[MightyMax]

'91 Silverado, 5.7L 350

Where is the condenser fan located??

On my truck, I have some cooling unit behind the grill....didn't see what he was connected too.
Then my condenser, then my radiator.

So just wondering where the Fan Assembly for him is located.
Is he between the condenser and radiator??
Cause he ain't in front between the grill and condesner.

And I think that is what is causing my High Side pressure on my A/C to jump to 400psi when I cut it on....and it gets really loud.
But when I am driving (and thus air is cooling the condenser) the thing is quiet and seems to run fine. Of course I can't check the pressure then.

 

[2COR517]

The engine driven fan serves as the condenser fan and radiator fan. No separate electric fan.

The extra cooler in front of the condenser is most likely an auxiliary transmission cooler.

 

[MightyMax]

Ok....

Well any ideas as to why my high side is hitting 400 PSI??

Low side is about 40 PSI, if I add more freon, then things really start getting loud at the compressor....

A/C blows cool....but the noise when I am at idle plus the High pressure readings worry me a bit.

 

[2COR517]

Missed that about the pressure before. Most likely caused by a restriction somewhere, first guess would be the orifice tube.

 

[MightyMax]

I was thinking of him as well....
I guess I will be evacuating the system.

I have the tube on hand....I should have replaced him back when I did this all before....oh well.

 

[Bigg Ron]

What is the suction line pressure, if you have a restriction of that magnitude the suction side should be dropping into a vacuum. In fact it sounds like the system could be overcharged and liquid is comming back to the compressor causing your noise, also would like to know what your superheat and subcooling is if your able to keep it running that long

 

[MightyMax]

Well on my low side I read right around 40 PSI.....
Maybe a little lower....
I tried adding in more freon, cause I thought it should be up around 45 PSI.....but that just made the noise at the compressor worse.

And of course on the High Side, with that high pressure, causes some severe heat on the guage connection, so you about burn your hand removing the high side connector.

I guess I could try letting some out to see if that helps first, before emptying the whole system.

But I don't think I used but 3 cans (4 at the most) when I filled him.

 

[MightyMax]

Ok, I released some of the freon....
High side went to 250PSI, Low side dropped to 25 - 30 PSI, compressor stayed on, no cycling.....blew cool in the cab.

Now it ran quiet in the driveway at idle....so I took it on the road.
About 2 miles, when I came to a stop-light, it started to make some noise.....once I started driving again, it calmed down.

I have not re-checked the pressure....will have to do it later.

But I am thinking at this point, it might be the orifice tube.

 

[stew160]

Not sure about your model but many gm trucks condenser fan and radiator fan are one and the same. However they are clutched and the fan rotation adjusts with the engine rpm. Over time the fan clutch weakens and causes poor air flow. A A/A tech told me that this contribute to many compressor failures. Try placing a fan in front of the vehicle and recheck the pressures. Also clear any obstructions to air flow. Seem odd a Radiator flush can help also.

I would think it would be the restriction orifice initially. However if that is the problem, then you may have bigger problems. Something had to contaminate it. Failing compressor or something else. Who knows?
Just food for thought. Hope it helps!

This is my 2nd attempt at a reply. Hope you get one or both.

---------- Post added at 06:26 PM ---------- Previous post was at 06:23 PM ----------

I meant I would not think it is a restricted orifice initially unless you are aware of other issues. Sorry for the Typos

 

[MightyMax]

Ok...
Went out and swapped out the orifice tube....the one in there was gunked up on the side that is facing the condenser....
So put in the new one, put it back together.
Pulled a vacuum and then stuck in about 2.5 cans (12 oz.) of 134a

Now the low side would read around 30 psi, and the high side would get 250, and then climb to around 300....
Started makeing noise at the compressor again, loud noise...

Turned all things off and let it sit for a few min. to cool down....
Then I turn it on and again the pressure started out around 30psi, dropped to about 25 and then settled out around 30.
High side started ~250 and then just kept slowly climbing to 300psi....
Let it run for a bit, the compressor never shut off......never made any noise....
And it blew cool

I think the compressor will need to be replaced.

---------- Post added at 10:39 PM ---------- Previous post was at 09:38 PM ----------

I came across this site (only thing I can find on this issue).....
http://www.autopartsdistributors.net/product/7511348-GM-R-4-New-Compressor/default.aspx?gfid=c6102

It shows an oil capacity of 9 oz.
So does that mean that is how much oil needs to be in the system??

I have not been able to find anything on this model compressor (other than the above site) saying how much oil is supposed to be in the system....

I am thinking now, that when I put this compressor, I may not have added enough oil to it.....and of course now, there is no way of knowing how much I put in.
So I probably have screwed up my compressor.

 

[stew160]

Okay you replaced the compressor, I did not catch that.
When you replaced the compressor:
Did you replace ther orifice and dryer? If so what was the condition of the orifice?
Was the old compressor locked up?
The gunk on the orifice today did it have metal shavings in it? I Hope not
Lots of questions
As far the oil goes. You should have measured the oil from the old compressor and added new back in plus 2 to 3 ounces. Also basically the same for the dryer. If you did neither then you are short on oil and may have damage the new compressor. As both the compressor and dryer are shipped oil free. Also if there is still contamination from old compressor in the system it will damage the compressor also.
I feel like i am possibly the bearer of bad news. Possible total system overhaul.
Good luck! Hope i am wrong. What do I know anyway, I am just full of questions

 

[Bigg Ron]

To check the oil you will need to remove drain all the oil into a cup and measure the qty, it should be close to the 9 oz. there will be some oil in the system, however unless you flushed the system when you replaced the compressor before the system should have already been saturated. If you drain the correct amount of oil out of the compressor then low oil is not the cause of the failure. I would suggest you flush the system when you replace the compressor. be sure to add the correct oil, for 134a POE oil is recommended.

 

[MightyMax]

I did the compressor about two summers ago.

I don't recall the oil amt. originally, because when I got the truck, the previous owners had ripped off the clutch and the low pressure switch.....
The thing was in bad shape.

So I did the accumulator, compressor and put in a new switch....
That was my first time at the ins and outs of an AC system.....so I was very green and didn't understand it all....

I did not replace the orifice tube at that time.....
I added in the amount of oil I thought was right, but as I said, I could never find the amount needed for that system.....so I took a WAG on it.


On Tuesday (the other day), I replaced the orifice tube. He was just gunked up....I didn't see metal shavings....just black gunk.

Most likely I will have to buy another compressor......I have probably killed the one I have now.

I just want to make sure that is what is causing the pressure issues and not something else.

 

[Bigg Ron]

I personally cant see a bad compressor causing an increase in pressure, usally it has bad rings, bearings, or valves which will cause low pressure. The only thing I could possibly think of for the rise in pressure would have something to do with the condensor cooling. It sounds to me like liquid may be comming back to the compressor. At 30psi the temp is around 34f, that is pretty cold, the refrigerant need to warm up before returning to the compressor, please check the superheat, to do this measure the suction pipe temperature at the compressor, compare that to the temp on your gauge, (make sure you have a 134A scale or use a PT chart) you want a 8-12 degree rise in temp.

 

[MightyMax]

Hey Bigg Ron

Can you possibly elaborate on the taking of temp at the compressor to get this info...??
So I make sure I get it right...

Side note here.
I took the truck on a road trip over the weekend, where I was able to maintain about 60 - 65 mph on the highway...
I ran the A/C the whole time.
It did blow cool/cold in the cabin.
I heard some noise coming from him....but not bad.
When I would slow and come to a stop, the noise would kick up....still would blow cool/cold.
When I started to take off again, it would quiet down.

Maybe I should yank the condesner and clean it out??
Or replace??
If cleaning on him is possible, what is the best way to do so??

I think I have roached my compressor though.

 

[Bigg Ron]

Well you should not need to remove the condenser to clean it, car wash spray should do the trick, you need good air flow through the condenser, does the truck run hotter than it did in the past? if so the radiator could also be adding heat to the condenser. To check the superheat, you need a thermometer of some type that you can tape or clamp to the suction side (return) of the compressor (the cold side) check this temperature, compare it to what you read on the low side gauge, the gauge shows PSI on the ouside ring and the different refrigerants on the inside rings, you want to look at the sclae for R134 if you dont have that scale on you gauges the you need to use a pressure temperature scale. You can find on here.http://seit.unsw.adfa.edu.au/coursework/ZEIT4504/HVAC/ZEIT4504_Refrigerants.pdf

Compare the temperatures the temp on the pipe should be between 8 degrees and 12 degerees warmer that what you show on the scale or the PT chart. If your temp is to cold you need to adjust your refreierant.

 

[MightyMax]

For my truck as long as I have owned it, it has always been between 200 and 220
Usually right at 210.


Thinks for clarifying the temp check procedure.
I will see if I can did up a thermometer.

 

[stew160]

You sure the sound is not the ac belt Tensioner?

 

[MightyMax]

I am quite certain it is from the compressor.

Only happens when the AC is on....
Plus it is a noise....I don't know how to explain it.......not grinding per say....but definitely mechanical in nature.

 

[MightyMax]

I think I got it corrected.

I added in some more oil last night and I think it is fine...
I have to take it for a drive and see for sure, but it sounded better in the driveway last night.