huesmann

A/C is blowing ambient temp. Compressor clutch engages, but no cooling. Hooked up a HF manifold gauge set to check pressures—looped charge hose, opened connector valves, opened manifold valves. Low side showed zero and the high side something like 100. Closed valves. Hooked up a can of R134a to charge, opened the connector valves and the low side manifold valve, but it doesn't seem to have taken any refrigerant from the can. The can never really got cold the way it should, or lost any weight.

Troubleshooting from here?

pjensen

Hook up the gauges with the ***** closed (with a/c turned off). You should see the same pressure on both the low and high pressure sides. If not, something is wrong with the gauges or the hose connectors.

huesmann

Gauge set worked to charge another car right after pulling it off the Vette.

¯\_(ツ)_/¯

pjensen

The reading of zero on the low side is not possible if there is 100 psi on the high side.

Maybe something is wrong with the low side connection.

huesmann

Maybe, but why would it work correctly on the other car?

pjensen

Maybe the schrader valve on the the low side (on the corvette) is damaged. So the low side gauge will show zero. And no refrigerant can be added.
I would get a schrader tool and twist it just a little bit - wear gloves and face protection as it will blow out some gas. If so, get a tool that can remove the schrader valve and replace it with another (and not lose the refrigerant).

redzg

Sounds awfully sensible!

huesmann

Got the valve replacement tool and new valves on the way; will update later.

Bill Curlee

When you connect the hose to the LOW SIDE, the small depressor button inside the hose may not be long enough to depress the valve in your low side sharader valve. Sometimes you can adjust the length of the depressor button inside the hose and that will make it open the low side valve so you can see pressure/add R-134.

CHARGE TIP: Always charge the low side with the can in the UP-RIGHT direction. You can put the can in a pail of hot water and it will help the liquid R-134 in the can turn to GAS. It makes the charge go a little quicker.

huesmann

Same manifold gauge set had previously worked before to charge the same Vette. Not sure why it wouldn't work now, unless the valve is damaged somehow.

I do charge upright, and in hot water—it's a PITA keeping the thing submerged when the can gets lighter due to the air pocket in the hollow bottom of the can!

huesmann

Replaced the low side schrader valve with the Mastercool 81490 tool, and tried to charge again. No dice. Confirmed that the manifold is still working (at least to charge) by topping off another car. R134a can got very cold.

New ideas?

pjensen

Just to confirm, you have the r134a can connected to the center hose of the gauge set. And the high pressure gauge **** is completely closed (full clockwise). And the low pressure hose is connected to the lows side (with that gauge **** off).

If you just slightly twist open the hose on the low pressure side (of the gauge set), you should get a gentle hiss of escaping gas. Wear latex gloves and eye protection... Close it and try the same on the high pressure hose.

Remove the gauge hose from the low pressure side and press the schrader valve pin down with a screw driver (ever so slightly). You should get a blast of gas.

If not, something is seriously wrong with that valve and/or the tubing. You might need to have an a/c service place recover the r134a, then take that tube out and look at it. Use a flush gun to blast it clean inside.

huesmann

Yup, same settings on Vette that work to charge the other cars: both fittings open, low pressure valve on manifold open, high pressure valve on manifold closed, can connected to yellow hose.

FWIW, there did seem to be pressure in the (hard) line. When I swapped the schrader valve, the plunger rod on the Mastercool tool did get pushed up by the line pressure, and when I removed it from the fitting there was a little "pop" from the residual pressure in the connection.

huesmann

If the pulley clutch is engaging as it should, is it possible for the compressor to be bad or not working correctly?

pjensen

When the clutch engages, does the high side gauge rise? If so, what is the PSI?

huesmann

I don't know if the high side changes because the high side valve is kept closed when charging. Or do you mean in diagnostic mode when both valves are open?

pjensen

The high side gauge is connected to the high side hose. The **** should be closed. It will still read the high side pressure.

There are a lot of youtube videos on a/c gauges. Watch a few....

huesmann

Well, after finally getting my HF gauge set on it as the instructions say (valves on manifold closed, valves on fittings open) the low side reads zero, and the high side reads about 115 psi. What's what mean?

redzg

huesmann

To be clear: I was getting zero low and 115 high with the engine running and A/C "on" full.

What's "black death" (aside from bubonic plague)?