Looking for some guidance on this topic. I live in Northern Ohio and I’m in the market for a nice chrome bumper with a lot of options including A/C. I have a feeling my search will last at least a couple months, so as the weather begins to cool down what’s the best way to confirm that the a/c is, in fact, working in a c3? Statistically most systems don’t work, so this is a concern I have when purchasing a car with the temperature below 70 degrees. Any thoughts?
Andy

 

As you’ve already noted, there is a very good chance on the ac not working.

Also a good chance that some components may not allow for the system to work at max efficiency, yet appear functional.

I would say, check to see that the compressor is turning on would be the #1 test to look at.

#2 would be to see if the fan speed switch works on high, as well as the three lower settings.

Outside of that I’m going to say bring an infrared temp gun and point it in the vents, comparing the temp of the vents just on vs with ac on.

This is just a starting point, and hopefully others better at the cool air game will chime in with more to add.

 

Trying to check A/C operation at lower ambient temps is doable, but......

Here are a few suggestions, some apply to orifice tube systems and others to expansion valve systems.

​​​​​​As mentioned above, check and make sure the compressor clutch is engaging, blower speeds work, and mode doors are functional.
If the temps are around 70+ , run the system, and check the air out the closest vent on low fan speed. You should see a 30* drop in temp from ambient temp.
If it is colder outside, you have to make the system work by restricting airflow through the condenser.
I usually use a plastic floor mat and cover half of the condenser. This makes the system think it is hot outside.
Your freeze switch or high pressure compressor cut out switch will probably limit the amount of time the compressor runs, due to elevated high side pressure( because the condenser is blocked) or, the evaporator core is getting too cold.
If it has a thermoststic fan clutch, it should lock up and provide full draw through the radiator. What temp will that happen, you ask ? I don't know, but I would expect it to be around 200* or less. The systems I've worked on are mostly equipped with pressure controlled fan switches that turn on the fan at about 325 psi. Some have the thermal clutch, but not many.
Feel the suction and pressure lines.
On an orifice tube system:
From the compressor to the condenser, it will be hot, from the condenser to the evaporator, it will be warm/ hot to the touch, but much cooler than the line to the condenser. The suction line will be cold from evap core, to the accumulator, and back to the compressor.
On an expansion valve system:
The line from the compressor to the condenser will be hot, from condenser to receiver/ dryer it will be warm/hot, and from the dryer to the expansion valve, it will be warm/hot. From expansion valve back to compressor, it will be cold.
Any A/C system that is functioning even close to normal, will have an almost uncomfortably cold suction line.

Trying to check A/C fuction in low ambient temps is definitely a PITA.
​​​​​ Keep in mind, the system operates whenever the defrost mode is on, even in winter.

General guide, but it may help, then again, maybe not.

Good luck.
Jeff

 

Dave/Jeff,
Outstanding information here. This will prove to be very helpful to me and other forum members. Since it'll be a C3 I'm sure I'll have to use this info at some point even if the a/c is working when I get it.
Thanks again.
Andy