discharge line so the condenser fan will run continuously while the system A/C system functioning is being diagnosed. 8. Note that the temperature pressure chart only applies when the system is not running. 9. The compressor condition/efficiency/capacity and rotation speed, evaporator air temperature, evaporator refrigerant temperature, condenser air temperature, and condenser refrigerant temperature, will determine the operational system pressures while the system is running. Some may argue the opposite is true, too. That is, the pressures affect the temperatures, which is also true. 10. A properly charged system and a properly functioning TXV is responding to, and controlling, the indoor (inside the car) temperature, within the operational limits of the total system and the TXV. Good luck, Jerry Webber
Thanks much Jerry. Very nice information. I did, however, find a screen filter inside my TXV in my "T". It was dirty but not blocked. Is the temperature response of the TXV inherant in the design of the TXV? Are they more or less all the same.
Yes. The design of the TXV is a merely a valve that is controlled by the temperature (heat) of the TXV control bulb. You could use a manual type valve that is adjusted externally by hand to control the amount or refrigerant that is released into the evaporator, it would just be very inefficient to control. The TXV bulb it is the metal container at the end of the little metal tube coming out of the head of the TXV. The gas in the bulb expands or contracts depending on the temperature (based on the amount of heat absorbed from the air going over the evaporator coil) of the suction line coming out of the evaporator coil. The gas in the bulb system merely pushes on a diaphragm that pushes on the TXV control rod that opens or closes the valve port. When the bulb gets hotter the TXV opens to let more refrigerant into the evaporator coil. When the suction line gets cooler the valve closes to reduce the amount of refrigerant. The refrigerant should be a liquid when it goes through the valve port. As long as there is liquid refrigerant at the expansion valve the A/C system should work on that part of the system. The problem arises when the compressor and condenser can't condense enough refrigerant into a liquid to supply liquid at the TXV. The liquid refrigerant absorbs heat from the air inside the car that is moving over(through) the evaporator coil because of the evaporator fan. The air becomes cooler as the heat in the air is absorbed by the refrigerant. The fan then blows the cooled air into the car. Some A/C systems just use an orifice that operates to let a certain amount of refrigerant into the evaporator coil. The orifice is sized to operate across a narrow temperature range. The TXV type A/C system will operate over a very wide temperature range. Because R12 and R134 have fairly close thermodynamic characteristics, a typical TXV will work for either R12 or R134. The TXV bulb will compensate for the small difference in heat absorption of the two refrigerants. R12 has a little better cooling capacity, but R134 is more available and less expensive at this time. It is possible that a TXV could get clogged somehow, but more likely that the TXV control bulb gets a leak and then the TXV cannot control the amount of refrigerant. The inside of a A/C system stays very clean because there is no combustion deposits like an internal combustion motor. The contamination that does exist comes from moisture and/or oxygen in the system subsequent to an open system and/or insufficient evacuation prior to charging the system with freon, or metal contamination from lack of sufficient lubrication of the internal parts of the compressor. The automotive A/C systems are actually very robust, but somewhat undersized in the early Ferrari units. The coils and fans are to small at maximum (high temperature) cooling loads. This may be TMI. Sorry. Also, sorry about the TXV screen filter issue, I have seen screen filters at the evaporator of some A/C systems, but didn't know or remember regarding the Mondial TXV. Best regards, Jerry
Thanks Wade, I think it might be best to try the back flushing method to see if that part of the system is the issue, before dismantling the dash. Am I correct in thinking that you "back flush" from the low pressure line at the compression back through the Evaporator and the EV and then out through the hose coming from the drier? removed of course. will the EV allow compressed air and or flushing solvent through it or is the sprayer to small for that? Worth a shot. FYI Ferrari wants $369.74 for a new expansion valve, the 4 seasons valve which is the same costs $19.00 must be the Enzo tax. Thanks to all those who have responded with their experience, I'm sure I'll have it fixed by Winter!
4. When the system is shut off after running, the suction pressure should rise, and the discharge pressure should decrease until the two pressures are equal. The static equalized pressure will depend on the overall ambient temperature of the system. That ambient pressure can be determined from a temperature pressure chart for R12, or whatever refrigerant is in the system. A temperature pressure chart can be found on the internet. Thanks Jerry great info. Just so that I understand the chart provided, are you saying that the static pressures for both lines should equalize out to around 104 PSI at 94 degrees, with R-12? What would be an approximate amount of time it would take for these to equalize when the engine is turned off.
Yes, the temp press chart for R12 indicates approx. 104 psi at 94 degrees. The pressure is a direct constant relative to the temperature. Higher temp - higher pressure. That means in any enclosed container of R12, i.e. refrigerant tank, bottle, jug, or closed A/C system that contains a refrigerant that is in a "saturated" state, i.e. liquid and vapor in the same container, that will be true. The temp press charts for other refrigerants also apply to those respective refrigerants. The TXV is a mechanical device controlled only by the temperature/heat of/in the TXV control bulb. Temperature merely being an indictor of the heat/BTU's at the location where the bulb is attached to the suction line coming out of the evaporator. It is kind of neat that the TXV is "controlling" the amount of liquid refrigerant in the liquid line going into the evaporator, but is "controlled" by the amount of heated/hot vapor refrigerant coming out of the evaporator. It is called an evaporator because the liquid refrigerant is evaporated by absorbing heat from the air passing over the fins of the evaporator coil. Just the same as putting water in a pan on the stove, adding heat, the water boils and becomes a vapor (not the steam you can see). Taking heat out of the air to boil the refrigerant makes air coming out the A/C vents cooler. The condenser is called such, because the vaporized refrigerant is condensed from a vapor to a liquid by adding pressure from the compressor and removing heat into the air that passes over the fins of the condenser coil. That is also why the condenser fan must be moving a lot of air through the condenser coil fins. Air is not a great heat transfer medium. That is why the air coming off your condensing coil outside your house system is hotter that the outside air temperature. If you know the temperature rise and the volume of air moving through the condensing coil you can calculate the BTU'S being removed from you house. (Same for your car system) The reverse is also somewhat true. If you know the temperature reduction of the air going over you car evaporator and the volume of air going through the coil, you can calculate the BTUs being removed from the air inside your car. That is only true if no water vapor condensation occurs on the evaporator coil. That is another story. The liquid then passes through the TXV to start the evaporation cycle over again. I said all that to say this. The TXV will continue to allow refrigerant to pass through it when the system is shut off. As the suction line leaving the evaporator coil gets hotter when the system is shut off, the TXV continues to allow refrigerant to pass through it until there is an insufficient pressure differential to push any more refrigerant through the valve - therefor when the pressure equalizes the refrigerant flow stops, until the compressor is started again. Answer: This should take just a few minutes at most. There are some expansion valves that close when the system is shut off because of some internal springs and internal porting in the valve. Other valves have an internal or external bypass port to allow the pressures to equalize. Equalization of the pressures is good so the compressor can start against a lower "head" pressure. That is also why it is not a good idea to cycle the compressor on and off rapidly when the system is running. (True for your house system, too.) It will start, but it is hard on the belt and compressor clutch. The compressor would rather start against a pressure of 100 psi than 180 psi. There are some other technical parameters that can affect all of this, but this is the big picture. Sorry, I couldn't answer with just a yes or no. Bets regards, Jerry Webber
Thank you so much for your technical expertise, and your brilliant way of describing the workings of the A/C system in a way that even I could follow. Can't tell you how much I appreciate everyone's response to my situation. Enjoy your Labor Day Holiday! Mark in MS.
O.K. Just back flushed the low pressure line from the compressor line back to the drier line. I used a commercial a/c flush with solvent, at first I couldn't get anything to exit the drier line from the evap unit. I let the solvent sit about 10 minutes and then was able to get a decent air/solvent flow through the system. I filtered the used solvent to see what would come out, and it seemed to be full of sand like particles (drier medium I'm sure) seemed like the filter screen was plugged with this trash. ( there is a new drier installed) I was able to blow compressed air all the way through the low pressure side without any problems. backflushing seemed to clear out the EV screen. Anyway, thinking all was right with the world now, I vacuumed the system out for an hour, and it held good pressure. started the recharge process, it seemed to fill great, it took all three 14 oz. cans, and the pressures were where they should be, the condenser fan was running, the low pressure hose felt cold, the drier hose to the EV valve had a light coat of frost. 98 degrees here and humid. I put my thermometer in the center vents and had the fan on high, it was blowing very strong, BUT the temps. never got below 80 degrees on the thermometer in the vent. I checked to make sure the heater control was working, turned A/C off and temp control to full hot, heater is working fine, turned the temp. control to cold and the heater stopped so that end seems to be working fine. Compressor appears to be cycling properly. Must be getting close to a resolution here, not many parts left that haven't gone bad. Any suggestions why the air still blows warm? THanks
here is a pic of the debris that came out of the EV, hard to see, but it is allot like sand particles. also, a pic of the flush I used and how I contained the "Back-Flush" to the drier. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Just got off work and decided to see what the static pressures were and to give it another test run. static pressures were equal around 102PSI. started the car and the A/C, pressures dropped as soon as the compressor engaged, HOWEVER the low side went in to vacuum and I shut the A/C down. reading below it suggest the EV is stuck closed or the screen is still blocked. your thoughts. Also, the Static pressures are taking about 30 minutes to equalize: Below is from the internet site air-conditioning .com/tech/questions/82 How can I tell if the expansion valve is bad? This has to be our least favorite item to diagnose. We've had expansion valves quit working while on the road and show no signs of problem back in the shop. What's worse, an expansion valve can stick closed, stick open, or hang somehwere in between. Of all the bad expansion valves seen over the years, I think those that stick closed are most common. Those are the easy ones. Gauges will show very low suction side pressure along with lower than normal high side pressure. The low side may even draw into a vacuum. That's a big clue. Those that appear to be stuck closed may have inlet screens clogged with ground up desiccant particles. This will look like beach sand packed into the inlet.
