1991 PA Ultra A/C goes into Econ mode

[JoeNezz]

I have a strange problem, When I bought the car a year ago, the previous owner told me he had a used compressor installed but after charging the system they could not get the compressor to stay running.
when I got the car the A/C clutch relay was missing.

After replacing the relay I found the system would run fine for 15 to 20 minutes then the compressor would cut out & after about 30 seconds the A/C goes into Econ mode & I have to disconect the battery to re set it.
Refrigerant seems ok lots of cool & the compressor runs continious on a hot day.
I have tried jumping out the low pressure cycling switch & the high pressure switch to see if I had a bad pressure switch & after resetting the codes it still went into Econ mode.

It seems only to do this after the car has been driven for a while or had time to warm up.
Even if you dont use the A/C & let the car warm up first then switch the A/C on the compressor will not start & if you leave it set on Auto for about 30 seconds the computer switches it to Econ

If the Car sits all day or over night, the next time you use it the compressor will stay on again for 15 or 20 minutes untill the car has warmed up.

Does anyone have any ideas what could cause this?

Thanks in advance,
Roger

[HotZ28]

Do you have auto climate control? If so, check the codes. Write them down, then clear the codes and see if they come back. It sounds like a code 10, 13 or 15. It could also need a shot of freon (code 66).

Auto Climate Control Diagnostics
This procedure will work on 1992 and 1994 models with ATC, and may also work on 1988-1991 models.

The diagnostic mode also contains a data list mode and an override mode.

Be careful not to select modes 01 or 02, as these are different modes, and may cause problems.

If you suspect you are in the wrong mode, press OFF repeatedly until you exit to normal mode. If the temperature display flashes for 2 minutes when the ignition is turned to RUN, a trouble code is set.

1. Turn ignition to RUN. Press OFF and WARM (temperature up) buttons simultaneously.

2. Watch the segment test, then the trouble codes will be displayed.

3. Code Key:

00 - No codes

10 or 110 - Ambient Temp Sensor circuit open or shorted.

13 or 113 - In-Vehicle Temp Sensor circuit open or shorted.

15 or 115 - LH Solar Sensor circuit open or shorted.

35 or 135 - Data Line failure - HVAC Control Assembly

38 or 138 - Data Line failure - PCM

40 or 140 - Driver Air Mix Motor circuit open or shorted, or not calibrated

48 or 148 - Long Term Freon Loss

52 or 152 - Keep Alive Memory lost; sets with battery disconnected

66 or 166 - Low Freon

A number 1 prefix indicates a history trouble code

4. Press OFF twice once codes are displayed to end diagnostic mode, OR to clear trouble codes, press FAN DOWN three times (make sure 03 is displayed).

Once 03 is displayed, press FAN UP to clear trouble codes. Then repeatedly press OFF to end diagnostic mode.

[JoeNezz]

no codes registered except 152, probably from me dropping the battery to reset.
But I will do the sensor tests just to be sure.

When I did the HVAC programmer test I found pins "C" 5 & 7 of the programmer connector both read 9.6v to ground while pin 13 reads 12.57v & pin 12 reads 11.98v with respect to chassis ground on door hinge.
the manual just says these should pins should be battery voltage.
Is the slight difference in voltage normal or does it indicate I have a wiring problem?

Does anyone know whare I can get an electronic schematic for the HVAC programmer board, programmer #16149874 ?
Thanks, Roger

[Gocart879]

hello i have a lesabre limited with an AC problem, when i turn my AC on, (stndrd controls not digital) the compressor will click on and only run 3-5 seconds and click on and off every 3-5 seconds continuosly. the blower works correctly and it blows out as cold as you can imagine. But speaking of those relays you were talking about what do they do? can i use any other relays to check them. can anyone point me in a direction.

[HotZ28]

All the relays are the same on the firewall. You can change one to another. If your compressor is cycling, it sounds like the low pressure switch located on the receiver-dryer near the firewall. If it senses low pressure (low Freon level usually), it will disengage the clutch. You can jump out the female connector long enough to see if that is the problem. I have seen many of these units cycle and cool reasonably well, however, just a 1/2 lb. of Freon will take care of the problem.

[Gocart879]

funny thing is i believe it was just recharged last year sometime, i will take a look at it. but how do you jump out the female connector and where is it located.

[HotZ28]

Anytime the compressor is changed, you could generate a small leak. I have some leak freon out within a few weeks, and some over the winter months.

The connector is attached to the pressure switch located on the side of the receiver near the firewall. Follow your hoses along the fender well, passenger side of car, and you will see them terminate in the evaporator box. The one you want is going into an aluminum tank (accumulator, receiver-drier), On the side of that tank, you will see an electrical plug with two wires connected to the switch. Squeeze the connector and pull it off the pressure switch. Strip a small piece of wire on both ends and connect it between the two terminals inside the female plug and just let it sit there until you conduct your test run. Remove, the wire later after your test, and reconnect to switch

[Gocart879]

well, it appears my problem is low freon. thankyou for your quick response, i did the test and the compressor stayed on for about 2 minutes thats as long as i had the car on. so my next question is where do i get it recharged besides the dealer. i see the kits in stores but they are for 134 not r-12. what can i do?

[HotZ28]

Well, now comes the hard part, where can I find a reputable shop that has R12? The EPA banned the new production or R12 in 1995, so finding some, is getting more and more difficult. It is quite ironic that the banning of production coincided with DuPont’s expiration of paten rights (Government lobbyist I guess)! Most of what you find in the market today is recycled. Virgin R12 is still out there, but most shops will not buy it. The average shop would prefer to convert your system over to R134 and reap the benefits from the extra labor to do so. However, if you have a small leak in the system, it might be cheaper in the long run to pay for the conversion, considering the current price difference between R12 & 134. Most shops that do the conversion will charge about $150.00, just for the conversion and addition of oil & R134). Some shops will tell you all you need to do is suck down the system; change to ester oil, install conversion fittings and pump the system back up. Stay away from those guys!! At the very minimum, you need to install a new accumulator-drier and orifice screen (about $60.00) and flush the system. It is also recommended to replace all the O-rings in the system with Viton O-rings, which has a higher resistance to deterioration with the use of ester oil. If you’re planning to keep the car for a few years, it might be worth the additional expense to replace the O-rings.

So what should you do? Call several AC shops in your area and ask how much they charge per pound for R12, installed. (If your system is cooling fairly well you may not need more than a ½ pound). Also, ask how much they charge for the R134 conversion using the method described above. All of the AC service centers are now required to use reclaim equipment. They will suck your system down to see how much Freon you have, then pull a vacuum and add back to the system capacity. (If you do the R134 conversion, it only takes 80% of the R12 recommended capacity). If you have the right equipment and you are EPA MVAC 609 certified, you could do it yourself. You can still find plenty of R12 on EBay. Just do a search for Freon. Most quick lube places can add R12 for you, however beware, it could be contaminated with other chemicals and Freon types that they suck from other vehicles. You never know what people will put in their system prior to going to a quick lube! It may look like an R12 system, so the guys, (mostly teanagers) just suck it into their R12 tank contaminating the whole tank. :22yikes:

Beware, there a lot of shady AC technicians out there, so find someone you can trust & depend on, that say what they will do & do what they say, and not take you to the cleaners in the process!! Good luck.

[JoeNezz]

True the camel jocky that worked on my A/C befor I owned the car was pretty bad, I hear from the previous owner that they did not even know how to use the equipment & they charged the system with Duracool HC12a
i dont know if that is causing my problems or not, I hear computer controlled systems dont like HC12 because of the lower operating pressure, they adjusted the cycling switch lower to avoid short cycling but now it does not cycle at all so if the computer counts no cycles to be just as bad as too many cycles in a given time,then I am in trouble, I guess I need to find what ecm holds the cycling paramiters & adjust the limits, even if it means writing a new prom. does anyone know anything or have any ideas as I am probably way ahead of my self as from what Ive read if I jump out the low pressure cycling switch the unit should run continious if the switch is bad or if low freon is the problem.
so that tells me that the ECM or HVAC does not count a continiously closed circuit as a problem just too many cycles in a given time to indicate low freon, is this correct ?
in my case somthing else is telling the HVAC programmer not to engage the compressor once the engine is warm, then after 30 seconds the ECM switches it to econ mode, I tell U I am about ready to buy one of those portable A/C units & a big power inverter, strap it into the back seat & hang the core out the window.

[Gocart879]

well, it appears that after letting my vehicle run for 5-6 minutes the compressor cycles get longer and eventully turn into the normal cycles. what happens if it does have low freon and i let it run like this? also is there another method for determining if the switch is bad, i cant imagine it blowing cold air and being low on freon especially after it was charged by my brothers A/C unit repair shop. He deals with all types of refrigerants so i know i dont have a problem. let me know?

[HotZ28]

Quote:

"I jump out the low pressure cycling switch the unit should run continious if the switch is bad or if low freon is the problem.
so that tells me that the ECM or HVAC does not count a continiously closed circuit as a problem just too many cycles in a given time to indicate low freon, is this correct ?"

You are correct in your assumption above, with the exception of "low Freon is the problem".
Duracool 12a Has been labeled (UNA), unacceptable; illegal for use as a CFC-12 substitute in motor vehicle air conditioners. The "camel jocky" that installed Duracool 12a in your system violated Federal law!!


The following cut was taken from the EPA MVAC 609 certification manual:

ASU = acceptable, subject to fittings, labeling, no drop-in, and compressor shutoff switch use conditions.

UNA = unacceptable; illegal for use as a CFC-12 substitute in motor vehicle air conditioners.

HC-12a® UNA 6/13/95 OZ Technology Flammable blend of hydrocarbons; insufficient data to demonstrate safety

Duracool 12a UNA 6/13/95 Duracool Limited This blend is identical to HC-12a® in composition but is manufactured by a different company

R-405A UNA 6/13/95 Greencool Contains a perfluorocarbon, which has extremely high global warming potential and lifetime.

1) R-401A (made by DuPont), R-401B (DuPont), R-409A (Elf Atochem), Care 30 (CalorGas), Adak-29/Adak-12 (TACIP Int'l), MT-31 (Millenia Tech), and ES-12R (Intervest) have not been submitted for review in motor vehicle air conditioning, and it is therefore illegal to use these refrigerants in such systems.

(3) Although some blends contain hydrocarbons, all blends that are ASU are nonflammable as blended.

(4) Freezone contains 2% of a lubricant.

(5) HCFC-22 content results in an additional use condition: must be used with barrier hoses.
UNA ASU

[HotZ28]

There are many types of Freon’s, like Freon-11, Freon-12, Freon-22, Freon-113, Freon-502 (also called Genetron-12 if from Allied, etc), or generically called R-12, R-22, etc.All these refrigerants have different boiling points and serve different purposes. R-11 boils at around 75 deg F, and once made an effective flush for cleaning and servicing A/C systems to clean out debris from failed compressors, etc. R-11 and R-12 are also known as CFC-11 and CFC-12. CFC means chlorinated fluorocarbon. As you know, CFCs are thought by some to harm the ozone layer in the upper atmosphere. Whether CFCs hurt the ozone or not is immaterial now, as laws are in place to ban them in the US (no new production of them, you can still use what you hoarded). For the automotive industry, Freon means R-12.

Three common methods exist for throttling back the A/C when (or if) the car gets cold enough. The simplest method is to have a thermometer at the evaporator (air) outlet and shut off the compressor when it drops to approximately 32F. The last two are much more common and both look at the suction (low side) pressure to decide when to stop/slow down cooling. As the evaporator cools down, the suction pressure also drops. Older cars (such as using the infamous GM (R4) compressor, have a switch in the low pressure side of the system which opens at about 24 PSIG, cutting off the compressor. The evaporator warms up, and when the pressure reaches around 40 PSIG, the switch closes again, restarting the compressor. This method causes a lot of wear and tear on the compressor clutch. Newer cars, have variable displacement compressors, which run continuously instead of cycling off and on. They have a swash plate instead of a crank shaft to anchor the pistons. The stroke of the pistons in this type of compressor may be varied from maximum to almost zero, by varying the angle of the
swash plate. A GM (V5) is a common example of this type of compressor. These compressors usually have an internal mechanical arrangement to control the swash plate based on the suction (low side) pressure. They are usually set for about 28 PSIG. When the car is hot, the suction pressure will be much higher than 28 PSIG, so the compressor operates at full stroke The car cools down the suction pressure drops down through 28 PSIG, and the swash plate moves, reducing the stroke of the pistons, and lowering the capacity of the A/C, and the suction pressure will stop dropping, and stay at around 28 PSIG. The compressor will continue to reduce displacement by maintaining the suction line at 28 PSIG if the car cools down too much. If the sun comes out, and the car begins to heat up, the suction pressure will rise above 28 PSIG, and the compressor will increase it’s displacement to bring the pressure back
down to 28 PSIG.

Frigc FR-12 and Freezone / Freeze 12 offer inferior cooling capacity with the last two (most common) types. There is a horizontal red (really magenta) line crossing the vertical (pressure) axis at 28 PSIG, the common setpoint for variable displacement compressors. The 28 PSIG line intersects R12 at about 29F temperature, so that is where R12 will boil. Once the A/C system has stabilized at 28 PSIG suction pressure, and the evaporator air should be about 39F or 10 degrees warmer allowing for thermal drop across the evaporator. This will vary somewhat depending on the blower fan speed. The 28 PSIG line intersects the (average) of the Frigc & Freezone/Freeze 12 curves at about 40F. Adding the 10F evaporator drop, means that the duct temperatures will never get below about 50F for FRIGC/Freezone/Freeze12, or about 10F warmer than with R12.
For a variable displacement compressor to offer good performance with FRIGC / Freezone / Freeze12, it would have to have it's setpoint changed to 19 or 20 PSIG from 28 PSIG. This is very difficult to do at the present time. This pressure is fixed and there is no easy
adjustment. Even if the setpoint could be lowered to 19 PSIG to make FRIGC/Freezone/Freeze 12 work better, there is roughly a 25% reduction in pressure and corresponding reduction in massflow and lowered capacity. The suction pressure is lower, therefore less gas molecules enter the compressor (about 25% lower) and circulate in the system so it cools less.

[JoeNezz]

ok I reset the PCM & cleared any error codes in the A/C diagnostics, then drove the car from cold into town & back, it was ok on the way to town but once I restarted the car the compressor did not start & the system went into econ mode 30 seconds later.
After I got home I checked the A/C diagnostics & no codes were loged, I then checked the PCM diagnostics & found a code 66 excessive A/C cycling registered.
I know this is not true the compressor runs continious in this humid weather & its very cold.
I then disconected both the high pressure cutout & the cycling switch & ran a jumper wire from the "A" wire on the high pressure sw socket, to the "B" wire on the cycling sw thus feeding a direct signal from the HVAC programmer to the powertrain control module bypassing all the A/C pressure sensors other than the Fan pressure switch.that it shows in the electrical service manual.
I then reset the PCM & Cleared any A/C diagnostic codes.
I waited untill the car was cold again & tried it, again it ran ok for a while then put it into econ mode again, I checked & again no A/C codes logged in the A/C diagnostics but a 66 code in the PCM. excessive cycling, I then reset & cleared all codes & jumped out the compressor relay & tried it again while it was hot, after a minute or two it switched to econ mode but this time the compressor continued to run, I shut it down & checked, again 00 on the A/C diagnostic & 66 on the PCM.
I unhooked all the jumpers, reconected the switches & relay & went & had a cold Beer.

Now all this seems to tell me that the HVAC programmer os working ok as no errors are being logged to the to the A/C diagnostics, cycling & high pressure switches are ok, along with ambiant temp & climate control sensors or an error would be logged,that pretty much leaves the question why is the PCM setting a 66 code when the system in not cycling ? & why only when its hot ? faulty pcm? or bad data line?
Time for another cold one & I think I will ponder the universe for a few hours, thanks for all the input so far,
if anyone has any ideas about this, just jump in.

Roger

[Gocart879]

anyone have any ideas for my last post? let me know