[mrblanche]

The A/C on the El Camino has been working fine. Oh, it cycles more than I think is normal, but it would get you good and cold.

On the way to the animal shelter this morning (where I volunteer on Mondays), I heard a funny sound like an impolite 3rd grader. Pppppppppht. Then the A/C quit cooling.

Here's the funny part. The compressor is continuing to cycle. The refrigerant is flowing. I checked on the pressures, and it seems to be OK. But!!!! The bottom line on the evaporator, which is the high-pressure line, is now cold after the connection right by the receiver/dryer. It's hot to that point. And the upper hose and receiver/dryer are now warm, instead of cold and sweaty.

Any clues?

 

[Bobby78]

Clogged orifice tube maybe?

 

[acauth1]

Sounds like the noise you heard was refrigerant releasing, and the suction line being warm is an indication of low charge. What are your pressures?

 

[HP11]

I checked on the pressures, and it seems to be OK.

Are you reading both the high an low side or just the low?

 

[mrblanche]

Sounds like the. The noise you heard was refrigerant releasing, and the suction line being warm is an indication of low charge. What are your pressures?

It's not low. 200 and 25, high and low side.

 

[HP11]

25 on the low side is low and 200 on the high side could be high depending on what refrigerant you're running.

 

[acauth1]

25 on the low side is low and 200 on the high side could be high depending on what refrigerant you're running.

Correct, 25 is too low, regardless R12 or 134a. 200 on the high side is probably too high either refrigerant, especially if the system is low on charge. I suspect you probably have a high side issue hence the pressure noise and probable refrigerant lose. Check your fan clutch, shroud and cooling system.

 

[mrblanche]

Those pressures are the same as when it was working just fine. Whatever happened is not related to sufficient refrigerant. A clog or failure in the expansion valve sound like a more plausible cause.

 

[lsrx101]

Those pressures are the same as when it was working just fine. Whatever happened is not related to sufficient refrigerant. A clog or failure in the expansion valve sound like a more plausible cause.

No sir. acauth1 is absolutely correct.
What you describe are classic symptoms of a condenser airflow issue. Unless you took your earlier pressures at the same ambient temp, underhood temp and humidity as your present readings, comparing the two useless.

Spray water on your condenser and watch the high side gauge. If you have an airflow issue, the pressure will drop like a rock. (I suspect it will)
When your system vented due to the excessive pressure caused by poor airflow, you lost refrigerant. You are now low on refrigerant and the hotter condenser is keeping the High side pressure "artificially" high.

 

[acauth1]

You asked for A/C expert advise. It was given by a professional with over 35 years in the auto a/c business, who is also an ASE master tech, 25 psi low side is too low and an indication of a low charge. Suction line at evaporator outlet and accumulator being warm are also an indication of low refrigerant charge.

You do not have an expansion valve on your 86. You have an orifice tube installed in the inlet to the evaporator.

The bottom line on the evaporator, which is the high-pressure line, is now cold after the connection right by the receiver/dryer

This means the orifice is doing its job, as refrigerant enters the orifice tube and exits to the evaporator inlet it changes state from a high pressure liquid (hot) to a low pressure vapor (cold.)

I heard a funny sound like an impolite 3rd grader. Pppppppppht. Then the A/C quit cooling.

Again, an indication of refrigerant release.

A restriction in the low side of the system would be showing a much lower pressure reading and probably rapid cycle. A restriction in the high side system between the compressor and high side service port would probably not show as high a reading as 200psi, and probably blow your pressure release valve in short order. A restriction in the high side between the service port and orifice tube, (a few inches) would probably be much higher than 200psi.

The fact that it is not cooling, has pressures of 200psi over 25psi again is low low side, slightly high high side. Look for cooling system problems, fan clutch etc.

 

[acauth1]

No sir. acauth1 is absolutely correct.
What you describe are classic symptoms of a condenser airflow issue. Unless you took your earlier pressures at the same ambient temp, underhood temp and humidity as your present readings, comparing the two useless.

Spray water on your condenser and watch the high side gauge. If you have an airflow issue, the pressure will drop like a rock. (I suspect it will)
When your system vented due to the excessive pressure caused by poor airflow, you lost refrigerant. You are now low on refrigerant and the hotter condenser is keeping the High side pressure "artificially" high.

You beat me too it, I was typing, thanks!

 

[mrblanche]

OK, I know I have a condenser problem...because it got hit some time in the past. I have a replacement to put on it, and it looks like that may be in the cards now.

But the puzzler is it was working just fine. It went from that to making a funny noise to not producing much cold in the space of 30 seconds or so. And the inlet line into the evaporator is very cold after the junction right by the dryer. It's hot to that point. Is that where the orifice is? I can get out my infrared thermoment and give you temp readings on those lines, it that would help.

 

[mrblanche]

No sir. acauth1 is absolutely correct.
What you describe are classic symptoms of a condenser airflow issue. Unless you took your earlier pressures at the same ambient temp, underhood temp and humidity as your present readings, comparing the two useless.

Both pressure readings were in my garage, similar outdoor temperature and humidity.

What are you meaning by "an airflow problem?"

I just went out and put some refrigerant in it and checked the pressures. Over 250 on the high side, about 30 on the low side. Backed it out and hit the condenser with water. As you predicted, about 100 on the high side, same 30 pounds on the low side.

Enlighten me!

 

[acauth1]

Enlighten me!

We did. Fan clutch, fan shroud, cooling system. Check them.

 

[mrblanche]

Fan clutch is fine. Fan shroud is fine. Cooling system is now fine, since I found the leak.

Where is that pressure relief valve. On the compressor? Is there any way I can tell if it released some pressure? That would sure fit the sequence of events.

 

[Bobby78]

It should be on the back of the compressor. Check for any oily stains.

 

[mrblanche]

Thanks, you guys have been really helpful.

So, it looks like my next project, rather than being the new intake manifold, will be the A/C system overhaul. I have a replacement condenser. While I'm at it, should I replace the orifice tube? If so, does anyone have the correct part #? I found several, with prices from $2 to $72. And how about the accumulator?

 

[acauth1]

How are you testing the fan clutch? Until you solve your air flow issue I wouldn't recommend changing parts just yet.

 

[mrblanche]

The fan has the normal resistance to turning before starting. It turns pretty close to engine speed after starting. But I can't say I've ever heard the loud roar of it locking up. Maybe I'll just include one in my parts list.

On another note, if I found the pressure relief valve on the compressor, it's not showing any signs of having released refrigerant.

 

[acauth1]

It should spin relativity free until warm up, and then gain resistance. Once warm, it should stop when you shut the engine down, if it continues to spin, it's trash. If you search Bobby's posts you'll find the method I posted for properly diagnosing the clutch.

Sometimes the relief valve will not show any trace of leakage, not enough to just eyeball it.

From your pressure readings the system is low.