I am at my wits end and hoping someone here can help.
I have a 2002 Dodge Dakota 4WD SXT and recently my A/C Compressor clutch burned out in a big way. I purchased and installed a new compressor, accumulator and fixed orifice. Charged the system and static pressures are good.
Start the truck and only getting about 7-8 VDC to to the clutch.
Not enough juice to pull it in.
Called the compressor mfg and they suggested that the most likely problem is the low pressure switch. Also suggested that this switch may have been the root cause for the initial clutch/bearing failure. Rationale was that they low voltage would cause the clutch to slip which in turn would generate heat, melting the grease from the bearing....ultimately causing a failure.

Suggestion is to unplug the low pressure switch and put a jumper across the plug.
This would be simple enough if I could find the low pressure switch.
The 2000 and 2001 Factory service manuals for Dakota's indicate that the switch is mounted on the accumulator. It is not. (see photo)
Nor is it located anywhere in the engine compartment. I cannot imagine that this switch would be mounted under the dash (could it be?)
There is a 2002 Dakota Manual listed in this forum but it is actually for a 2003 RAM which does not help me.

The 3 lead a/c pressure transducer is easy enough to find (see photo), but I am not sure how to or if I sould even attempt a jumper on this unit. It ties into the PCM and I really dont want cause any additional problems.

Any troubleshooting tips would be appreciated but what I really need to know is
Where is the A/C Low Pressure Switch on a 2002 Dakota? I don't want to bypass it, but I would like to know if it is my problem.

Thanks in advance :-)

 

Pic # 2 is what you want to replace I believe it does two jobs it’s a high side sensor and a low side sensor in one.

Your year doesn’t have a low side pressure switch on the accumulator.

This is only a guess I have been looking at these things the differences in A/C from the 1997 to the 2004 2-nd gen Dakotas and noticed what you described my only conclusion is the one sensor does two jobs in one because it has three contacts.

Replace the A/C COMPRESSOR CLUTCH RELAY it may be bad and its cheap

 

It may be the switch, or the relay, and I agree with 98, it's #2.

Are you measuring voltage with the clutch connected? If so, check the ground too.

 

00DakDan

I have been researching these A/C systems on the 2-nd gen Dakotas do you know what that sensor does as I said it’s a guess as to its function.

The 2-nd gen Dakotas were a mixed bag of changes from 1997 to 2004 they were changing things constantly especially the HVAC system.

I have been collecting different A/C parts from each year from junk yards even they don’t fully understand what Dodge was doing almost every year they changed something with the HVAC system it makes it hard to get the correct used part from a junkyard.

It’s like Dodge used the Dakota as an experimental car/truck those years.

 

98, I agree.

It's not just the HVAC though, lots of things changed. Even within "years" things changed. You really do need the VIN to get the right parts most of the time.

I can't see it being anything more than a combination high/low pressure switch. With a fixed orifice tube you can't do anything to change the metering.

 

Based on member response I think that it is safe to assume that the 2002 Dakotas no longer use the low pressure cutoff switch but instead rely on the High Side Pressure Transducer to act as a system watchdog. Here is what AllData had to say about the workings of this switch:

"A/C PRESSURE TRANSDUCER
This vehicle is equipped with an a/c pressure transducer. This transducer is screwed onto a fitting on the liquid line between the condenser and the high side refrigerant system service port.

The main function of the a/c pressure transducer is to disengage the compressor clutch when the refrigerant system high pressures are too high. The PCM senses a voltage from the transducer and converts it to a pressure. Based on this pressure, the PCM will disengage the clutch at 460 psi and re-engage the clutch at 290 psi . The a/c heater control also uses the pressure value to operate the auto-recirculation function for improved a/c performance under extreme conditions."

AllData Testing and Inspection info:
"Before performing diagnosis of the a/c pressure transducer switch, verify that the refrigerant system has the correct refrigerant charge.

1.Turn ON engine and have a/c selected.
2.Using the DRB-III monitor and record the pressure value as it is sent out from the PCM.
3.Connect the high side manifold gauge set to the fitting on the liquid line high side refrigerant system service port.
4.Compare the DRB-III pressure value to the manifold gauge set reading. The pressure reading from the DRB-III should similar to the reading of the manifold gauge set value.
5.If not, replace the a/c pressure transducer."

BTW AC relay and fuses are all OK

I am thinking that I may just cycle the clutch manually (12VDC dash mounted toggle switch) until I can find a reputable shop to do a proper diagnostic check on the switch and PCM. AllData is not clear on how this switch works as a low pressure cut-off and to confuse things even more, they list a low pressure cutoff switch as one of the component parts of the 2002 model years AC controls.

I'd love to just go ahead and change the transducer, but if at all possible, I want to avoid evacuating the system again. It is not a simple operation nor is it cheap even when I am doing it myself.

Thanks for all of your help and comments. You guys always come through! :-)

 

After a little digging I found out that:
"If the pressure is too high or low (outside of the range 0.451 to 4.519 volts) the compressor won't run"

Assuming they mean the clutch won't engage.

Now I just need to figure out what sized resistor I need to shunt the 5VDC feed down to around 3VDC signal back to the PCM and if the clutch kicks in I'll know I have a bad transducer.

I am not an electrical guru but I am assuming if I ground pin 1, and place the resistor across pins 2-3 I should be able to satisfy the PCM. I just don't know the amount of current flowing through this circuit.

Any ideas what sized resistor I should pick up at the local radio shack? Or am I over reaching and looking for trouble?

 

You will not need to evac the system that switch/sensor has a Schrader valve under it all you will lose is a very small amount of Freon unless the valve has gone bad.

So don’t worry about that as you unscrew it it will pop a small amount then the valve under it will close and now you have the sensor off in hand.

And yes by what you have said that one switch is a dual purpose switch or a high/low switch that talks to the PCM it monitors the pressure in the system

How do I know this I have a (used) one of these, and was trying to figure how it worked and if I could use it myself.

 

So this should be your answer this test

 

The DRB-III monitor is something that I don't have :-( so I thought I would get a little creative. Theorhetically a properly sized resistor or rheostat should do the trick for troubleshooting.
Good news with the shraeder valve as R134a is not cheap and I don't get kicks dumping it into our atmosphere. I've ordered a new transducer and I'll be instaling next Friday when I return from this raod trip.
I'll be back with good or bad news.