Hot air comes from A/C, how to locate the the faulty parts?

[Tony_1992]

Hi everyone, I have a Lincoln LS 2004 V8 mode, and now only hot air comes from all. I hope you could help me locate the problematic parts and to fix it.

The A/C is not cooling since I bought this car last year even if I set it to 60 degree. I thought it was because of the lack of refrigerant, so I bought some r134a and charged the compressor. But things are not getting better. The A/C even blows air hotter than ambient temperature.

I've done some search and some posts told me that it was probably due to DCCV. But since there are too many parts in the A/C system(compressor, hoses, tubes and of course DCCV), how can I make sure it IS the problem of DCCV? Is there some ways to exclude the probability of other parts being faulty?

If I can make sure that the compressor, the evaporator(maybe this name) are working well, I can replace the DCCV.

Thank you guys!

 

[1LoudLS]

crash course in the LS.

first if you didn't use a set of gauges (correctly) and actually verify that you were indeed low and needed refrigerant, then you likely have other problems now...

second, if the air is actually hot then it is very likely that it is the DCCV, and there have been a thousand threads on such and most of them even tell you how to test for it.

 

[Tony_1992]

crash course in the LS.

first if you didn't use a set of gauges (correctly) and actually verify that you were indeed low and needed refrigerant, then you likely have other problems now...

second, if the air is actually hot then it is very likely that it is the DCCV, and there have been a thousand threads on such and most of them even tell you how to test for it.

First, thank you for your reply. Actually I did use a built-in gauge of Pro A/C, and the pressure should be right about 35psi. So I think the refrigerant is not insufficient any more.

By the way, how to check if the compressor is working well, like checking the temperature of some parts? I can see the belt is turning.

 

[1LoudLS]

First, thank you for your reply. Actually I did use a built-in gauge of Pro A/C, and the pressure should be right about 35psi.

so by yes, then you actually mean no. the built in gauge does not tell you the high side, only the low side that it is connected to. you can't diagnose an AC problem without the right equipment.


but, if you have hot air coming out of the vents as stated (as apposed to near ambient temps), you don't have an AC problem (well you might now, but that's a separate problem). the AC system cools air, the DCCV is what heats air. so if you have hot air, its going to be the DCCV, the controller, or the wiring between the two. have you tried a sefl test?

 

[Tony_1992]

so by yes, then you actually mean no. the built in gauge does not tell you the high side, only the low side that it is connected to. you can't diagnose an AC problem without the right equipment.


but, if you have hot air coming out of the vents as stated (as apposed to near ambient temps), you don't have an AC problem (well you might now, but that's a separate problem). the AC system cools air, the DCCV is what heats air. so if you have hot air, its going to be the DCCV, the controller, or the wiring between the two. have you tried a sefl test?

I just made a test. The ambient temperature is 58 degree. The air is pretty hot if I set the temperature to 90 degree, that is heating.

And then I set the temperature to 60 degree, the air coming out is not as hot as in the day time, but still definitely hotter than the ambient temperature. Is that the symptom of DCCV failure?

And are you talking about self test? I pressed the defrost and off button followed by auto button. The code is 1265, meaning Cold air bypass door actuator circuit failure? Not quite sure if it's the problem.

Thank you.

 

[Tony_1992]

so by yes, then you actually mean no. the built in gauge does not tell you the high side, only the low side that it is connected to. you can't diagnose an AC problem without the right equipment.


but, if you have hot air coming out of the vents as stated (as apposed to near ambient temps), you don't have an AC problem (well you might now, but that's a separate problem). the AC system cools air, the DCCV is what heats air. so if you have hot air, its going to be the DCCV, the controller, or the wiring between the two. have you tried a sefl test?

And also I noticed a weird sound like si~~~~~~ when I tried to cool down.

 

[joegr]

Okay, this has been covered a thousand times...

You can't correctly charge the AC refrigerant without a high side gauge and a low side gauge. With those, you have to correctly set the conditions (blower on max, windows open, RPM at spec for the chart, wait several minutes to stabilize). Then you have to compare the pressures with the chart for the air temperature that you have. Too much refrigerant is even worse than not enough.

That hissing sound that you hear is from the thermal expansion valve. It means that the system is incorrectly charged or the valve or compressor has a fault.

Ignore 1265 because your LS doesn't have a bypass door. It's a software bug that the finally corrected in 06.

Wait till your engine is completely cooled down. Start it and turn the AC on. Do you get cold air out at first? Does it stop being cold as the engine starts to warm up? If so, then you have a bad DCCV or bad wiring to it. Since you don't have any DCCV codes, then the wiring is good and it must be a mechanical failure of the DCCV.

If you don't get cold air at cold engine startup, then you have a refrigerant system problem. You need to study up on how the refrigerant system works and get the correct tools if you want to fix it, otherwise take it to a dealer or an AC shop.

 

[Tony_1992]

Okay, this has been covered a thousand times...

You can't correctly charge the AC refrigerant without a high side gauge and a low side gauge. With those, you have to correctly set the conditions (blower on max, windows open, RPM at spec for the chart, wait several minutes to stabilize). Then you have to compare the pressures with the chart for the air temperature that you have. Too much refrigerant is even worse than not enough.

That hissing sound that you hear is from the thermal expansion valve. It means that the system is incorrectly charged or the valve or compressor has a fault.

Ignore 1265 because your LS doesn't have a bypass door. It's a software bug that the finally corrected in 06.

Wait till your engine is completely cooled down. Start it and turn the AC on. Do you get cold air out at first? Does it stop being cold as the engine starts to warm up? If so, then you have a bad DCCV or bad wiring to it. Since you don't have any DCCV codes, then the wiring is good and it must be a mechanical failure of the DCCV.

If you don't get cold air at cold engine startup, then you have a refrigerant system problem. You need to study up on how the refrigerant system works and get the correct tools if you want to fix it, otherwise take it to a dealer or an AC shop.

Hello Joeger. Thank you so much for helping me figure out.

Today I made another experiment under ambient temp about 75 degree. When I start the engine at cold status, turn on A/C, I don't think that any cool air comes out. I mean, if it's the DCCV problem, at least I should feel come cool air at first.

I'm thinking of buying this gauge and vacuum set to test the pressure in both low and high port of compressor to see if it's working well. Could you give me their reference pressures? Like what should the low and high pressure should be, supposed that the compressor is working well.
Amazon.com: Zeny Combo 3,5CFM 1/4HP Air Vacuum Pump HVAC A/C Refrigeration Kit AC Manifold Gauge Set: Automotive

By the way, I'm still not quite clear how the DCCV works. Do you have any system diagram ofair conditioner?

Thank you!

 

[joegr]

I am a little skeptical of that vacuum pump...
Charts here: 2006 Lincoln LS Workshop Manual

The DCCV is two solenoid valves that control the amount of coolant flowing in each of the two heater cores. (The driver's side core is bigger then the passenger side core.) With no power applied to the solenoids, the valves are fully open (full heat). With 12V applied to the solenoids, the valves are fully closed (no heating or full cooling). The solenoids are PMW'd to get levels between full heating and full cooling. The AC compressor runs all the time. Heat is added as needed to get the desired cabin temperature.

The compressor is a variable displacement scroll. There is a thermal expansion valve on the evaporator. The result is that the warmer the evaporator is, the harder the AC system works. If the evaporator gets near freezing, the compressor it turned off till it warms back up some.

 

[Tony_1992]

I am a little skeptical of that vacuum pump...
Charts here: 2006 Lincoln LS Workshop Manual

The DCCV is two solenoid valves that control the amount of coolant flowing in each of the two heater cores. (The driver's side core is bigger then the passenger side core.) With no power applied to the solenoids, the valves are fully open (full heat). With 12V applied to the solenoids, the valves are fully closed (no heating or full cooling). The solenoids are PMW'd to get levels between full heating and full cooling. The AC compressor runs all the time. Heat is added as needed to get the desired cabin temperature.

The compressor is a variable displacement scroll. There is a thermal expansion valve on the evaporator. The result is that the warmer the evaporator is, the harder the AC system works. If the evaporator gets near freezing, the compressor it turned off till it warms back up some.

OK, please correct me if my understand is wrong:

When I turn on the A/C, the compressor is actually working all the time. And the job of DCCV is to exchange and allocate heat between hot coolant and two heater core(right)? For some people feeling different temperature in driver and passenger's side, they might have a problem in DCCV, cause one of the solenoids is not working normally.

But for my case, I cannot feeling any cool air comes from the vent at all, even at the first several minutes when engine starts from cold. And also I can hear the hissing from the vent when A/C is on max cooling. So what I'm facing now is probably the compressor or thermal expansion valve problem?

I mean, if I tested the low and high pressure of compressor and they are within the normal range, does that mean the compressor is working well?

Thank you.

 

[1LoudLS]

if at first start up, the air doesn't get cold, then the air conditioning system* is not working, but/and if the not cooled air starts to get warmer as the engine temp does, then their is a DCCV problem.

keep in mind that due to the HVAC system, you may be having multiple problems at the same time. both may need to be addressed.


*we can guess at it all day, but to know whats actually wrong, testing needs to be done.

 

[joegr]

If the pressures were both correct, then the system would be cooling. If the pressures are wrong (they must be, it isn't cooling), then it could be the compressor or the expansion valve. Figuring out which it is can be tricky, depending on what readings you are getting.

Sometimes, the control valve on the compressor fails. (This part can be replaced without replacing the compressor.) Usually when this happens, you get no cooling at idle, but some cooling at higher RPMs.

Sometimes, the seal on the control valve leaks slightly, and most of the compressor oil leaks out before the refrigerant does. When this happens unnoticed, the compressor internals come apart and ruin the whole system. You can flush the lines, and if you have the right machine, you can flush the evaporator. (The problem is not the flushing, it's getting all the flush chemicals back out.) Still, the compressor, condenser, dryer, and expansion valve would have to be replaced.

Are you sure your compressor is running?

Sometimes the AC clutch fails. Sometimes this can be fixed by adjusting the air-gap. Other times it's a new clutch or new compressor with clutch.

Sometimes the evaporator temperature sensor fails and this causes the climate control to keep the AC compressor off.

If the system pressure is too low or too high, the climate control (DATC) won't turn the compressor on.

 

[Tony_1992]

If the pressures were both correct, then the system would be cooling. If the pressures are wrong (they must be, it isn't cooling), then it could be the compressor or the expansion valve. Figuring out which it is can be tricky, depending on what readings you are getting.

Sometimes, the control valve on the compressor fails. (This part can be replaced without replacing the compressor.) Usually when this happens, you get no cooling at idle, but some cooling at higher RPMs.

Sometimes, the seal on the control valve leaks slightly, and most of the compressor oil leaks out before the refrigerant does. When this happens unnoticed, the compressor internals come apart and ruin the whole system. You can flush the lines, and if you have the right machine, you can flush the evaporator. (The problem is not the flushing, it's getting all the flush chemicals back out.) Still, the compressor, condenser, dryer, and expansion valve would have to be replaced.

Are you sure your compressor is running?

Sometimes the AC clutch fails. Sometimes this can be fixed by adjusting the air-gap. Other times it's a new clutch or new compressor with clutch.

Sometimes the evaporator temperature sensor fails and this causes the climate control to keep the AC compressor off.

If the system pressure is too low or too high, the climate control (DATC) won't turn the compressor on.

That's really helpful. I can see the belt connecting the compressor is rolling so I think the compressor is at least being driven.

I've made a plan to test the A/C system. I bought a manifold set and vacuum from Amazon. First I'm gonna read the low and high side pressure while the engine is on and A/C to its max cooling. If pressures lie in normal interval, then the compressor is surely working. Otherwise, I'm gonna fully check the compressor.

And you said the temperature sensor failure also might be the culprit. How to do test on it? I want to exclude that possibility first.

Another news today, Tireplus is gonna charge me for 150 bucks for a pound of R134a, as stated, $150. I can but a whole set of A/C tools.

 

[joegr]

That's really helpful. I can see the belt connecting the compressor is rolling so I think the compressor is at least being driven...

The AC compressor pulley will always turn with the engine. It's the inner part that you need to look at, to see if the clutch is engaging or not.
Start up the engine and turn the climate control off. After a few seconds, turn it on. Do you hear a click from under the hood and does engine speed change ever so slightly? Does the engine fan speed up? Get someone to look at the AC pulley while doing this. It is easier to see from below than above.
If the fan doesn't speed up, then the high-side pressure is low.

There is no need to check the evaporator temperature sensor if the AC clutch is engaged. If it's not, then you can eliminate the sensor by unplugging its electrical connector. It's under the dash on the driver's side, but towards the center. It's about halfway up the ductwork, and the sensor is white(ish). If it cools when you unplug it, then you need a new one.

There's more to AC work than a simple set of tools. They were probably going to properly weight it in and make sure you have the correct amount.
If you DIY, then you'll also have to add the correct amount of the correct oil. This is tricky, because some oil remains in the parts of the system, so you have to estimate the correct amount. You'll also need to replace the receiver/dryer. That's a cheap vacuum pump, and those gauges don't go down to microns (for vacuum), so you have no way to know when you have vacuum boiled all the moisture out. You'll just have to leave the vacuum pump going for an hour or two.
I'm not trying to say you can't do this. I am trying to say that you need a lot more than this forum to go on to learn how to do it correctly.

 

[RigsLS]

Be sure he understands the part if he keeps running the AC with no refrigerant in the system, which provides the needed lubrication, he'll need a new expensive compressor.

BTW Joe, I still haven't gotten around to replacing that seal in my 04, still blows cool air and defrost works, using it as little as I can for the time being. Not leaking any further. Will get to it eventually.

 

[Tony_1992]

Be sure he understands the part if he keeps running the AC with no refrigerant in the system, which provides the needed lubrication, he'll need a new expensive compressor.

BTW Joe, I still haven't gotten around to replacing that seal in my 04, still blows cool air and defrost works, using it as little as I can for the time being. Not leaking any further. Will get to it eventually.

Thank you. I'll keep in mind that never let the A/C run without refrigerant inside.

 

[RigsLS]

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