A/C trouble

[TommyBatchelor]

I found some posts about A/C error codes, but am still having trouble sorting mine out. Last summer I replaced accumulator, compressor, A/C hose, etc. Mechanic who put on hose told me I needed to replace low pressure sensor. I did that and went to fill up with r-134a. Used one of the cans with a gage on it. 

Before filling up I was getting B447c error. I kept clearing error and filling up bit by bit. The error kept accuring. After using pretty much entire 18 oz can the gage is reading like 90 psi (which seems bad as I thought low sidewas supposed to be around 34psi) and the error switched to b448c. No more b447 but I still get message saying compressor was shut off for its own protection because refrigerant is low. 

I think I saw something about the system needing 32 oz of r-134a? I don't want to overfill (if I haven't already).

Should I really put more r-134a in there, or am I missing something? Or both?

I appreciate the help!

[padgett]

Was the compressor running ? Have to disconnect the battery if has switched off. 90psi may be ok think more like 75 if static but low side should drop to 30-45 psi when running. "summer I replaced " did the system get flushed ? Was oil added ? Just switching from R-12 to R134A without flush and 134 oil is a recipe for disaster.. Think it takes more like 24-28oz (less 134 than 12).

[TommyBatchelor]

33 minutes ago, padgett said:

Was the compressor running ? Have to disconnect the battery if has switched off. 90psi may be ok think more like 75 if static but low side should drop to 30-45 psi when running. "summer I replaced " did the system get flushed ? Was oil added ? Just switching from R-12 to R134A without flush and 134 oil is a recipe for disaster.. Think it takes more like 24-28oz (less 134 than 12).

Not sure if compressor was running. I thought clearing the code on the crt would get it running again. So I need to disconnect battery?

Oil was definitely added (I got a kit that came with oil, new orifice, and o-rings). Can't remember if it was flushed. I'll have to call mechanic tomorrow and ask. I believe it had already been converted to r134 before by previous owner though. Had to replace parts because compressor froze up and there was a huge hole in the high line.

[Ronnie]

2 minutes ago, TommyBatchelor said:

Oil was definitely added (I got a kit that came with oil, new orifice, and o-rings). Can't remember if it was flushed. I'll have to call mechanic tomorrow and ask.

 

You might want to ask him if a vacuum was pulled on the system after replacing the parts. If a vacuum wasn't pulled you are just wasting Freon.

[Karlw144]

Also ask your mechanic if the replacement compressor came with an oil charge. Usually they do. If you added additional oil, and the compressor had oil, and there already was oil in the system, you also might have a problem with too much oil in the system. Hard to diagnose and correct. If there was no refrigerant in the system when you tried to charge it, 18 oz is definitely not enough. Let us know what you find out from your mechanic. 

[TommyBatchelor]

Ok, talked to both mechanics that worked on A/C. First guy installed new compressor and the silver cylinder with the low line quick connect. He said he put oil in compressor and put on plate to keep oil from leaking out without hose.

Second guy installed high line, definitely ran a vacuum pull, and possibly added refrigerant (he can't remember but says he probably did before telling me to replace low pressure sensor). 

System was not flushed (though first mechanic said everything looked fine) and we actually didn't end up replacing condenser or evaporator.

 

To clarify, do I need to disconnect the battery to allow the compressor to engage or does resetting the code on CRT do the same thing?

[TommyBatchelor]

19 hours ago, padgett said:

Just switching from R-12 to R134A without flush and 134 oil is a recipe for disaster.

System was already converted to 134A but compressor froze up. I actually had a smaller belt on it for a while to just skip past the compressor.

[padgett]

OK any time an AC system is opened, I pull a hard vacuum (won't affect oil) and just seal overnight to see if it holds. If so then I pull the battery negative cable and charge to about 40-50 psi static. Then reconnect, start engine, and AC on MAX with a fan in front of engine (to keep max pressure down), and fill to a nice set of pressures and cold outlet temp. My Reatta takes about a can and 3/4. High pressure should be in 200's. More is bad.

[Ronnie]

35 minutes ago, TommyBatchelor said:

To clarify, do I need to disconnect the battery to allow the compressor to engage or does resetting the code on CRT do the same thing?

 

Not always. This will help you keep the compressor running long enough to add Freon.
Compressor Kicks Out When Adding Freon - Solution

[padgett]

Ronnie: if system is evacuated or empty you can add near a can without running the compressor and get the pressure up to about 40-50 psi. Then when you start the engine/AC it will avoid tripping the "very low pressure" lockout.

[TommyBatchelor]

2 hours ago, Ronnie said:

 

Not always. This will help you keep the compressor running long enough to add Freon.
Compressor Kicks Out When Adding Freon - Solution

I'm using the paper clip trick. This got the clutch to finally engage off and on. The gage is going from 20psi to 50 psi as clutch engages and then disengages. When car is off it shows over 60 psi.

Should I keep filling until the clutch stops disengaging?

[Ronnie]

33 minutes ago, TommyBatchelor said:

Should I keep filling until the clutch stops disengaging?

 

Not necessarily. The Reatta has a sophisticated AC control system and a lot of variables can effect how it cycles on and off. You are in the ballpark and ready to fine tune it for the best performance.

AC System Fine Tuning

[TommyBatchelor]

Quick update:

First can was only 12 oz (second was 18oz) so I got one more 12oz can of r134a. When bypassing the low pressure sensor with a paper clip, I managed to get the compressor to stay engaged with the refrigerant can gage showing 40psi. 

When I reconnect the low pressure sensor I still get a notification saying pressure is too low. I did notice a bit of green fluid (I'm guessing refrigerant) dripping down the low pressure switch. I haven't seen it actively dripping but there are spots below that it dripped on. Could this be causing the pressure issue? 

Either way, is there any reason not to tighten the sensor more? 

Also can someone provide guidance on how to monitor BD28 without going into diagnostic mode on the crt (as I don't see how to go into diagnostic mode without turning off the A/C that I am trying to monitor)?

Thanks again!

[padgett]

Picture you showed should be static with the engine off. When compressor is running it should just drop and if gets under 20 psi it should cycle and pressure rise until the compressor kicks in again. If just sitting there I put a strong fan in front of the car facing the intake. As mentioned the ideal pressure varies with tempeature. but three cans (one 18 oz) sounds like too much. Sweet spot is when low side drops to about 30-35 psi and just stays there - does not cycle.

 

"I managed to get the compressor to stay engaged with the refrigerant can gage showing 40psi. 

When I reconnect the low pressure sensor I still get a notification saying pressure is too low."

 

That does not sound right. Bad low pressure sensor maybe ? What are BD27 (High side) and BD28 (Low Side) showing ? Will read in degrees C. When the AC is off, they should read close to ambient and the same.

Edited March 30, 2021 by padgett (see edit history)

[TommyBatchelor]

On 3/30/2021 at 7:35 PM, padgett said:

Picture you showed should be static with the engine off. When compressor is running it should just drop and if gets under 20 psi it should cycle and pressure rise until the compressor kicks in again. If just sitting there I put a strong fan in front of the car facing the intake. As mentioned the ideal pressure varies with tempeature. but three cans (one 18 oz) sounds like too much. Sweet spot is when low side drops to about 30-35 psi and just stays there - does not cycle.

 

"I managed to get the compressor to stay engaged with the refrigerant can gage showing 40psi. 

When I reconnect the low pressure sensor I still get a notification saying pressure is too low."

 

That does not sound right. Bad low pressure sensor maybe ? What are BD27 (High side) and BD28 (Low Side) showing ? Will read in degrees C. When the AC is off, they should read close to ambient and the same.

BD27 reads 39 C and BD28 reads 37 C

Does that sound normal? (Currently outside temp reading is 90 F with car sitting in sun all day).

Using my Reatta to go to work every day so haven't had much time to work on it further.

[padgett]

Yes, should read about the same with engine off. Is not a real temperature. Running 27 should go up and 28 down. Is not a real termperature. If 28 goes too low it will cycle.

[Ronnie]

2 hours ago, padgett said:

Is not a real temperature

Please elaborate. I thought it was a temperature that should match all the other sensors if the car has set over night so the temperatures normalize to ambient. Take a look here:  A/C Temp Sensor Troubleshooting

[2seater]

As far as I know it is a good way to see how far the temperature sensor has drifted from new. I do the same comparison?

[TommyBatchelor]

On 4/5/2021 at 9:49 PM, Ronnie said:

Take a look here:  A/C Temp Sensor Troubleshooting

I finally got a chance to check all of the temps mentioned at 3am after a night shift.

 

Ed23 30
Ed04 35

Bd32 42
Bd28 29
Bd27 33
Bd26 28
Bd25 26
Bd21 35
 

Does this mean I need to replace all my sensors? 😅

[TommyBatchelor]

I've also noticed that my average MPG has dropped from 17.5 to 16.5 after filling system with refrigerant. Is this to be expected even when compressor is disengaged?

[padgett]

a) no

b) those readings look like the AC is off

[2seater]

I don't think it has set long enough to equalize all the different areas of the car, and it must be a fairly warm area to be in the 70'sF at 3 am😎

 

I think any mileage change is purely coincidence.

[TommyBatchelor]

20 hours ago, 2seater said:

I don't think it has set long enough to equalize all the different areas of the car, and it must be a fairly warm area to be in the 70'sF at 3 am😎

 

I think any mileage change is purely coincidence.

Currently in Georgia 🔥. Been pretty hot (especially without ac). I'll try to get up early one day soon and check the temps again. Thanks!

[TommyBatchelor]

I checked the temps today at 11am. Is that early enough, or should I be trying for before 9am?

Ed23 22
Ed04 15

Bd32 68
Bd28 21
Bd27 25
Bd26 23
Bd25 49
Bd21 15

[2seater]

Well, I don’t know what change the timing might make, especially if not in a location with consistent temperature. The two interior air temperature, sun load and in car temp, are way in left field and would ignore them. A little sunshine through the glass would change things dramatically. It is interesting both the ecm and bcm report the exact same temperature, which makes sense if they are both reporting the single coolant temperature sensor. That leaves the underhood temperature in the air filter box MAT, the high and low side refrigerant and the ambient air temperature which are all within a four degree range. Not bad for over thirty year old sensors and would consider that a non issue. The coolant reading much cooler is sort of unusual, but I suspect as the day warms up, the coolant will lag behind the other temperatures under the hood? I would doubt these readings would have much effect on the AC performance but may want to check coolant temperature against a heat gun or actual thermometer.