Better Beaters - Building Cars and Daily Drivers

Thinking about automotive a/c Part Two.

This photo was taken during the Navigator re-test.

I had the a/c in my truck flushed and recharged, but I wasn't satisfied that there was a substantial improvement.

I felt that the a/c wasn't cooling enough, before the recharge, but I didn't have a base line measurement to compare it with after the service.

My complaint was that the a/c wasn't cooling enough when the temps were above 90 degrees, or higher. It should have still cooled the air, but my truck is 17 years old. It's never had the a/c serviced since the compressor seized up right after it was out of warranty! The entire system was replaced, and was working satisfactorily until just recently. 

So I googled, how cold should my car's a/c get? There was some conflicting info. One site said that the a/c has to be 20 degrees cooler than outside air to be effective. Another site came right out and said that the temp of a properly functioning a/c should be between 35 and 45 degrees. That is pretty cold.

I watched several videos on the web about how to measure a/c performance. It was pretty easy, use a probe type thermometer, stick it in the vents, and measure the temp. Even if it isn't super accurate, it will give me a reference point.

On the afternoon that I performed my tests the ambient temperature was 85 degrees. 

So I tested the a/c in my truck first. I closed all the dash vents and stuck the probe in the center vent.  The results varied: 48.6, 46.4, 45.0, 42.4. This was after I had cleaned the condenser. 

Then I tested the Flex, I assumed that my newest car should be pretty good at cooling the air. I haven't had any complaints about the a/c. The results were 41.2 and 40.6. That didn't seem to be much better than my truck.

I knew that the Navigator couldn't handle temps over 90 degrees. I had taken it to the Santa Rosa area on a weekend getaway where temps were 105 degrees. It just didn't get cool enough. On the drive home as I approached the Bay Area, temps were in the low 80s and the a/c felt much more effective.

I decided to test the Navigator just as it was.

results of the first test.

The results were 63.5, 60.1, 59.5. 60.8 and 62.1

Bugs.

Yeah, the condensor was a bit dirty.

There were some bugs and dirt on the surface.

The shop vac with brush attachment will clean the surface
without damaging the coils.

First, I used a brush attachment on my little shop vac to remove a small deposit of leaves and a few smashed bugs

After that, I blew through the core with compressed air.

Having a big shop compressor comes in handy.

Then I sprayed a diluted mixture of Castrol Super Cleaner on the core, and let it sit for ten minutes.

I used a spray nozzle on the garden hose to flush the coils, and followed that with more compressed air to blow that water out and dry off the engine a bit. I wasn't going to replay my mistake that I had made with my truck! 

The condensor looks a bit better.

I started the engine and let it run to dry off the radiator and engine area. 

Then I retested the a/c to see if there was any improvement, and there was! Look at the gauge, up to a 10 degree lower reading!

Any improvement is welcome.

The radiator area of the '06 Mustang is not as accessible as my other vehicles. My visual inspection didn't reveal any junk blocking the condenser. I first used compressed air to blow through the core. Then I used the cleaner and rinsed the condensor off. Moe compressed air dried the area. The initial test results were pretty good; 38.8, 39.9, 37.2. 40.6, 41.0, and 39.4. This was the best performance of all my cars!

You might be wondering why the temps vary. It's not like the a/c compressor runs continually. On most modern cars the a/c compressor cycles off and on. On many cars, the a/c compressor will cut out when the engine is idling, or if the engine temp gets too hot, or the engine is racing during acceleration. Also, remember that my procedure was kind of crude, but at least I used a digital thermometer! 

The performance should be better when the car is in motion and air flow is increased. 

The takeaway from my experience is that the best thing is to periodically clean the condenser and radiator. It can help a marginal performing system work well enough to get through the Summer. 

When the a/c in your car is not working as well as it used to, you shouldn't ignore the problem. Systems will lose some refrigerant over time, and over the years it makes quite a difference. If there is a substantial drop in system pressure, a switch will cut out the compressor clutch, so that the system is protected. The refrigerant not only provides the cooling, it also lubricates the compressor, So if the system completely fails to work, there might be a leak. My '96 Mustang had a leaking a/c hose early in my ownership. They were both replaced and the system was charged back up. It's still working after ten years, but I haven't had the chance to test it yet.

Working a/c in a car is a big deal, it adds so much to the comfort of the driver. It makes an old car really useful for the owner.

My Riviera HVAC system isn't working at all. Part of the problem is that the digital control panel doesn't appear to be working. I can't read the numbers or control settings. The fan doesn't work in the vent or defroster settings. I plan to change out the blower control resistor module and look for a rebuilt control panel. I've already replaced both of those components with used items from a wrecking yard, without success. I also pulled the blower out and found that it worked fine. 

The shop that I used for my truck might be a good place to get work done, but I'm still a bit leery. I might retest my truck and then return to ask what else could be wrong. The blower and vents work correctly.  

Further investigation will be needed, before I let the shop work on my Navigator.