Aircon Probs...

tracktoys

Loves his Sprinter
Hi all

Few aircon issues I am trying to sort...

Aircon doesn't work.

Red light does come on at the dash.

12v applied to compressor does engage the clutch.

Unsure on refridgerant level, although there is enough in there to give a quick psssht on a valve.

Compressor Cable - I have 10.5 volts here, with ignition on, with the aircon switch in EITHER position - however clutch is not engaging. This doesnt seem correct - surely should have no voltage there when off?

The relay in the heater panel does click in and out.

When reinserting the panel electrical connector (ie not entirely seated) the auxilliary fan does kick in as some connections are made, and others aren't.

External Temp Senser doesnt work (not sure if this would cause an issue, ie, aircon not allowed at -40 degrees C)

Blower motor only works on 4 - need a new resister pack (again not sure if this would allow the AC to work or not)

Main AC fuse is OK. As is Aux Fan relay under seat.

Any help greatfully appreciated - I have an AC man coming out to check the levels and pressures this weekend.

:thinking:

:bow:
 

jmoller99

Own a DAD ODB2 Unit.
This is a common issue. You will get pressure (ie. a 'Psst') even if there is practically no R134a in the system.

NOTE: NAFTA information - This info may not be the same for other locale Sprinters

A quick and simple procedure is to get a large bottle of R134a and a fill kit with a gauge on it (these are not that expensive at any auto parts store). Read the instructions that came with it!!

Find the low pressure side (the narrow tube) fill port. Screw the R134s fill bottle to the hose and connect the other end to the low pressure fill port (it will only fit that one - the high pressure fitting is too large). Start the engine and turn the AC on full blast. Pierce the fill bottle and then unscrew the piercer to allow R134a to flow. Keep the can upright and let the AC suck in the Freon. The can will get cold, as will the low pressure side of the line. The High pressure side will get very warm. Watch the guage. This will take a while. It will never fully empty the R134a bottle, but it will get most of it.

You don't want more than 40 psi in the AC system - over filling the AC is a very bad thing to do. You can always purge (from the low pressure side) as needed.

If that does not address the issue, You should take it to an AC place.

I've recharged 3 Sprinters (including my own) this way - all had symptoms similar to yours.

It may take a few hours for the full cooling effect to take place - run the AC!

---

The Status of the Blower Resistor pack won't affect the AC operation.

You might also have bad connections at the fuse boxes (I had this issue). Clean them one at a time (takes a while) - under the drivers seat and under the steering column - note if you have the stock radio, you will need the code to re-enable it (at least for the 2002 - 2006 models).
 
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tracktoys

Loves his Sprinter
Thanks - that puts my mind at rest that the recharge wont be wasted money. I had looked at the self recharge kits, and for the cost of a mobile guy, it didnt seem worth the saving.

I have had a look through the parts diags today, didn't suspect the blower resistor, but needed one anyway so ordered that..

However - looking at all the of temp sensors, and the service manual, I cannot help but think the ambient temp sensor has something to do with the system, it flickers between -40 deg C and nothing, so maybe if the AC thinks its too cold, it wont allow it to work - certainly makes sense, but again as before, I need one, so have one on order. It is also included on the electrical schematics for the HVAC system, so must be linked - surely?

Should arrive Saturday AM, so will get those fitted, along with a new AC drier, as I know they have a finite life.

So - the only remaining item is a duff compressor, although I know it fires up, and the pressure transducer. Which will be annoying if it is that, as it means another recharge. Grr.

Main aux fan defo works, I guess I'll know more when the AC man checks the pressures!

Wish me luck!

Don't know why I am too bothered - this sunny spell we are having here in the UK should only last another week :idunno: but I hate having a van with bits that don't work.

Once this is done, the only remaining item is the Heater Booster (although I think I had the pumps the wrong way round as I was voltage checking - oh and one is definately stuck as its RED HOT after 30 seconds of running :censored: but I will save that for another post!
 
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bc339

New member
If you don't have the '06 service manual, download a copy - it should be in the database section. It has a good section for the air conditioning.

Here's the description of the pressure transducer and the reason why you are seeing a voltage:

OPERATION

The A/C pressure transducer monitors the pressures in the high side of the refrigerant system through its connection to a fitting on the liquid line. The transducer will change its internal resistance in response to the pressures it monitors. The ATC control module provides a five volt reference signal and monitors the output voltage of the transducer on the transducer return circuit to determine refrigerant pressure. The ATC module is preprogrammed to respond to this and other sensor inputs by controlling the operation of the air conditioning compressor clutch and the auxiliary radiator cooling fan to help optimize air conditioning system performance and to protect the system components from damage. The A/C pressure transducer input to the ATC module also prevents the A/C compressor clutch from engaging when the ambient temperature is below 0.556° C (33° F) due to the pressure/temperature relationship of the refrigerant.

The A/C pressure transducer is diagnosed by performing the ATC Function Test using the DRBIIIt scan tool. Refer to Body Diagnostic Procedures. The A/C pressure transducer cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.

DIAGNOSIS AND TESTING A / C PRESSURE TRANSDUCER

The A/C pressure transducer is tested using a DRBIIIt scan tool. Refer to Body Diagnostic Procedures. Before testing the A/C pressure transducer, be certain that the transducer wire harness connections are clean of corrosion and properly connected. For the air conditioning system to operate, an A/C pressure transducer voltage reading between 0.7 and 4.56 volts is required. Voltage outside this range indicate a low or high refrigerant system pressure condition to the ATC control module. The control module is programmed to respond to a low or high refrigerant system pressure by suppressing operation of the compressor.
Refer to the A/C Pressure Transducer Voltage chart for the possible condition indicated by the transducer voltage readings.

Voltage Possible Cause
0.0

1. No transducer supply voltage from ATC control module.
2. Shorted transducer circuit.
3. Faulty transducer.

0.150 to 0.450

1. Ambient temperature below 10° C (50° F).
2. Low refrigerant system pressure.

0.451 to 4.519

1. Normal refrigerant system pressure.

4.520 to 4.850

1. High refrigerant system pressure.

5.0

1. Open transducer circuit.
2. Faulty transducer.


Bruce
 

tracktoys

Loves his Sprinter
Thanks for that, already read that and found it useful!

Replace blower resistor and ambient temp sensor this morning, aircon recharged and is working great, was empty!

Aircon guy is concerned about the fan, expected it to come on, but hasn't.

I know it works as I have tested it... What is the criteria for the fan switching on?
 

tracktoys

Loves his Sprinter
Forum search is my friend!

As suspected AC pressure is the trigger, AC guy saw 16 bar saw 235 psi high side, obviously van was in workshop so engine didn't really make any temperature. According to other posts I'd approx 245 psi when it kicks in, so all looks good this end, will see how it goes but at the moment it's icy cold...
 

lobsterfearme

New member
Thanks! Ac recharge did they trick! Had only cool on passenger side and now after oiling all adjustments for vents, replacing air filter and the trip to auto zone it works great! Now to re assemble the dash! Thanks!
 

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