I think that I need to change my AC pump. Anyone done it? Easy? Hard?

Advice?

TIA

 

Are you familiar with all the other considerations involved, and you're just asking about the mechanical side of R&Ring the compressor itself?

 

I'm not. What am I looking at?

 

Replacing the compressor itself is probably not that difficult mechanically (I have not done it on a Dodge Cummins, but have done AC replacement on other vehicles in my family fleet). Be warned that it is probably not limited to just compressor replacement - many compressor manufacturers require you to show proof that you replaced (or at least purchased) the condenser and accumulator before they will honor any warranty on the compressor. If the compressor failed, it may very well have plugged the orifice tube with debris - the orifice tube is often crimped in the condenser line on Dodges (at least on 94-98.5 models) and not easily replaceable if at all. I don't know if it's crimped in on '01s. It's also likely that the condenser is partially plugged by compressor debris - modern parallel condensers are not really flushable, as the parallel nature offers the flush liquid a path-of-least-resistance around the debris. A plugged orifice tube or plugged condenser means your system will not function properly after compressor replacement. So, depending on why you think the compressor needs replacing, replacing the compressor is likely not all that needs to be done.

You also need access to a vacuum pump and a set of manifold gauges at minimum, in order to achieve a proper vacuum in the system and to boil off moisture in the system before recharging with refrigerant and to check pressures. A refrigerant scale is highly desirable also, because the charge is really supposed to be weighed in. I bought my 30# drum of R134A refrigerant before you had to have EPA certification to buy R134A drums - you can try weighing in the charge from the small cans, but it will be a headache. You can also go by temperature/pressure charts and be in the ballpark on the refrigerant charge. You also need some good measuring cups - if you only replace the compressor, you'll have to pour out and measure how much oil was in it so you can put that much back into the new compressor. You'll have to decide how far to go on replacing other components and whether to flush all the old oil out or just replace oil based on component replacement (the factory service manual calls out allowances for how much oil is retained in each AC component if that component is replaced by itself). You must have the proper oil charge in addition to refrigerant for the compressor to get adequate lubrication, as the refrigerant circulates the compressor oil throughout the system. If you decide you want to flush the old oil out of the evaporator core, you need a flush gun and an air source (i.e. air compressor).

You need to do some serious reading and research and decide if this is within your capabilities and if you can rent/borrow the equipment or if you're willing to buy it.

 

They should hire you to figure out the election audits.

Thanks for your time.

 

I hope I gave you some insight into what's involved, without it being too intimidating. When I redid my first AC system, I went through a lot of research and reading to understand how the system works, what the components do, and practices and procedures and reasons. A failed compressor may have effects downstream, so to speak, and you need to be aware of that possibility and what to look for (for instance, an orifice tube full of metal shards and "black death"). Fortunately, my brother has done a lot of AC work and my brother in law is an automotive-tech/fleet-mechanic with lots of AC experience, so I have easy access to advice if needed. You can do this yourself, but it will require special tools, willingness to look beyond just the compressor, and the understanding that it's not just removing the old compressor and bolting up the new.

 

Why do you think you need to replace the compressor?

 

When I put the gauge on it, it showed that it had issues. So, I had my neighbor look and listen while I turned the truck on, then the AC. It didn't look, sound, or act differently. We never heard the pump engage, etc. When I googled that, it said that the pump is probably the issue. Without knowing all you said to me, I just figured that I could start installing new stuff until it worked. Now I might not.

 

Throwing parts at your AC system is usually not a good way to find the problem. For instance, if you replace only the compressor but the orifice tube is plugged with debris from the old compressor, you'll restrict the flow of refrigerant and compressor oil. So not only will your pressures be out of line and the system not perform properly, but you'll be increasing wear on the new compressor due to lack of adequate lubrication flow (remember, the refrigerant carries the oil for the compressor).

What kind of gauge readings did you get - high side and low side, and at what ambient air temperature? If the system is sufficiently low on refrigerant charge, the compressor will not engage.

 

Only did the low side reading, and it was about 68 degrees, but I live at 6800 ft. Not sure if that matters.

The reading was in the red, way above desired pressure.Only did the low side reading, and it was about 68 degrees, but I live at 6800 ft. Not sure if that matters.

The reading was in the red, way above desired pressure.Only did the low side reading, and it was about 68 degrees, but I live at 6800 ft. Not sure if that matters.

The reading was in the red, way above desired pressure.

 

I've never seen any reference to altitude affecting system pressures. I have seen one chart that allowed for humidity, but not altitude. I think we can disregard altitude.

Did you use the low side of a manifold gauge set, or one of those low-side-only gauge-on-a-can things? If the latter, accuracy is questionable, to say the least. But it is probably good enough to do some troubleshooting to a point.

Static pressure (non-operating) will be the same on low and high sides, and low-side pressure should drop below static pressure when the compressor is operating ( high-side will rise). You said that you could not detect any signs that the compressor was operating. If the compressor was engaging, you would see low-side pressure drop while the compressor is operating and rise when it cuts off. Did you see any signs of this? If not, I would first verify that the compressor is actually getting 12V to both sides of the connector. Be sure to check the wiring - I just saw a thread on another forum where the thread starter said his compressor ground wire was caught under the suction-discharge manifold connection and cut.

Here's a link to a typical R134A temperature/pressure chart. Based on that, I would estimate low-side operating pressure of 28-33 PSI at 68 degrees air temperature with a proper refrigerant and oil charge.
https://www.jamcoautoparts.com/syste...shootingchart/

 

I will check the wiring, and saw no difference in pressure when the running truck had the AC turned on. I was using the gauge on the AC refill can. I don't have any other gauge.

 

It sounds to me like the compressor is not coming on at all. You need to verify that the compressor is actually getting electrical power - do you have a 12V test light or multimeter? A multimeter is good to verify that you're getting both 12V positive and ground to the compressor clutch, but a test light that could put a few amps load on the circuit (3-4 amp draw should be sufficient) will give some comfort level that the wiring is intact enough to support the electrical load of the clutch. If you can't do the test light, just do the multimeter check for voltage at both terminals on the connector for now.

Are your tach and charging system working ok? Cruise control? OD if automatic trans? If those are not working, you might have a bad crank or cam position sensor. My '96 only has an engine speed sensor - RockAuto shows crank and cam position sensors for your '01, so will someone please chime in on the presence of crank and/or cam position sensors on the 24-valves? Lack of engine rotation/speed signal means the compressor clutch receives no voltage, so that means the engine must be running for the test mentioned above.