Code ACM 1347 and 1348 - But Gas is Present

[coolnesss]

I have a 2002 ETC. 86k miles.

I was getting ACM 1347 and the A/C turned itself off. I took it to the mechanic, and he recharged it and it worked for a few days, and then the code came back and turned off.

The mechanic tested it, and the system is full and has the right pressures.

Then after driving it a few days, I got ACM 1348, and it turned off.

With the 1347 I was able to clear the code and the system worked perfectly for awhile.

Mechanic says I need a sensor - does this make sense? And, if so, which sensor? He's not sure which sensor it needs.

I don't expect it matters, but in case it does: I have multiple electric system codes - MSM B2115 history, MSM B2118 and B2119 history, MSM B1656 history, SDM 1327 history, RFA U1064 history, and recently, after the A/C thing started TCS 1286 and 1287 history, and just for fun PCM 0420. The 0420 goes away for awhile when I clear the code, finally comes back.

THANKS.

[Cadillac Jim]

You need the low pressure Freon sensor. I would take it to someone who knows what a Freon sensor is.

I'll come back and look at your code list in a few minutes. Or, you can download my list from a link in my signature block. I also have a FSM for 2002 and can look at the procedure for when you have code B1348 but the Freon pressures are OK.

[barczy01]

371586422926 ebay. A great kit I have installed a couple of them. I would also ACDELCO 152876, low pressure switch and replace the oring too. The ac compressors start to leak overtime at the body casting.

[Cadillac Jim]

ACM
B1347 Very Low A/C Refrigerant Warning
B1348 Very Low A/C Refrigerant Pressure

MSM
B2115 Recline Sensor Failed
B2118 Front Vertical Sensor Failed
B2119 Lumbar Forward/Aft Sensor Failed
B1656 EEPROM Write Error

SDM
B1327 Vehicle system voltage below 9.0 volts

RFA
U1064 Loss of Communications with DIM

TCS
C1286 Steering Sensor Bias Malfunction
C1287 Steering Sensor Rate Malfunction

PCM
P0420 Catalyst System Low Efficiency

The B1327 means that the battery voltage drops below 9 Volts when you start the car, or, worse, while it is idling with the lights on. It's possible that you just need to leave it on a trickle charger overnight, but more likely you need to clean the battery cables too, and you should have your battery checked. This does NOT mean there is anything wrong with the air bags.

I would ignore the rest of the codes until you have a certain fix on the battery.

The A/C Cycling Switch is in the A/C line that runs across the firewall above the master cylinder. It's the last item in the A/C line on the passenger side before it bends down to go into the firewall. It's easy to reach and the FSM says to simply remove and replace it. I don't see anything about Freon recovery and refill. Looks like a quick no-brainer.

There are lots of other things mentioned in getting to replacing the switch, like IGN 1 fuse and such.

You can see why you could reset the B1347 and go, but not the B1348.

[KHE]

The "mechanic says it needs a sensor but not sure which one"... He'll throw parts at it while charging you and still not fix the problem.

If the system says it is low on refrigerant, it is low on refrigerant. If the mechanic did not recover the refrigerant and weigh the amount that was recovered, he has no idea if the system is "full". The pressures are a guideline for troubleshooting the system, not to see if it has the correct amount of refrigerant.

I recommend taking the car to a competent A/C shop and have them use an electronic leak detector or UV dye to pinpoint the source of the leak.

[coolnesss]

Gentlemen, THANKS for all of this.

It can't hurt to replace the freon sensor, so I'll do that.

Kevin, the mechanic isn't charging me like that - he's honest but not the most knowledgable mechanic in the world, but I can depend on what he says, and when he says he doesn't know - which is what brought me here about this. The gas has been leak tested. It's not leaking - it's full. He did evacuate it and weigh what was in there.

Can I test the voltage output of the battery by attaching multi-meter leads to the respective battery posts during cranking? The cranking has seemed to me to be slow for quite a while, but I took it to a regulation competent shop; they tested it with a fancy tester and said the battery and charging system is good. The cranking hasn't changed since then. I'll clean the cable ends and see what happens.

Hmmmm.

[KHE]

If the recovered refrigerant was 2.0 lbs. then I would agree the system is at capacity. It is possible that the sensor is bad but it could be a bad connection at the sensor terminal. Not to say the sensors never fail but their failure rate is extremely low. The low side temp sensor is on the A/C line between the orifice tube and the evaporator.

[Cadillac Jim]

It just occurred to me that there might be air or moisture in the A/C system, or the drier/accumulator might be blocked, or the expansion valve might be clogged.

[BodybyFisher]

Very easy to test and replace. To test jump the terminals of the low pressure sensor connector with it detached. Clear codes, run AC, does it get cold?, yes? Replace LP switch.

It unscrews its an easy job, you dont need to depressurize the system there is a schrader type of valve in there that closes when the switch is removed.

The caution is, if the system IS in fact low refrigerant you run it, if it dies NOT get cold with the switch jump stop AC immediately and discontinue jump.

I have one leaking refrigerant and oil right now on a 98 Eldo and will replace it this week.

[BodybyFisher]

Clean connections, have battery load tested and check the battery for proper cranking amps mine is 990 cold cranking amps. A voltage test alone wont tell the whole story.

Your starter may need a rebuild, brushes and bearings may be worn. Causing a high current draw also.

Bad grounds or

Your battery cables could add resistance to the circuit look for cracks in the insulation, moisture gets in there, corrosion starts, increasing resistance and current draw. Could also be a solenoid switch bridging a bad high resistance connection.

The starter owes you nothing after 14 years, to change it you need to remove the intake, if the intake seals are ok you can reuse them but I wouldnt. You will need quick disconnect tools for the fuel lines. At that point I would measure the starter 12v start power wire for resistance.

Use inch pound torque wrench to retorque intake my memory tells me 89 in lbs.

[KHE]

Very easy to test and replace. To test jump the terminals of the low pressure sensor connector with it detached. Clear codes, run AC, does it get cold?, yes? Replace LP switch.

It unscrews its an easy job, you dont need to depressurize the system there is a schrader type of valve in there that closes when the switch is removed.

The caution is, if the system IS in fact low refrigerant you run it, if it dies NOT get cold with the switch jump stop AC immediately and discontinue jump.

I have one leaking refrigerant and oil right now on a 98 Eldo and will replace it this week.

I believe the low pressure temp sensor does not have a schrader valve - the refrigerant needs to be recovered before replacing this sensor. The thermistors can't really be jumped - the ACM looks for a difference in readings between the two sensors to determine the charge. What you're referring to is the low pressure switch - between the evaporator and the accumulator. His codes point to the low side temp. sensor.

[BodybyFisher]

Kevin, we are not speaking of TEMP we are speaking of PRESSURE here no, low pressure. You are speaking of a temp switch.

He is getting these 2 codes

B1347 Very Low A/C Refrigerant Warning
B1348 Very Low A/C Refrigerant Pressure

You taught me all I know about AC so I defer to you, but aren't we speaking about #13 in this photo, and if that is the case I jumped it and also removed it without depressurization.

[Logan]

Yikes.....conflicting service manual info....for 2002 Eldorado.

My GM info shows that as the low temp sensor...#9 in mine.

[BodybyFisher]

WOW, was there a change? The codes the original poster posted were for pressure.

[Logan]

Looked again....2002 Eldo. Something moved.

Low pressure switch uses Pink and Dark Green wires.

New pic from service info shows both sensors.

#1 is low pressure switch

#3 is low temp switch

[BodybyFisher]

Very odd, did 2002 Eldo have coil packs, are those 4 coil packs. Odd that they would change the position of the low pressure switch

[Logan]

No....the 2002 Eldo had the 2000 engine update with the in-head coils.

Could be a misprint....wouldn't be the first time.

Maybe they moved it to facilitate servicing the coil pack cartridge.

[KHE]

When the system displays the low refrigerant message, connect a A/C pressure gage to the low side fitting. If the pressure is above 10 psi, check for battery voltage on the dark green wire (opposite the fuse side of the pressure switch) on the pressure switch. If battery voltage is not present, the pressure switch is bad. If there is battery voltage on the dark green wire, then the problem lies in the low side temperature circuit - connector, sensor, wiring, etc.

Someone with a 2002 manual should be able to post the wiring diagram if the color I referenced is not correct.

The static pressure (pressure without the engine running) should be around 90 psi, if it is very low, there is a low refrigerant charge.

[Logan]

Uses pink and dark green wires. Post #15.

My GM service info shows the same image and location for the low pressure switch location back thru 1998 Eldorado.

[airmike]

Could someone explain "low temp switch" please? I understand low pressure, but didn't know about low temp in an air conditioner system

[Logan]

From the GM ESI service manual:

"A/C Temperature Sensors
The HVAC control processor monitors the refrigerant temperature and sends the data to the PCM on the class 2 serial data circuit. The PCM monitors the A/C high temperature sensor signal along with the coolant temperature sensor in order to determine the need for the cooling fans and prevents the A/C compressor from operating at high discharge pressures. A 5 volt reference signal is sent from the HVAC control processor to the A/C refrigerant high temperature sensor over the A/C refrigerant high temperature sensor signal circuit. A thermister inside the sensor varies the voltage. That varied voltage provides a signal to the software inside the HVAC control processor. Remaining voltage from the A/C refrigerant high temperature sensor is sent back to the HVAC control processor ground through the low reference circuit.

The HVAC control processor monitors the A/C low temperature sensor to determine the low side pressure based on the pressure/temperature relationship of the R-134a. A 5 volt reference signal is sent from the HVAC control processor to the A/C refrigerant low temperature sensor over the A/C refrigerant low temperature sensor signal circuit. A thermister inside the sensor varies the voltage. That varied voltage provides a signal to the software inside the HVAC control processor. Remaining voltage from the A/C refrigerant low temperature sensor is sent back to the HVAC control processor ground through the low reference circuit."

[BodybyFisher]

I know, I am confused also airmike. I need to buy a few manuals I can see. The low pressure switch that triggers the AC low pressure code and message has been in the same location on my 95, 96, 97 and 98. I am about to change one on a 98, got the acdelco switch from rockauto yesterday, it is leaking oil and I have to assume its leaking refrigerant, as the vehicle has a low pressure message on the dash.

Thanks Kevin, that is a better way to test the low pressure switch, my inclination is to immediately jump it, but I recall you not liking that option as you jump a compressor that has low refrigerant if the switch is in fact good. But let me ask, is it low pressure that damages the compressor or low oil?, or both?

[KHE]

But let me ask, is it low pressure that damages the compressor or low oil?, or both?

The oil is miscible in the refrigerant and the refrigerant circulates the oil in the system. Low pressure is a resultant of low a low refrigerant condition. The result is less oil will be circulated to the compressor resulting in damage to the compressor.

[BodybyFisher]

Thanks for that clarification

[Cadillac Jim]

It's obvious from what I got from the procedure for fixing a B1347/B1348 was for a temperature sensor. From your varying FSM quotes and notes from those with recent experience, I think we need to go with the hands-on experience and note that this *is* a pressure sensor.

A Freon recovery operation involves pumping down the system and will extract any water or air from the Freon as part of the recovery process.

I have seen systems low on Freon that will produce some cooling, perhaps on one side of the car or even just a short length downstream from the expansion valve. These usually ice up at those points when that happens. Gauges tell the tale, and in modern systems the sensors and OBD tell the tale.

I have the 2002 FSM on the 2011 SI DVD, which should be correct[ed]. I'll give the picture and schematic.

1 - A/C Low Pressure Switch

2 - Ignition Control Module (ICM) Bank 1 (for 2002? Really?)

3 - A/C Refrigerant Low Temperature Sensors

This is similar to logan's screen shot. It clearly shows the pressure switch in-line and the temperature sensor on the outside of the Freon line. The pressure switch is on one line going through the firewall and the temperature sensor is on the other line going through the firewall.