A/C Clutch Not Engaging

I have already searched the forum for an answer to my question and came up with nothing.

My climate control unit has been fixed and the hot/cold switch functions properly. When I turn on the front A/C (push snowflake button) I do not get cold air. I was considering checking the charge but decided to see if the clutch was engaging first. It does not engage when the A/C is on. Additionally, my rear A/C compressor clutch does not engage either.

Let's start with the front A/C. Are there common reasons for the T1N sprinter front A/C clutch not engaging? From the wiring diagram it appears that a wire goes from the magic climate control box to the A/C compressor. So I will likely pull that off at the compressor and determine if I get a voltage when the A/C gets turned on. But I want to reach to others with more experience to see if there are common problems.

Seems suspicious that both compressor clutches do not engage.....almost like they are related.

Thanks in advance for advice.

Other important details: I bought the van about a 1.5 months ago and the climate control unit did not work and a multi-pin connector behind the gauge cluster was unplugged. After addressing both of these items the A/C light came on and the rear blower motor worked. I do not know the history of the van and the A/C has never worked for me, so I do not have a great benchmark for functionality.

You might get more responses if you put your model and year in your signature.

Do not get fooled by the reasoning that both systems are related. You can tap the front of the compressor clutch with a screwdriver handle and se if there is a clutch gap problem. You can check for DTC's of the AC module and see if there are any codes set.

Run 12 volts to the compressor from the battery's positive terminal when the engine isn't running. Is the clutch clicking/grabbing?

Rickpcmp3 said:

Run 12 volts to the compressor from the battery's positive terminal when the engine isn't running. Is the clutch clicking/grabbing?

Click to expand...

Great idea. Is it safe to do so?

I think the sprinter doesn't let the compressor run if it sees too low of refrigerant, btw.

Dougflas said:

You might get more responses if you put your model and year in your signature.

Click to expand...

04 2500 Dodge 140" Passenger with Rear A/C

SneakyAnarchistVanCamper said:

Great idea. Is it safe to do so?

I think the sprinter doesn't let the compressor run if it sees too low of refrigerant, btw.

Click to expand...

My mechanic friend suggested this. He also said that it might be a bad pressure switch??

Dougflas said:

Do not get fooled by the reasoning that both systems are related. You can tap the front of the compressor clutch with a screwdriver handle and se if there is a clutch gap problem. You can check for DTC's of the AC module and see if there are any codes set.

Click to expand...

When tapping should I look for play between the clutch and the pulley as an indication of "clutch gap"? Maybe the more important questions is "what is clutch gap?". Is it a condition where there is too much of gap in the radial direction between the clutch and the pulley?

AC clutches have an air gap between the the rotor and stator. The magnet in the clutch overcomes this gap, and brings the two together, making the compressor spin. If the gap is to large the electromagnet in the clutch can't do its thing.

Low refrigerant is a common cause of no clutch engagement. Since neither clutch is engaging, and you have separate front/rear systems, low refrigerant is less likely.

The T1N AC head unit has a history of cracked solder joints on the AC clutch relay located on the circuit board. (see thread below).

https://sprinter-source.com/forum/showthread.php?t=47889

Midwestdrifter said:

AC clutches have an air gap between the the rotor and stator. The magnet in the clutch overcomes this gap, and brings the two together, making the compressor spin. If the gap is to large the electromagnet in the clutch can't do its thing.

Low refrigerant is a common cause of no clutch engagement. Since neither clutch is engaging, and you have separate front/rear systems, low refrigerant is less likely.

The T1N AC head unit has a history of cracked solder joints on the AC clutch relay located on the circuit board. (see thread below).

https://sprinter-source.com/forum/showthread.php?t=47889

Click to expand...

Thanks for the link. This solder joint is buried in the ATC which has been refurbished. The shop that rebuilt it said that they check for a variety of common failures. And so for now, I am going to assume that this is not it.

I just checked the wire going to the A/C compressor and it had ~12V whether the A/C switch was on or off. Is there constant power to the compressor until the A/C is turned on? That seems backwards to me.

I just tried disconnecting the refrigerant pressure sensor. When I did this the aux fan came on and the compressor clutch engaged. I think this is good news, but not sure how to interpret it. Maybe it means that I am out of refrigerant or maybe it means that I need a pressure sensor.

Make sure you're using either a test light or an analog meter to measure the 12 volts.

SneakyAnarchistVanCamper said:

Great idea. Is it safe to do so?

Click to expand...

Safe so long as you don't ground the wire anywhere on your way to touching the pin inside the connector for 12V on the compressor.

Dougflas said:

Make sure you're using either a test light or an analog meter to measure the 12 volts.

Click to expand...

Exactly, that 12V your seeing may not in fact really be 12V when loaded. Again, and this is the last time I say it. Try to manually engage your compressor clutch with the engine off by supplying 12V straight from the battery. If it engages, your harnesses 12V supply to the compressor is compromised.

I figured out that the system was low on refrigerant. Unplugging the pressure sensor was key for arriving at this conclusion. When the sensor is unplugged the A/C compressor clutch engaged. I did some reading online and learned that the purpose of the pressure sensor is to ensure that the compressor does not run if the system has too little pressure or too much pressure. Knowing this, I did not leave the sensor unplugged for long so that I did not damage the compressor. Anyway, I decided that the sensor was either bad or was functioning properly by sending a signal to the ATC that disabled the compressor due to an over- or under-pressure.

Now, the workshop manual provides some guidance on how to check the voltage from the sensor that goes to the ATC module. There is a table of voltage readings that correspond to different conditions. Zero volts means the sensor is not working, a voltage between 0 and ~0.45 indicates lower pressure, a voltage between ~0.45 and ~4.5 indicates normal pressure, and anything above 4.5 volts is considered high pressure. The problem is that the manual says you need a scan tool to read this voltage, which I do not have. I decided to probe the signal wire on the connector that attaches to the sensor to see if I could read the same voltage. On my sensor plug this was the middle wire. It read 0.36 (considered low pressure).

I went to the local auto parts store and purchased a DIY refrigerant charging kit. While charging the system I monitored the voltage signal from that same middle wire on the sensor plug and watched increase as more refrigerant was added.

The system now blows cold air. I will recheck in a few weeks for signs of a leak.

You really should get a gauge set on the van for a proper charge. Sprinters have an expansion valve and accumulator, so they will run okay a few ounces high or low.

Also, avoid the cans that come with oil and/or stop leak. They could very possibly cause compressor lock up, or other issues.

Do use refrigerant with UV dye. Unless you find the leak, your are just going to keep pissing R134A into the air. Unless the leak pulls some oil with it (it may not depending on where it is). There will be no obvious leak signs. If you have dye in the system, a UV light will readily show the leak location.

I strongly suggest, that once you find the leak, you charge the system properly. To do this yourself, you need a scale (to weigh R134A bottles), vacuum pump (with fresh oil), and a gauge/manifold set. Amazon has these for reasonable prices, some auto parts stores will rent them.

If you don't wan't to pay the $$ for the right tools, take it to a Pro, and have them evac and do a weighted charge with their refrigerant machine.

The Pressure sensor is a failsafe, and is not indicative of a proper charge. Just cause the sensor is happy doesn't mean your compressor/belt drive isn't being stressed, or your clutch could be rapidly cycling due to low evap temps etc.

The lower part of the condenser is a fairly common leak point on T1Ns, as it is fairly unprotected from road debris.

If you need to have the system open to the air in order to replace/repair the leaking part, you should replace the receiver/dryer. Fresh O-rings at most of the major junctions is a good idea (assuming the B-Nuts aren't seized.

Midwestdrifter said:

You really should get a gauge set on the van for a proper charge. Sprinters have an expansion valve and accumulator, so they will run okay a few ounces high or low.

Also, avoid the cans that come with oil and/or stop leak. They could very possibly cause compressor lock up, or other issues.

Do use refrigerant with UV dye. Unless you find the leak, your are just going to keep pissing R134A into the air. Unless the leak pulls some oil with it (it may not depending on where it is). There will be no obvious leak signs. If you have dye in the system, a UV light will readily show the leak location.

I strongly suggest, that once you find the leak, you charge the system properly. To do this yourself, you need a scale (to weigh R134A bottles), vacuum pump (with fresh oil), and a gauge/manifold set. Amazon has these for reasonable prices, some auto parts stores will rent them.

If you don't wan't to pay the $$ for the right tools, take it to a Pro, and have them evac and do a weighted charge with their refrigerant machine.

The Pressure sensor is a failsafe, and is not indicative of a proper charge. Just cause the sensor is happy doesn't mean your compressor/belt drive isn't being stressed, or your clutch could be rapidly cycling due to low evap temps etc.

The lower part of the condenser is a fairly common leak point on T1Ns, as it is fairly unprotected from road debris.

If you need to have the system open to the air in order to replace/repair the leaking part, you should replace the receiver/dryer. Fresh O-rings at most of the major junctions is a good idea (assuming the B-Nuts aren't seized.

Click to expand...

Too late. I already put it in. I guess I will see what happens. Thanks for the advice.