ac problems on my tdi

[nb2001]

So I have done some research and not found an exact answer but I have tried alot of simple fixes with no results. My ac blows only the temperature of the air outside, which is fine in the morning but in the afternoon it is 100+ here. The ac light comes on, recirculating light comes on, when I turn on ac I hear the compressor engage, belt seems to be spinning freely, fuses look good in dash, fuses on top of battery and panel on top of battery look brand new, freon levels are good. I had a shop tell me I need a new compressor. Hopefully you guys might know of something different than that. I did buy a clutch assembly and was going to attempt that tomorrow. Thanks!

[gt4494]

Look at the front of the compressor with the engine running and the AC engaged, The complete assembly should be turning not Just the outer part that the belt spins.

Start troubleshooting the easiest parts (and cheapest). Have you checked the freon levels? Systems have a low pressure cutoff that will not engage the compressor if the freon level is low.

If the level is good and the compressor still does not engage disconnect the electrical connection to the clutch and jump it. if it engages it is not the clutch.

[MyOtherRidesAVette]

The "click" is the clutch engaging with the compressor, so it's not likely that it is the clutch. Typical failure is the either the clutch does not engage (a variety of causes), or that it seizes up and trahes not only the clutch and pulley, but the drive belt. It doesn't sound as if it is the clutch, at least not if you are hearing the clicking. You should also be able to observe the inner hub turning (driving the compressor) when engaged. Sounds more like the compressor has failed and is not pressurizing the system. You already said the amount of refrigerant (not Freon, that is a Tradename of Dupont and only R12) is correct. And you've checked all the electrical, wirinig, fuses, switches, etc. Although typically this is done with a meter and not a visual. I put up Automotive A/C 101 in a thread about a "slow to start cooling" system (more than likely a bad compressor also) here. A good read (the link not the thread) to understand the system.
A/C takes a long time to cool, but when it does it works fine.

Unfortunatley when a compressor fails (not the clutch) other parts many times also have to be replaced. Here is a link to a more detailed Automotive A/C 102. This will explain what happens when a compressor fails, and why, when the DIYer only replaces the compressor, he/she may not solve the problem or not be totally happy with the results.
Auto Air Conditioning - Replacing your auto A/C compressor

Although I'm thinking if you have all the proper equipment, to pull down the system, rebuild the clutch, repressurize the system, and run the necessary pressure tests, you know all this. Leads me to wonder why your asking. A/C is not a DIY for anyone that doesn't have experience, AND most importantly the proper equipment.

MORAV

[nb2001]

Morav- I am asking because I dont feel like paying someone $400 for labor to replace this. I usually work on my own vehicles and am young and willing to learn as I go. After looking online it seems a lot of guys replace their own compressor and when I found that sometimes the problem is the clutch I ordered one. Seems like I have checked all of the electrical reasons why it wouldnt be cooling correct? I have heard there is a relay below the battery tray, could this be a reason why its not working? I will check into your 101 I am fearing that it is the compressor as you stated and will need to order that and wait till next week to attempt to replace it. Thank you so much for your reply's.

[nb2001]

by the way, nice to see another vette owner in this forum, I have a white 77 L48

[MyOtherRidesAVette]

Originally Posted by nb2001

Morav- I am asking because I dont feel like paying someone $400 for labor to replace this. I usually work on my own vehicles and am young and willing to learn as I go. After looking online it seems a lot of guys replace their own compressor and when I found that sometimes the problem is the clutch I ordered one. Seems like I have checked all of the electrical reasons why it wouldnt be cooling correct? I have heard there is a relay below the battery tray, could this be a reason why its not working? I will check into your 101 I am fearing that it is the compressor as you stated and will need to order that and wait till next week to attempt to replace it. Thank you so much for your reply's.

I wasn't trying to be a smart ass. It's just that clutches can be rebuilt/replaced if that is the problem, but job shop wise the parts and labor offset the cost of a new compressor with the clutch. AFAIK the compressor still has to be removed from the system, hence the need to evacuate and then recharge the entire system. The NB uses a "thermal expansion valve" on the "low" side and can become blocked or clogged, esp with the breakdown of a compressor[instead of a $5 "orafice" tube as in our Vettes (you never evacuate and recharge a system that has a orafice tube without replacing this because it acts as a filter and can get clogged, and the expense in replacing this is all else that is involved, not the cost of the orifice tube)] . The NB also uses a "receiver-drier" on the "high" side whos' primary function is to separate gas and liquid. The secondary purpose is to remove moisture and filter out dirt. Hence the potential need to replace this. It is also a service item typically changed ever 4-5 seasons, but rarely done until the compressor has to be replaced and the system is down anyway (one of the reasons systems don't perform as well with age). On our GMs, this is the "accumulator". The chief role of the accumulator is to isolate the compressor from any damaging liquid refrigerant. Accumulators, like receiver-driers, also remove debris and moisture from a system. On a GM these, like the orafice are always replaced when the system is down.

I guess what I'm trying to tell you, IF you have to go to the expense of changing the compressor (not just the part, that's bad enough, but the evacuation, flushing, and re-charge of the system - and you don't have the equipment to properly do that, I surmise, and you don't even want to know what it costs) change the thermal expansion valve and the receiver-dryer. Replacing the compressor my get you up and running, but with its' demise these two items may have been compromised and keep the system from operating to its' full potential.

As to the relay you are asking about, I'm sure there is one, and that could be the problem. I am traveling and don't have the Bentley loaded on this computer, nor do I have the paper Bentley with me, so you're going to have to wait for an answer or do some more thread searching.

Won't get a lot of Vette lovers around here, I even had one poster refer to them as "trailer park exotics" in my thread here
No NB2 Here! VW Step Aside! If your into reaaly fast cars!

Kinda' like women and diamonds... Seems the only ones who don't like them are the ones who don't have 'em! Last C3 I had was a '79. Like the C5 way better. Had a partner years ago, who had a C1. 1953, but for me any model year C1 would be fine! C2s okay. Had my C3 (Silver/Oyster interior, glass tops), but would buy a '75 Rag if the condition and price were right. Hate the C4s, always have since the day they were introduced. C6, yeah, nice touch deleting the hide-a-way headlights, but unless it's a ZR-1 probably not doing that; C1 is a far better investment for about the same money.

You might also get a kick out of this thread of mine
Chevy Ads

MORAV

[nb2001]

Morav- you're fine, no worries. Thanks for your posts, they are very helpful. I have some time tomorrow and I am going to recheck everything and exhaust all efforts before tearing into anything. I have loved the 77 for reasons other than its lack of comfort, performance or anything else we measure our vehicles on today. Its just a lot of fun. I had a 94 as my first vette and it wasnt a terrible car, lots of bang for the buck but you get a lot of joe dirt remarks etc. I am hoping for a c5 soon, that is in my opinion the best generation yet. They are a great platform for performance, comfortable and as of now are actually affordable! Thanks again I will let you know what I find out tomorrow.

[MyOtherRidesAVette]

Thank you. And do keep us posted.

Not a lot of comfort in the C3s but I did like the lines till they added the spoiler. '80 or '81 maybe. Know what you mean about the C5s being affordabe! Now! My '01 with 9k miles and every option has a retail value of about $20k, tough to swallow depreciation hit as the cost was nearly $55k. What's that work out 35000/9000? Not quite $4/mile (lol). Can't get rid of it, my four year old grand-daughter has already informed her grand-mother and I that not only does she get the '05 NBC when she turns 16, but the Vette as well. LMAO

M.

[nb2001]

So I got to look at the bug this morning/afternoon. I dont know if this makes any difference but the heater still works great! lol. Anyways when I looked at the compressor, everything seemed to be spinning just fine, clutch etc. So I guess I am looking at a new compressor, drier and expansion valve. It looks like the lines are pressed on and not screwed in so I guess I have to take this to someone with the right equipment etc. I'll catch back up with you guys after about $700-800.

[jason m]

Originally Posted by nb2001

So I got to look at the bug this morning/afternoon. I dont know if this makes any difference but the heater still works great! lol. Anyways when I looked at the compressor, everything seemed to be spinning just fine, clutch etc. So I guess I am looking at a new compressor, drier and expansion valve. It looks like the lines are pressed on and not screwed in so I guess I have to take this to someone with the right equipment etc. I'll catch back up with you guys after about $700-800.

Just for kicks, put a set of guages on it before changing the compressor. If in fact if is coming on you should see it in the pressure difference. I would be interested to see youre pressure readings with it running and in the max ac position. run if about 5 minutes or so and look at the readings again. let us know what you come up with.

[MyOtherRidesAVette]

Ditto to checking the pressure, but I assumed that was how your mechanic came to the diagnosis that is was your compressor in the first place. I just got my Bentley in the mail, and I'm going to read through the diagnostics for the A/C system as soon as I get a chance.

And yes, with the exception of sharing the blower motor the a/c and heat are unrelated. However, as a routine, I run my heat through the a/c system all winter long to keep the a/c system functioning properly. Not running it for months can cause problems. I simply never turn the a/c off unless I am on a long trip in the winter and want to improve the mileage, slightly.

M.