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RSC'91
06-07-2013, 10:13 PM
On the black '90 SC I replaced the compressor, orfice tube, and suction line brand new when I replaced the head gaskets in January this year. AC has been ice cold until today. I left it idling this morning with AC on (92 degrees at 0800 here in Vegas) with in 2 minutes I heard a pop and a hiss followed by white smoke from under the hood. Suspected AC so I shut it off directly, popped the hood to find r134a and PAG oil all over air intake tube. The pressure relief valve on the back of compressor blew. I recharged the 134a and it blew cold the rest of the day. Pulled into a parking spot and it popped again. This sound like a bad orfice tube or something else? The red '91 did a similar release the day I bought it but never a repeat and has worked ever since. Any ideas will be appreciated its 110 degrees out there.

RalphP
06-07-2013, 11:55 PM
So what's the pressures at what ambient temperature of the condensor?

RwP

RSC'91
06-08-2013, 01:00 AM
27 low side, 52 evap temp, 227 high side, 104 ambient temp.

RalphP
06-08-2013, 03:04 AM
27 low side, 52 evap temp, 227 high side, 104 ambient temp.

Huh.

Based on the chart at http://idqusa.com/newsite/wp-content/uploads/2011/11/Temp-pressure-chart-33776F1-300x195.jpg , you shouldn't be having a too-high pressure problem.

So, what temp was the condensor? I see your "ambient", but that's open air - not really what I asked.

The heat off your car will increase the ambient at the condensor, it may be as high as 180F or so, if your car is overheating.

RwP

TbirdSCFan
06-08-2013, 12:17 PM
27 low side, 52 evap temp, 227 high side, 104 ambient temp. 227 = add more refrigerant. You should be pushing into the eeeek zone.. 300 But don't sweat it too much. As youre driving with air going across the condenser, that will come down. I run mine almost 3x ambient temp... so if its 90 out, Ill run 250-270. I get 40 out the vent on recirc (that all that really matters). Ill get 36 after 10 minutes on the freeway. However, you don't fill it with it on recirc. Windows open, max fan, norm a/c, and blend lever on max cold. OK to open the throttle a bit when fillling.

TbirdSCFan
06-08-2013, 12:32 PM
with in 2 minutes I heard a pop and a hiss followed by white smoke from under the hood. Suspected AC so I shut it off directly, popped the hood to find r134a and PAG oil all over air intake tube. The pressure relief valve on the back of compressor blew. Your radiator fan likely isn't running.. Thatll do it every time. When youre driving around, air moving across the condenser does the job of pulling heat, but sitting still, the fan does the work.

RSC'91
06-08-2013, 02:15 PM
Many thanks for the replies, I will double check the ambient temp at the condenser when I get home from work tonight and post. I replaced the fan and inline fuse at the solenoid just after I bought the car, I suspect this is what blew the original AC line before I bought the car. The fan does run as soon as the AC comes on and stays on until it is turned off, i'm pretty sure it was running when the valve blew because the smoke was coming out from under the car and rear of the hood. It was running when I recharged the freon shortly thereafter.

RSC'91
06-08-2013, 11:51 PM
I changed out the orfice tube with a new one through warranty. The current readings are 39 low side, 147 high side (it will not increase any high nor does it fluctuate with rpm) 51 evaporator, 98 degrees two inches from front of condenser, and 140 at condenser. It popped again about 8 minutes into running at 1200 rpm.

KMT
06-09-2013, 12:08 AM
Guessing you have a restriction you haven't located and/or your gauges aren't telling the truth.

What happens if you only fill it 1/2 way according to them?

How many times have you vacuumed it down? How long does that take? What happens if you use a freestanding fan to blow air across the condenser? How old are the hoses? Do you have another gauge set?

RalphP
06-09-2013, 12:22 AM
Leave the gauges on the car and repeat what blew it earlier.

At what pressure is it popping off at?

If under 400psi, then there's a really good chance you have a defective high pressure relief valve.

Be like a circuit breaker rated at 40A that keeps tripping at 22 ... you can hunt and hunt a short all day long, but never find it, until you're monitoring the current draw and see what level it pops at.

RwP

TbirdSCFan
06-09-2013, 02:35 AM
Guessing you have a restriction you haven't located and/or your gauges aren't telling the truth. Agree. . or the compressor has bit the dust. 140-something is either not enough refrigerant or bad compressor.

RSC'91
06-09-2013, 02:00 PM
Sure appreciate the input guys, I borrowed a set of gauges just to be sure. Mine are brand new but you know how far quality goes these days. Same readings. The pump and both hoses are brand new as of the first of the year, I am certainly not an AC pro hence the questions but it seems like a high pressure relief must be the culprit and possibly the pump. If the high side will not push past 150 and 275 should be the norm, I have to wonder if the pump is failing. I let the darn thing run for 35 minutes last night hooked up to the gauges hoping to see where it popped and short of the low readings it worked fine. Admittedly I did not add 134 to the maximum. The trip to work was nice and cool today but it was only 97 out this morning. What would you guys suggest as the next step? Replace the line with the valve, the pump, or both? Thanks again.

Shawn

RSC'91
06-09-2013, 02:07 PM
Guessing you have a restriction you haven't located and/or your gauges aren't telling the truth.

What happens if you only fill it 1/2 way according to them?

How many times have you vacuumed it down? How long does that take? What happens if you use a freestanding fan to blow air across the condenser? How old are the hoses? Do you have another gauge set?

Vacuumed down three times since hoses replaced near the first of the year. It took about 25 minutes yesterday. I have not placed a fan in front of the condenser. I did try a different gauge set, almost exact readings. While troubleshooting I did try filling half way and the system did run but the compressor kept kicking out when the low side reached approx 15 psi then would cycle.

RSC'91
06-10-2013, 02:51 PM
Although it has blown cold air the last two days, running it with a low charge is simply not the correct repair. I just ordered a new compressor, suction/discharge line, condenser, accumulator and just replaced the orfice tube on Saturday. Short of the evaporator it will be all new, is it a bad idea to use the old evaporator? Would you guys suggest replacing it as well? Not that I am opposed to the work albiet the hardest part. The car has 201,765 miles on it but is from Salem Oregon where the system might have been used off and on two months of the year. Down here its an absolute must an easy 7 months. Thanks again for sharing your information.

TbirdSCFan
06-10-2013, 03:48 PM
Although it has blown cold air the last two days, running it with a low charge is simply not the correct repair. If you can get a new pressure relief valve, that might just be the problem. You were seeing no more than 140s high pressure.. it shouldn't have tripped. Seems like we didn't really nail the cause. But OTOH... replacing everything under the hood is, believe it or not, fairly standard practice in the AC repair business. It has more to do with mechanic time spent under the hood though.


I just ordered a new compressor, suction/discharge line, condenser, accumulator and just replaced the orfice tube on Saturday. Short of the evaporator it will be all new, is it a bad idea to use the old evaporator? Would you guys suggest replacing it as well? Not that I am opposed to the work albiet the hardest part. The car has 201,765 miles on it but is from Salem Oregon where the system might have been used off and on two months of the year. Down here its an absolute must an easy 7 months. Thanks again for sharing your information. The evaporator is such a big job, that I wouldn't recommend it unless you're rather certain its leaking. Flushing it is usually sufficient.. and some people will say that even that is a waste of time but in your case, I'd definitely at least blow line air through it to be sure you don't have any restrictions. If everything held a vacuum before, its chances are good.. not perfect, but good enough to use it.

Also, I mentioned this in another thread somewhere, but if your accumulator is new from a previous job.. I wouldn't replace it just because it got 2 sips of open air when you disconnected the lines.. :rolleyes:

Im in Dallas, so yeah i appreciate what it means to have fully working AC. If you were using the original dumpy r12 condenser, you'll have much better results with the newer replacement. :)

TbirdSCFan
06-10-2013, 03:59 PM
While troubleshooting I did try filling half way and the system did run but the compressor kept kicking out when the low side reached approx 15 psi then would cycle. BTW.. when its low thats normal. You have to have sufficient charge to get it to not cycle quickly.

KMT
06-10-2013, 04:04 PM
BTW.. when its low thats normal. You have to have sufficient charge to get it to not cycle quickly.

The question is....did that example also pop the valve...

RSC'91
06-10-2013, 04:13 PM
[QUOTE=TbirdSCFan;1037563]If you can get a new pressure relief valve, that might just be the problem. You were seeing no more than 140s high pressure.. it shouldn't have tripped. Seems like we didn't really nail the cause. But OTOH... replacing everything under the hood is, believe it or not, fairly standard practice in the AC repair business. It has more to do with mechanic time spent under the hood though.

Would you use Dura 2 or R141b to flush the evaporator? I really believe your correct about the pressure relief valve and I did try to obtain just that part but it only comes complete with the suction/discharge line. Since I have not been able to sufficiently charge it I really cannot say for sure the compressor is bad, but I really need this to work 100% by Thursday for a trip to Southern California and its a scorcher crossing the desert in a black car with no AC. Its also getting expensive breaking the system open for each component. Figure I will just hang on to the pump for a future need, I do own two of these cars. I'd take the red one but it needs a lower passenger side control arm. Always something...

RSC'91
06-10-2013, 04:19 PM
The question is....did that example also pop the valve...

That's what I do not understand about it, the low side was reading 39lbs if memory serves, the high side was near to 145, and it had been running less than 5 minutes when it popped. I added additional refrigerant to a low side reading of 30lbs, high side just over 140 and it has been cold to 45 degrees while on the road in recirc mode. Problem there is it cycles for low refrigerant (pulls down to 13-15lbs) and that will likely finish off a clutch pretty quickly if not additional damage somewhere else.

RSC'91
06-22-2013, 03:10 PM
So the trip to California was trouble free, new AC blew cold (almost uncomortable, gauge read 39 at the vent) the entire trip. I do wish I knew the true root cause but am pleased it is now working as it should. I ended up replacing the accumulator, pump, both suction/discharge line, and the orfice tube/line. Thank you all who helped diagnose and suggested a course of action.

PDQ SC
06-22-2013, 03:17 PM
You didn't replace the compressor?

RSC'91
06-22-2013, 03:32 PM
You didn't replace the compressor?

Oops, yes I did replace the compressor. Sorry, I should have written compressor as opposed to pump. The accumulator, both lines, and compressor were replaced.

PDQ SC
06-22-2013, 04:10 PM
That compressor was likely the problem. You have an expensive A.C. Hope it keeps you cool. I bought one of my '90's from a member in Vegas (in June). I know it gets hot as hell in the summer.

TbirdSCFan
06-22-2013, 05:05 PM
Problem there is it cycles for low refrigerant (pulls down to 13-15lbs) and that will likely finish off a clutch pretty quickly if not additional damage somewhere else. Ford AC is a CCOT design. Cycling Clutch + Orifice Tube. Its designed to cycle on/off so you're not going to damage it. On a hot summer day with high humidity, it may be on 100% of the time. Turn it on and enjoy the cold air ;)

TbirdSCFan
06-22-2013, 05:09 PM
AC blew cold (almost uncomortable, gauge read 39 at the vent) the entire trip. And thats all that really matters. :cool: