Air conditioner question...

[AKmud]

So my 16yo daughter bought her first car this past summer, a 2002 Ford Taurus SEL. It's in very good condition, but the previous owner removed the air conditioner compressor after it went bad on him. I never found out what he meant by "went bad" so I don't know if it fragged internally or what. He just said it was around $1k to fix it and he didn't want to spend the money so he just removed the compressor.

All was fine and dandy this summer...get hot, open the windows, etc... Now that Jack Frost has taken over again and we have sub-zero temps, she is having a hard time defrosting the windows. Now I'm thinking I may end up having to fix the A/C system after all.

My question is... What do I need to look at when bringing this system back online? I've heard I may end up having to replace nearly all the components since the system has been open. At the very least it all needs to be flushed I guess. I found a used compressor at a salvage yard for $120 which would make it reasonable fix if I could get it done for under $300 or so with a re-charge.

Also, is there something different with the way air is routed for a car with A/C vs. without? I've had vehicles before with no A/C and never had a defrosting problem. I know A/C dries the air which would make defrosting more efficient, but with good airflow it seems it should be clearing up better than it is.

[Snuffy]

A/C and the defrost have nothing to do with each other. The engine coolant is routed through the heater core which is a small radiator under the dash. Mount a fan on it and ya got heat. The A/C compressor compresses the gas then when it decompresses it gets really cold. Insert fan and ya got A/C.

[weldermike]

I just text my friend bud. Waiting for a answer.Great mechanic and builds and guts a lot of race cars. he should know.

[BD1]

I can't help sorry, but here's a site if you haven't been there that could. http://www.garagejournal.com/

[AKmud]

A/C and the defrost have nothing to do with each other. The engine coolant is routed through the heater core which is a small radiator under the dash. Mount a fan on it and ya got heat. The A/C compressor compresses the gas then when it decompresses it gets really cold. Insert fan and ya got A/C.

So why does the A/C compressor kick on with the defrost on my other vehicles? I thought they were tied together to help dry out the cabin air.

[AKmud]

I can't help sorry, but here's a site if you haven't been there that could. http://www.garagejournal.com/

Forgot about that one, thanks for the reminder BD1.

[weldermike]

Just got a reply from my friend. He said it shouldn't matter and you probably have a vacuum line off.

[AKmud]

Thanks Mike, I'll delve further into it then.

[Snuffy]

Drying is a side effect from the moisture condesating from the cold. The only thing the compressor does is make cold. The heater core works off engine temp. That's why you have to wait for the car to heat uo to get heat where you get cold immediately after the compressor kicks on. Are you watching the compressor clutch to tell if it's kicking on or not with those other cars?

[AKmud]

Drying is a side effect from the moisture condesating from the cold. The only thing the compressor does is make cold. The heater core works off engine temp. That's why you have to wait for the car to heat uo to get heat where you get cold immediately after the compressor kicks on. Are you watching the compressor clutch to tell if it's kicking on or not with those other cars?

Yes, as soon as you turn the defrost on the compressor clutch kicks in and starts spinning.

[Bistineau]

So why does the A/C compressor kick on with the defrost on my other vehicles? I thought they were tied together to help dry out the cabin air.

The AC compressor kicks on to remove moisture from the air, then the ACed air is directed over the heater core to warm it before it is blown against the windsheild to defrost it. If you have ever noticed the wet spot behind the right front tire after running the AC, this is the humidity it has removed from the cabin air, just like your home AC has a condensate drain.
Running the AC compressor has the added benefit of keeping the refridgerant circulated thru the system during colder weather to keep the seals lubricated and the system running properly when it would not ordinarily be used(cold weather).
If the car has been smoked in, there may also be a film of smoke on the glass that appears more as a frost when the glass is cold. Give the interior of the glass a good cleaning and see if it doesn't help some with this. I smoke in my trucks and have noticed this to be the case.

[Snuffy]

Hmm. I'll have to screw around with my car tomorrow now. Now I know that compressing gas generates heat. House A/C systems will run the gas through heat exchanger to get rid of the excess heat. This is why your A/C unit blows hot air out when it's running. Then it decompresses and gets really cold. Cars systems have at least in the past been much simpler. As you have an adequate heat source with the engine coolant all the extra stuff is just added weight. If it does kick on simply to dry the air it's news to me.

[Bistineau]

Drying is a side effect from the moisture condesating from the cold. The only thing the compressor does is make cold.

And when it makes cold, it is condensing the humidity from the air to dry it before the heater core warms it to clear the glass faster. Dry air tends to frost up the glass less than highly humid air. The moisture laden air is what causes most of the interior frosting/ice build up.

[Bistineau]

Hmm. I'll have to screw around with my car tomorrow now. Now I know that compressing gas generates heat. House A/C systems will run the gas through heat exchanger to get rid of the excess heat. This is why your A/C unit blows hot air out when it's running. Then it decompresses and gets really cold. Cars systems have at least in the past been much simpler. As you have an adequate heat source with the engine coolant all the extra stuff is just added weight. If it does kick on simply to dry the air it's news to me.

Yes you are correct in that AC systems generate heat when they are working. That is why your outside AC compressor unit is blowing out hot air. This is also the principle of operation of a heat pump system. It is simply an AC system that can be reversed in operation, a backward running AC system blowing heat removed from the outside air and blowing it inside. If you check the outside unit of a heat pump when it is in heating mode, you will find out it is blowing COLD air outside and warm inside. That's why they are inefficient to run at temps below 40* F, as there is not much warmth they can wring out of the air to blow inside below those temps. They have resistance heat strips as a back up for this, and resistance heating electrically is not really energy efficient either.

[RealMcCoy]

As has been stated, most A/C equipped cars pass the incoming air over the A/C evaporator to dry it before sending it over the heater core to warm it up (usually only on the defrost setting)

As far as what it will take to repair, The only thing that MUST be replaced when you put it back together is the receiver/drier. Everything else in the system can usually be cleaned/flushed.

The only exception would be if the condenser is full of metal from a catastrophic compressor failure. If that happens, it often cannot be reliably cleaned and should be replaced.

Once the system is clean, it will need to have the proper amount of the correct viscosity PAG oil added, (generally distributed around in separate components initially to aid in even distribution) then the system needs to be pulled down to a complete vacuum to boil out any moisture and air. Then all that is left is to install the proper amount of R134a refrigerant...

Not really a hard job, but can be time consuming with all the flushing and cleaning, and requires some specialized tooling to do the job correctly...

[Chook]

Just rub the inside of the windows with neat/undiluted dish washing liquid using a sheet of newspaper, or a raw potato cut in halves and they won't fog up.
Try it on your bathroom mirror it really works.

[walker]

Is there air blowing out if the defrost ducts when the dials are adjusted to defrost and the fan on? While the air is drier after going through the cooling coils, then heated After going through the heater coils, you should still have hot air, assuming the engine is hot, blowing on the windshield when the defroster is on. If not then you need to determine if you have a lack of heat, or a lack of air. If no heat you need to find out if you have a bad thermostat , cold engine, or a plugged heater core (cold heater core), or even a bad heater core valve. If you heater core is hot, then you have no, or wrong, air flow. This is generally caused by faulty air duct actuators. These are small gear motors which change the flaps in the ducts to direct the air flow (they haven't used vacuum controls for many years by 2002). Most likely culprit is a bad actuator. If you hear clicking sounds when you change the air duct from ac to heat, or from max to ac, or to heat or defrost, this is the sound of a bad actuator. Next most likely is plugged heater core. You can try and pull the hoses and flush out.

[RaptorDuner]

Is the air intake on "fresh"? My BIL drove their Honda Accord around for 5 yrs with foggy windows because he thought it was supposed to be on the recirculation setting.

[AKmud]

Is the air intake on "fresh"? My BIL drove their Honda Accord around for 5 yrs with foggy windows because he thought it was supposed to be on the recirculation setting.

Good question, I'll have to check. I never drive it myself...

[AKmud]

Just got a reply from my friend. He said it shouldn't matter and you probably have a vacuum line off.

Mike, I did find a loose vacuum connection that I fixed with some new hose clamps. Of course now the weather has been freezing rain and in the 30's. I'll have to wait till the temp drops again to see if it changed anything.

[Dualie]

also it helps to set the defrost on full blown roast beef and use the windows to control actual cabin temp. The A/C dehumidifies the air before heating it.

If your dead set on repairing the AC your going to need a new evaporator dryer and I would recommend flushing the system just incase the reason it died was that the compressor shelled itself and left contamination in the system. Your going to need to replace the compressor and evaporator dryer and pull a vacuum on the system. if it holds a vacuum you can refill with the correct amount of compressor oil and refrigerant

[Rog02]

Mike, I did find a loose vacuum connection that I fixed with some new hose clamps. Of course now the weather has been freezing rain and in the 30's. I'll have to wait till the temp drops again to see if it changed anything.

You should be able to feel the out coming out of the defrost ducts in the dash. The AC not functioning won't keep it from working just that it won't work quite as well and the car will have to warm up a bit more to to clear the windows as effectively.

If you haven't already done so, I would suggest changing the thermostat out. The new ones tend to open at lower temperatures when they get a bit of age on them. I changed the one in my Impala and not only does the heater get hotter, I get better mileage as the ECM was never quite seeing cruise temp for most efficient fuel curve.

[76GMC1500]

AC system flows can be reversed with some simple solenoid valves turning it into a heat pump. That would provide hot air more quickly than waiting for the engine to warm up. Are we sure this is not what is happening?

[brianjk]

All was fine and dandy this summer...get hot, open the windows, etc... Now that Jack Frost has taken over again and we have sub-zero temps, she is having a hard time defrosting the windows. Now I'm thinking I may end up having to fix the A/C system after all.

There may be some confusion here...Defog and defrost are two different things. If the window won't defog then you may need the a/c to dry the air, but if the window wont defrost (as in: melt frozen water) then you probably have a different issue.

If I was dealing with the issue personally, I would get the car up to full hot running temperature, then crank the air to max hot temp and max fan speed through the "defog/defrost" vent. If the air isn't coming out by the windshield and very hot on my hand, then there an issue which needs further investigation.

[RealMcCoy]

There may be some confusion here...Defog and defrost are two different things. If the window won't defog then you may need the a/c to dry the air, but if the window wont defrost (as in: melt frozen water) then you probably have a different issue.

If I was dealing with the issue personally, I would get the car up to full hot running temperature, then crank the air to max hot temp and max fan speed through the "defog/defrost" vent. If the air isn't coming out by the windshield and very hot on my hand, then there an issue which needs further investigation.

I agree... Some clarification of the complaint would be in order. If the issue is that the there just isn't enough heat, I'd be looking to a plugged heater core or airflow control problem. A bad thermostat usually sets a slow warm up code in the PCM and turns on the check engine lamp, so I wouldn't be suspecting that right away.

Plugged heater cores are pretty common in that chassis... The heater does not get full flow and is in parallel with the bypass, so it is susceptible to trapping debris, and getting restricted.