AC Questions

[nrramse]

I've had an air conditioner from Classic Auto Air for about 4 years. I've spent way more time working on it than enjoying it!

Two questions:

1. After a while, about 15 minutes of use, the compressor starts to rumble. Any idea what could be causing that?
2. For those of you with the same system, how much refrigerant did you use? The documentation calls for 24 oz.

 

[Broncobowsher]

Never heard of an A/C compressor that starts making noise only after running for 15 minutes. That's strange.
Refrigerant amount sounds about right. If there is a published amount to use, that is what I use. If I change the system (different condenser, different line lengths, etc) or just building a system out of parts I watch pressure and temps and charge according to that.

 

[bronco italiano]

Are you a DIY AC or did you have a shop evacuate/charge the system? Compressor oil correct?

 

[nrramse]

I installed it myself, following instructions that came with the kit and occasionally relying on a licensed HVAC guy at my workplace. The instructions are not very good, which is why I'm here checking the refrigerant amount on this forum.

A few days ago I replaced the condenser which got a hole dug into it by the hood latch. I replaced the dryer too. I evacuated the system for 45 minutes, and then checked the vacuum several hours later to confirm it wasn't leaking. All good.

I intended to put 24oz in it, per instructions, but stopped at 19 when I started seeing frost on the low pressure port. I was worried about it freezing.

At the moment, it's blowing cold but it starts rumbling after a few minutes, at idle. I guess I'll add the other 5 ounces and check again.

The compressor came with oil in it, and I've never added anymore though a shop last year did when they replaced a shrader valve (I don't know why).

 

[ksagis]

Maybe bad bearing in compressor? Does the rumble stop when clutch disengages?

 

[nrramse]

Maybe bad bearing in compressor? Does the rumble stop when clutch disengages?

The rumbling does stop when the clutch disengages. It also seems to go away with RPMs. It's a Sanden compressor with very little time on it.

 

[ksagis]

I dont think I have ever heard fluid flow weirdness converting itself to a rumbling type sound. Seems worth adding some refridgerant and seeing what happens.

Has it always rumbled?

 

[bronco italiano]

What are your pressures in the system when it is running?

 

[nrramse]

I dont think I have ever heard fluid flow weirdness converting itself to a rumbling type sound. Seems worth adding some refridgerant and seeing what happens.

Has it always rumbled?

It has had intermittent rumbling since day 1. In one instance, it went away by tightening the belt but I don't think that's the problem this time. I'll go forward with adding another 5 oz of refrigerant

 

[nrramse]

What are your pressures in the system when it is running? I don't have a gauge set but can get one and will get an answer to this if I still hear the problem after adding more refrigerant

 

[Az72]

I would not add refrigerant until you put the gage set on it. You may have too much in it already. Is it a Sanden or Sanden style compressor?
V belt? 1 or 2? How old is the v belt(s)? Look at the top and back side of the belt real close. Does it seem to shake a little or more when the rumbling starts?
What are the dimensions of the condenser in front of the radiator? Do the instructions state if it is a micro-tube condenser or not? Is it a stock radiator fan?

 

[Broncobowsher]

I'm thinking that the compressor should be changed out before it shells itself and take out everything. A compressor isn't that much compared to dealing with a debris filled system that needs basicly everything or a lot of flushing and hope it is all really flushed.

 

[56f100bbw]

Is it a sanden factory compressor or a sanden style Chinese junk? Look alike , I worked at the factory in Garland, Texas. Back in the 80s The original Sanden are great

 

[nrramse]

What are your pressures in the system when it is running?

I rented a gauge set, and took readings both before and after the rumbling. Before, I saw 9psi and 160psi. After a while, when it started rumbling again, I saw 24psi and 250psi.

 

[nrramse]

I would not add refrigerant until you put the gage set on it. You may have too much in it already. Is it a Sanden or Sanden style compressor?
V belt? 1 or 2? How old is the v belt(s)? Look at the top and back side of the belt real close. Does it seem to shake a little or more when the rumbling starts?
What are the dimensions of the condenser in front of the radiator? Do the instructions state if it is a micro-tube condenser or not? Is it a stock radiator fan?

It is a stock fan. The condenser is 20" wide x 11" tall, "parallel flow". The compressor is a genuine Sanden, model S6626. The single v-belt is new, as are the harmonic balancer and two pullies. The belt looks stable when running, I posted pressures on the previous message.

 

[nrramse]

Is it a sanden factory compressor or a sanden style Chinese junk? Look alike , I worked at the factory in Garland, Texas. Back in the 80s The original Sanden are great

Its a genuine Sanden, model S6626. I'm glad to hear its good quality!

 

[nrramse]

Given that the high side is sometimes getting to 250psi and it seems to coincide with the noise, is it fair to say the high pressure is the cause of the rumbling? I was reading that the expansion valve might be clogged, and am thinking of replacing it.

 

[MarsChariot]

Expansion valves usually groan, whistle, squeal, or even hiss, but I have never heard one rumble. But then I have never heard a rumble from a compressor before, so I know nothing.

 

[ssray]

Given that the high side is sometimes getting to 250psi and it seems to coincide with the noise, is it fair to say the high pressure is the cause of the rumbling? I was reading that the expansion valve might be clogged, and am thinking of replacing it.

I've not heard a system do that either so new to me as well. I was diagnosing a truck a year ago that would cool for a while and then lose cooling the longer it ran. It used a TXV as well and I suspected it was restricted or not functioning correctly. When it was hot (90's) that system would run up around 350 psi when it had been running a while. It would bleed down very slow when shut off. 250 psi isn't necessarily too high if its fairly hot out. I dont know the construction of a TXV but being it is a valve that varies flow, maybe a rare case of fluttering or pulsating in the valve could cause a rumbling sound. The high side pressure would jump around though if that was the case. So thats just a wild guess. The guy I was helping didn't want to open the system up to change the valve so no way of knowing if it was the problem but that was sure my guess.

 

[73azbronco]

my experience, rumbling, to much pressure. lo side low, hi side hi: I'd say receiver dryer needs replacing, new expansion valve, flush the system, evacuate, start over.