AC compressor lit up, AC questions

[shifty]

Reckon I need to fix this. I survived last summer but don't want to again. Know this - I'm not an AC guy.

Gist: 98 Sierra, L31 5.7, A/C is shot. I know it's a leak. Suspect It's the compressor.

Piped in one can of R134a. Worked great for an hour. Then dead. Piped in R134a with dye to check for leaks. 30 minutes later, dead. Busted out the light and I see the entire housing of the compressor is freckled like a Christmas tree, front of housing, back of housing, and a lot along one of the seams. See pics, best I can do with two hands, special light, phone with glasses over it.

Found the correct AC Delco compressor/clutch for $200 on sale. it looks like it's just a few bolts and bracket out to swap. Worth doing myself?

If yes, what else is necessary to replace, orifice tube and receiver/dryer?

Or just "take this one in to a reputable shop"?

(I have a Hayne's manual, if it matters. But didn't seem too helpful, only shows clutch replacement)

Figured I'd replace serpentine at same time. Truck is getting close to 90k miles and it's got the original belt. If I do it myself, I figure I can save a couple hundred.

[Richard]

If system is flat or has very little refrigerant you could save some by replacing the compressor yourself. If hoses are original would be wise to replace them as well as all o rings. While you may be able to purge the system, to recharge correctly when completely flat (no pressure) a vacuum needs to be pulled on the system to get all the air out. So unless you have the right tools leave that to the professionals.

[Kudzupatch]

I did the conversion when my compressor died and while it is not hard, but you have to have a vacuum pump to pull all the moisture out of the system and you really need a set of gages to make sure everything is working right.

And yes, you need to replace all the other items. They will not honor the warranty on the compresor if you don't. Plus there is some good reasons to replace all the other items.

[shifty]

Thanks for the info y'all. As much as I prefer to work on my own stuff, this sounds like one of those "best to leave to the experts" situations.

I'm still trying to figure out what the hell is up with the compressor lighting up like that. I mean, I clearly see near the lower seal (I couldn't photo) the compressor is leaking. Is it actually the oxidation of the chassis causing it to illuminate like that? It's not like the compressor itself would "sweat" dye, eh?

[speedygonzales]

There are a few things you absolutely must do and others you should do.

First if you don't replace the orifice tube AND flush all the lines and evaporator and condenser, you're wasting time and you won't get a warranty (unless of course you lie about it). You have to replace the accumulator. It has dessicant in it. This is also the place to put in the remaining amount of oil that won't fit in your compressor. More about that in a moment.

You should replace all the O-rings and or washers that contain rubber like material.

Most O'Reilly's stores carry the spray can for flush, the manifold gauge set and vacuum pump to borrow for FREE. You pay for the tools upfront but you get every dime back when you return it. The flush fluid you must buy obviously.

Look up how to flush the system and you're half way there. Probably a million videos on youtube.

You have to put the correct PAG oil at the correct amount in the compressor. Documents that come with it should tell you that. Since all of the amount recommended will not fit in the compressor, you place the remaining amount in the accumulator.

After the system is buttoned up, you vacuum it down. The job is a little bit harder to do if as most of us, you don't have a vacuum micrometer. This tells the amount of vacuum way below what the manifold gauge tells you. If while you're doing the vacuum, you get below 500 micro (don't remember the units) that automatically tells you that the system has no leaks as you could not obtain 500 if the system was leaking.

However all you and I have is the manifold gauge set. So like the rest of us you put the vacuum pump on it and just let the pump run for a couple of hours. Then you shut the pump off and observe the gauge for a few hours to be sure the vacuum is not going down/up(read leaking). You should have pegged the gauge and it should have stayed there for a few hours after the pump is shut off. Search youtube for this process also.

Now it's time to put the refrigerant in and you want to start by putting in the correct amount by weight for the system. A label near the engine tells you how much. Now you can start up the AC system and observe the pressures on both sides. With a little knowledge (again on youtube) you can then dial in the correct pressures by adding just a small amount of refrigerant.

2 items of interest: If you have a leak when vacuuming the system, you can easily find the leaks if you then pressurize the system with compressed air but be careful the pressure you obtain. Don't over do it. Obviously at that point you could use soapy water to find the leak.

Second, although some might warn against it, I think it's a good idea to put die in the system when you charge it. Eventually ALL systems leak and if it's already in there, it's a piece of cake to find.

consider the next 2 things. One, a Sanden compressor over all others. They are oem on many vehicles (not for you and I) but they make the best compressor hands down. I got one for my vehicle some years ago and it is fantastic.

The other consideration is going one step cooler on the orifice tube. Ask around about this. Several people swear by doing this. I don't remember the color of the orifice tube that came in the vehicle originally and also don't remember the color of the orifice tube that is one step cooler but now is the time to ask the question before you button the system up.

Good luck.

[shifty]

Holy crap. That's awesome, speedy! thanks for the big picture of what I'm up against.

Last time one of my vehicles with AC was on the fritz turned out to be a bad compressor or clutch, dealer reco'd using Sanden on the replacement. Was on a '99 VW GTI.

I'm usually a Delco guy myself but after suffering from their issue with spastic oil sending unit used on the L31 and reading how common it is for these trucks, my leaf is about ready to turn over.

[speedygonzales]

ALL the oil sending units are plastic. Don't hold that against GM. How many years did you have on it before it failed? They usually go that way regardless of how they are made. Not that GM's compressor is bad, I just know of Sanden's reputation and have one myself. My wife used to have a Durango and that had a factory Sanden that never failed. Unfortunately the evaporator coil did. Ugh what a job that was.

Here is the tools for your job

flush spray can

manifold gauge set

vacuum pump

Not all stores have these available so call first to ask. They can usually transfer the tools they don't have to their store on a temporary basis from the stores that do, if the other stores aren't close to your location.

Most often when a compressor fails (in my case it didn't fail but still put filings in the orifice tube) it will put metal filings into the system. This is why you have to replace the orifice tube and flush the system. Look closely at your orifice tube when you remove it. It will have metal filings in it. I can just about guarantee it.

Also I never do my own charging. I've done the complete job except for vacuuming and charging. By that I mean, I flushed EVERYTHING, replaced all components and hooked the system back up. Then took the truck to a shop to have them vacuum and charge it. However if you got to that point on your own, the rest is not that hard.

So you could buy and replace the necessary components. Flush out the ones that need to be flushed so you know the job was done correctly. You would only need the flush spray can and flush fluid listed above (as long as you have a compressor).

The most important point is that the vacuum holds for hours before you charge it.

Finally here is one of many links to a sanden BOLT IN replacement unit like I got. The Sanden part number is 4440.

sanden compressor

Another thing I just remembered. The hoses that connect to the compressor have a schrader valve that often (I mean a lot) sticks. It would be a good time to replace that set of hoses. If you fill the system and that valve sticks, you cold loose a lot of refrigerant.

All the components you need are available at O'Reillys. The hose set, the accumulator, the O-rings and washers, R134 and more.

Incidentally I wanted you to see the micron gauge I was speaking about with regard to vacuum.
micron gauge

As I mentioned before, if you achieve 500 microns or lower while doing the vacuum, there is no question you DO NOT have a leak in the system.

Write us back and let us know how you made out please.

[Kudzupatch]

Oh yea. I remember having to do all that now that I read this. Been 2.3,4,?years and forgot most of the steps now. But that is exactly what I did and it has worked perfectly. Actually the first compressor failed in warranty but because I followed all the steps they replaced it. Been fine every since and I was lucky enough to have a buddy with a vacuum pump. Made from an old Ford(?) AC compressor.

[shifty]

I'm going to give this a go over the weekend! I was contemplating spider upgrade and oil sender replacement (at same time) but air is more important to me at this point.

[shifty]

So, compressor and serpentine belt arrived today. On a whim after work, I got some soapy water, sprayed the compressor down, fired up the truck, forced the clutch to kick on and watched it bubble. Totally blown.

I think I'm going to take a sick day and tackle this tomorrow. Wish me luck!

[speedygonzales]

Hope you got an accumulator
accumulator

and an orifice tube

orifice tube

[shifty]

Based on your input above, I sourced out a shop to vacuum & charge for me. Shop owner is in his 60s, close friend of one of my close friends, he only does domestic, he's a GM fanatic, he actually drives our trucks.

He told me if I replaced the accumulator and compressor he'd do the finishing work for $150: Replacing the high and low side ports because he mentioned the rubber in the OEM ones often gets damaged when you hook gauges up to it, vacuum down and test for leaks, if all was OK he'd charge it up after.

Sounded like a fair deal to me, I'm already saving $150 getting the compressor on sale (went Delco, Sanden was 2x more). So I got the accumulator from the big box store when they opened this morn and got to work.

He told me in his professional experience, he wouldn't bother with orifice tube on these trucks unless the compressor grenaded and there was clear evidence of particulate risk, but he would confirm everything before vacuuming down then make sure there are no other leaks. He mentioned the OEM orifice tube - which my low-mile truck has - can be a pain this far along due to oxidation (I forgot where he said oxidation was - housing? dunno) and to skip it.

So, I got the compressor and accumulator in, replaced the serpentine belt, rings, tightened everything up, and dropped it off. He's offered 2yr guarantee in writing I won't have any problems (I was worried about the orifice tube) and if the compressor does fail, he'll call the shop personally after diagnosing at no charge.

The guy was recommended by a close friend, I trust him by proxy, although we've all been screwed over like that once or twice. Thing is, he's aware if he screws me over, it's going to impact that relationship.

I'll be picking up the truck at the end of the day. He already called to confirm: He confirmed no leaks on evaporator, and he's got the rest of the system under vacuum right now for about an hour and all looks good.

I really wouldn't have been confident about this without your help, speedy. Thanks! (I'm saving at least $200-300 at this point, best I can math)

[shifty]

Very happy to report I HAVE COLD AIR AGAIN. Super happy I won't be spending an entire summer sweating my ass off again! WOOHOO!

Now to deal with the oil pressure sender and I guess deal with MPFI spider too.

[pwdcougar]

Originally Posted by speedygonzales

ALL the oil sending units are plastic. Don't hold that against GM. How many years did you have on it before it failed? They usually go that way regardless of how they are made. Not that GM's compressor is bad, I just know of Sanden's reputation and have one myself. My wife used to have a Durango and that had a factory Sanden that never failed. Unfortunately the evaporator coil did. Ugh what a job that was.

Here is the tools for your job

flush spray can

manifold gauge set

vacuum pump

Not all stores have these available so call first to ask. They can usually transfer the tools they don't have to their store on a temporary basis from the stores that do, if the other stores aren't close to your location.

Most often when a compressor fails (in my case it didn't fail but still put filings in the orifice tube) it will put metal filings into the system. This is why you have to replace the orifice tube and flush the system. Look closely at your orifice tube when you remove it. It will have metal filings in it. I can just about guarantee it.

Also I never do my own charging. I've done the complete job except for vacuuming and charging. By that I mean, I flushed EVERYTHING, replaced all components and hooked the system back up. Then took the truck to a shop to have them vacuum and charge it. However if you got to that point on your own, the rest is not that hard.

So you could buy and replace the necessary components. Flush out the ones that need to be flushed so you know the job was done correctly. You would only need the flush spray can and flush fluid listed above (as long as you have a compressor).

The most important point is that the vacuum holds for hours before you charge it.

Finally here is one of many links to a sanden BOLT IN replacement unit like I got. The Sanden part number is 4440.

sanden compressor

Another thing I just remembered. The hoses that connect to the compressor have a schrader valve that often (I mean a lot) sticks. It would be a good time to replace that set of hoses. If you fill the system and that valve sticks, you cold loose a lot of refrigerant.

All the components you need are available at O'Reillys. The hose set, the accumulator, the O-rings and washers, R134 and more.

Incidentally I wanted you to see the micron gauge I was speaking about with regard to vacuum.
micron gauge

As I mentioned before, if you achieve 500 microns or lower while doing the vacuum, there is no question you DO NOT have a leak in the system.

Write us back and let us know how you made out please.

Annnnd another great write up!

[speedygonzales]

Thanks to both of you for the compliments. Glad it worked out.

[shifty]

PS - almost forgot the money shot! Took this after changing the oil yesterday. Little before/after shot.