Checking AC

DWBOX2000 · 08-01-2023, 02:53 AM

What do I need to check that my ac on my 99 boxster works? Is it just a pressure gauge I can get from harbor freight or is it more involved? I bought the car in March and believe I forgot to check when I bought unfortunately. Whether I sell or keep, I should probably take care of.
Thanks.

asphaltgambler · 08-01-2023, 03:13 AM

Is it cooling now? If not, does the HVAC blower fan work? Does the indicator light for A/C come on when selected?

1990C4S · 08-01-2023, 04:27 AM

Check your vent temperatures first. If they are good, then assume the AC works fine. You should be able to get roughly 20F below the ambient temp.

If the temps are not low enough, a cheap set of gauges will help you diagnose what's wrong.

1990C4S · 08-01-2023, 04:38 AM

Check your vent temperatures first. If they are good, then assume the AC works fine. You should be able to get roughly 20F below the ambient temp.

If the temps are not low enough, a cheap set of gauges will help you diagnose what's wrong.

GH85Carrera · GH85Carrera's Garage

Quote:

Originally Posted by 1990C4S

Check your vent temperatures first. If they are good, then assume the AC works fine. You should be able to get roughly 20F below the ambient temp.

If the temps are not low enough, a cheap set of gauges will help you diagnose what's wrong.

Only 20 degrees ??

So in 100 degree heat only 80- degree air? I don't think that is very good. My old 85 911 with the full 4 condenser system from Griffiths will blow 37 degree air on me on the hurricane speed blower when it was 107 degree.

You should get 35 to 40 degree air regardless of outside air temp.

DWBOX2000 · 08-01-2023, 04:58 AM

No ac, fan works and ac light turns on.
What is the tool (s) called?
Thank you everyone

billybek · billybek's Garage

Can you hear the compressor kick in when you enable A/C at the control?

Could be anything from the clutch, compressor, metering device or out of juice.

Leaks should be repaired before re-charging.

A charging manifold or gauge set is what you are looking for. Probably R-134a refrigerant.

GH85Carrera · GH85Carrera's Garage

Quote:

Originally Posted by billybek

Can you hear the compressor kick in when you enable A/C at the control?

Could be anything from the clutch, compressor, metering device or out of juice.

Leaks should be repaired before re-charging.

A charging manifold or gauge set is what you are looking for. Probably R-134a refrigerant.

This. Your problem could be just about anything. You will need to diagnose the problem. One day my El Camino AC just stopped blowing cold. I opend the hood and the connection to the compressor had come off enough to not make a good connection. Push it back on, and ice cold air again.

It is much like the endless posts in the tech site of "My car will not start" and it can be a myriad of different causes.

Zeke · 08-01-2023, 06:22 AM

Don't check your AC if you don't need to. I have R134 gauges and hooked them up to read pressures. The Schrader valve does not need to be disturbed or it may start to leak. Next time I drove the car the AC was empty. This won't happen often but it can so why take a chance? If it works, don't fix it.

fastfredracing · 08-01-2023, 06:29 AM

I agree with Zeke here, but if you have no ac operation, checking the AC fuse is first, then connecting gauges is next .
When you do connect to the service ports, only turn the knobs down far enough that you have opened the schrader valves . I usually watch the gauges and as soon as the needle moves, I stop turning .
I have damaged a few schrader valves like this, and also, sometimes, just disturbing them causes them to leak .

DWBOX2000 · 08-01-2023, 06:35 AM

I’ll look around. Not sure what I’m looking for but maybe the Bentley book will help. Seems I always try to fill first just to waste 50 bucks when it doesn’t hold. Thanks.

Bob Kontak · Bob Kontak's Garage

Quote:

Originally Posted by fastfredracing

I agree with Zeke here, but if you have no ac operation..............

You need to get to where the compressor clutch engages magnetically with the compressor pulley. That takes a working fuse/relay and enough pressure in the system to get the ok from the low pressor sensor to engage. The car needs to be on and the AC needs to be on.

You can buy a $10 can of R-134 at Walmart and put that in to get the minimum pressure but you could also have a completely full system with a blown fuse that wont allow the clutch to engage. That's bad to overfill.

Just go slow and ask questions.

When you buy a gauge set get a vacuum pump too. Habor Freight has a $20 vacuum pump that is adequate that works with your garage air compressor. The electric ones are better and frankly buy the $100 one vs the cheaper one.

fastfredracing · 08-01-2023, 06:49 AM

You need a set of gauges . You should see somewhere around 70 -100 psi without the ac on on both high and low side, once you engage the ac low side should drop to around 35 ish,l and high side should be in the 225-250 ish range temp dependent . Sucks on a boxster that you cannot easily look and see if the compressor clutch is engaging .

Baz · Baz's Garage

Baz · Baz's Garage

Bob Kontak · Bob Kontak's Garage

Quote:

Originally Posted by fastfredracing

Sucks on a boxster that you cannot easily look and see if the compressor clutch is engaging .

You should be able to hear it engage with a click with engine lid open?

I thought if the light was turning on that meant the electrics were ok but I'm not sure if it means the clutch is engaging.

DWBOX2000 · 08-01-2023, 08:11 AM

Thanks everyone. I appreciate you sharing your knowledge.
David

DWBOX2000 · 08-01-2023, 09:13 AM

The rpm’s definitely increase then drop when I hit the ac button.

rfuerst911sc · 08-01-2023, 11:54 AM

How much foam has been coming out of the vents ? If most/all the foam on your blend doors is gone you won't get squat of heat or AC . This is a known problem for 986/996/987/997 .

You can pull the service panel on the firewall . You can then watch/listen for the AC clutch to engage . In the front trunk on the passenger side next to the battery are removable plastic covers . When removed you are now looking at the low and high pressure valves .

If the AC is working at all you will feel a temp difference on the aluminum pipes .

Superman · 08-01-2023, 12:36 PM

Some auto parts stores will loan you the gauge set and vacuum pump for free. AutoZone does this in our area.

Lots of videos on this. Watching them will tell you what to do.

But first, checking the fuse is a good idea and visually checking (or listening for) the compressor clutch to engage, are all good ideas. If the clutch is working, then you should have at least cool AC air if not cold air. If not, then your refrigerant has likely leaked out. If you suspect this, then use a 'black light' to see if you can find the leak. This will work IF the refrigerant had the special dye in it. Most common leak places are at the Schrader valves, at the o-ring connections of the hose/tube system, or at the nose seal on the compressor. The leak can be at the compressor nose seal, but more often is at an o-ring or Schrader valve.

If you put refrigerant in, then use the stuff with the special dye. For most of us, putting refrigerant in probably means releasing what is in there first, then fill it with the specified weight of refrigerant for your system. Using a kitchen scale. The oil that is in the system will likely stay there so you don't have to guess at that, but this requires that the system be released very slowly.

Lots of videos on this.