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A Good Four Letter Word

"HVAC"

      Written By Archie Varone from A and J Auto Maintenance Center

 

When I was young

I remember a story my granddad told me about the good old days and cars. In the twenties and thirties a heater for a car was an option that cost a whopping ten bucks. And ten bucks was hard to come by. So many people opted to be resourceful and pack blankets or use mini oil, gasoline and kerosene heaters. He told me of one guy who mounted a cast iron wood stove complete with chimney where the back seat was so they could go hunting in the winter.

When I asked how they kept cool he said they invented auto air conditioning in the forties but no one could afford it until the late fifties. So they made do with the 2-50 method (2 windows down while traveling 50 miles an hour!) He thought that was a HOOT.

Being a teen in the seventies I couldn’t imagine no heat or AC, I thought he was pulling my leg.

Since the seventies we have all taken for granted that our cars will keep us comfortable regardless of weather conditions. Windy winters or sweltering summers at the push of a button and -- Wal-lah !! Instant comfort.

When It’s all GOOD

The HVAC system is one of the most misunderstood systems in a car. Without our heating and air conditioning systems we would not be happy campers getting to where we have to go. We take for granted the heat that keeps us warm in winter and the cold air that keeps us cool in summer.  Understanding how both works is key to keeping them maintained so they won’t let us down.

The heater in your car is basically a small version of your radiator. Hot engine coolant is circulated through a small radiator, (the heater core).  A fan pushes air through the heater core, the moving air pulls the heat from it and goes through the vents and keeps you toasty.

If you keep your car maintained (regular coolant flush and fills) the heater core should last the life of your vehicle. If not, the heater core can become clogged with rust or sludge, giving you poor heat. If it leaks, you might smell a sweet aroma of coolant, or the car may overheat.  In most cases the heater core is under the dash, and if it fails, can be costly to replace. If you feel the heat is not as good as it used to be, a properly done flush and fill may help save it. A word of caution here, if not done properly this procedure could make things worse or fail on the spot.

The air conditioning system is little more complicated but basically has the same function. The system consists of a compressor, condenser, expansion valve and evaporator (see diagram). To make a long story short, the compressor squeezes the freon gas to high pressure, (it gets hot during this process) it’s sent across the condenser to cool it down and it turns into a liquid. The high pressure liquid is forced through the expansion valve (or orifice tube) where it rapidly expands the compressed gas. This process makes the gas turn super cold as it enters the evaporator (looks just like the heater core) the fan pushes air though it and it chills the air you get from the vents. Then the cycle repeats over and over.

 

When things aren’t so cool:

 From time to time the A/C system needs to be recharged to bring it back up to maximum efficiency.  Sometimes a leak may cause loss of refrigerant and will need to be fixed before refilling.  It's difficult to tell if a leak is present without specific test equipment. You or your service tech may be able to inject a florescent dye that may help pinpoint the leak before paying for a full charge.  The EPA has phased out the use of R-12 freon and R-134a has become the new standard.  If you have an older system with R-12 you may need to retrofit your system to handle the new R-134a refrigerant.

  • To convert your system, sometimes seals, hoses and even the compressor need to be changed. (not all systems require extensive conversion)
  •   Ask your service pro if they could locate R-12A  (an alternative to retrofitting the whole system) it cost a little more, but if you’re trying to keep your car original, it’s worth it.
  • Warning! Using DIY kits that contain sealers in them have been known to destroy compressors and ruin the other parts of the AC system. I highly recommend you avoid these products. If you find a leak, have it repaired by a qualified mechanic!

 

When things aren't so hot

Air flow is critical to good heat and air conditioning. Be sure to check the vents that let fresh air into the car, most are under the hood below the windshield. Be sure that they are not blocked by leaves and debris. Also be sure to check your cabin air filter(s) if you have them. If you can’t find them, ask your local parts store or favorite mechanic. If that doesn’t help, you may have poor flow from a clog or corrosion.         

  • Corrosion will cause the heater core to leak or clog up.  A leak may manifest itself by allowing hot vapors into the passenger compartment and make your windshield foggy or slimey. You may know there is a leak by the sweet smell coming from your vents, or maybe wet carpet or a puddle under the center of the car.   Unfortunately changing the heater core is usually not an easy job, as car makers tend to squeeze them into some pretty tight spaces under the dash.

 

When you want it all good

So the next chance you go through the afore mentioned checks and test your heat and AC, if it leaves you hot headed or cold hearted get it checked out. You’ll be glad you did on that next trip with the family or friends. After all, according to my granddad, we’re all spoiled anyway.