HVAC blowing hot even with new A/C parts.

[Crashtifer]

As the title says. I'm sure its been talked about in the past, and I apologize if theres a thread already on this issue, but I've been researching this for a while and have gotten nowhere.

It's been doing this all summer, even when I turn the DATC to its lowest setting I still get hotter than ambient air temps. DCCV has been replaced twice and fuses have been checked. Its not overheating and the radiator fan is working fine. I've also replaced the DATC (with a used unit). And just today I had a compressor, manifold hose and dryer replaced.

Does anyone know of anything other than the usual suspects I can check?

The LS I'm working on is a 2000 model with 156,000 miles.

 

[Buddy A]

Sorry to hear about your headache ..
as I'm in the same boat sorta with my 2006 LS . Replaced the DCCV twice with motor craft the first unit leaking around the upper housing and second unit has a valve sticking on passenger side, both new DCCV defects right out of the box so now I'm going with Four Seasons DCCV hope this one works longer Than a day compared to motor craft ? lol

 

[Crashtifer]

Sorry to hear about your headache ..
as I'm in the same boat sorta with my 2006 LS . Replaced the DCCV twice with motor craft the first unit leaking around the upper housing and second unit has a valve sticking on passenger side, both new DCCV defects right out of the box so now I'm going with Four Seasons DCCV hope this one works longer Than a day compared to motor craft ? lol

Yea those are a pain enough to replace on the v6, I couldn't imagine how it would go on a v8. I've averaged one replacement DCCV at the end of every winter so far, and I'm thinking this one might be toast too. I'm just hoping to find and easier to do solution this time around lol

 

[milehighmikey]

Feel your heater hose lines away from the dccv, check to see if they are both the same temp, to get a start on where to proceed. You may also want to get a total scan done for the car for any clues. There are chassis codes that these cars store on errors, and climate control codes do exist. You could have a fault in your system causing this condition, although setting the plant to 60 probably bypasses any of the items that could cause false readings. For example, my car has a code for right side interior temperature sensor and another code due to a failed recirculate door actuator. Another "C" code is being logged by my cruise control unit, because it reported that the unit fails to maintain speed when set. You'd never know these existed, since they don't light up anything on the dash. I use the Autel Maxidiag Elite code reader tool, pretty cool stuff. It can even kick off built in diagnostics for you for the whole car. I ran one that checked everything, even the side view mirror positioning got checked!

 

[joegr]

You can get the climate control fault code on the DATC display by initiating the self test.

 

[Crashtifer]

The vents on both sides are blowing as hot as the car can put out like the heat is on max. I have also ran the diagnostic mode on the DATC this weekend and a few months back when I noticed the problem, both times reporting a drivers side recirculate blend door issue (B1242). Maybe its a cabin temperature sensor?

 

[joegr]

... both times reporting a drivers side recirculate blend door issue (B1242). Maybe its a cabin temperature sensor?

You have twisted the code description. There is only one recirculation door, and it physically is on the passenger side (it serves both sides of the car equally though).

B1242: Ford's Description: Air Inlet Door Actuator Circuit Failure.
Generic description: Air Flow Recirculation Door driver circuit failure. Note that "driver" does not refer to a side in the car, it refers to electronic component(s) in the DATC.
It is not directly related to the temperature problem, but it does indicate that your DATC is defective. It may also have faults related to temperature control.

There's no reason to guess at this and throw parts at it. There are trouble shooting steps that involve simple measurements to determine where the problems are. You don't give the year of your LS, so I'll just assume that it is a 2nd gen. Here's the 2nd gen troubleshooting for your problem.
2006 Lincoln LS Workshop Manual

 

[Crashtifer]

You have twisted the code description. There is only one recirculation door, and it physically is on the passenger side (it serves both sides of the car equally though).

B1242: Ford's Description: Air Inlet Door Actuator Circuit Failure.
Generic description: Air Flow Recirculation Door driver circuit failure. Note that "driver" does not refer to a side in the car, it refers to electronic component(s) in the DATC.
It is not directly related to the temperature problem, but it does indicate that your DATC is defective. It may also have faults related to temperature control.

There's no reason to guess at this and throw parts at it. There are trouble shooting steps that involve simple measurements to determine where the problems are. You don't give the year of your LS, so I'll just assume that it is a 2nd gen. Here's the 2nd gen troubleshooting for your problem.
2006 Lincoln LS Workshop Manual

I did indeed forget to mention the year of my car. Its a 2000 model. And thank you for pointing out my error, I did assume it meant the driver's side recirculation door. I'm fairly new to dual climate zones in a vehicle, so that's where my assumption is coming from. That and the fact the driver's side of my windshield sometimes fogs up in winter with the defrost on (air comes out of both sides of the defrost vent tho, but that's a problem for another time).

I did find somewhere in my research that trouble codes stored in the DATC can interfere with normal operation of the system. How do I clear the trouble codes? Both DATC units I ran the diagnostic on returned the same code.

 

[joegr]

The codes clear when you exit the DATC self test. Stored codes do not alter DATC operation (clearing them isn't going to change things).

The DATC module self-test through the front panel display

• can be initiated at any time. Normal operation of the system stops when the self-test is activated
• is entered by pressing the OFF and FLOOR buttons simultaneously and then pressing the AUTO button within two seconds. The display will show counts of 1 to 25 in the center of the display window. Record all DTCs displayed
• concludes by reporting all on-demand DTCs. Follow the diagnostics procedure given under ACTION in the DTC index for each DTC given.
• reports individual on-demand DTCs as four-digit DTCs (less the alpha character).
• will calibrate all the mode doors and check all analog inputs. The DATC module will only report on-demand (hard) faults that occurred while the DATC module was conducting its self-test.
• will light all control panel display segments if no faults are detected.
• will report individual on-demand DTCs without the °C symbol lit.

To exit the self-test, press any button.
This will clear all on-demand codes from the DATC module memory. If no button is pushed DTCs will continue to be displayed.



Upon exit from the self-test the DATC module returns to operational status.
The DATC module executes a hard (cold boot) reset which places the DATC system in the OFF mode.

Always exit the self-test before powering the system down (system turned OFF).

This thread may help you: GEN I - Understanding Climate Control System - No Heat Information

 

[Crashtifer]

joegr, thanks for that link. Its definitely helpful for anyone trying to figure out how these HVAC systems work. But seeing as the only code I'm consistently retrieving is related to a bad reciruclation door I'm just going to throw another DCCV at it and see if it remedies the issue. It'll be the third in 3 years but from what I'm seeing it's a somewhat common thing.

 

[joegr]

I used an aftermarket (Murray, I think) DCCV once because I needed one that night and that's all that was available here. It went maybe a month before it started blasting hot air periodically. I replaced with Motorcraft, and haven't had a problem since. The original one failed at over 100K miles, and I'm at nearly 200K miles now. The one on my 04 failed at about 70K miles, and the 04 is now at over 200K miles. In my experience, the real Motorcraft (made by Bosch, probably) valves last a very long time.

While, it is a little pain to change out a DCCV, remember that the other Fords used a air temperature blend door. That setup fails at about the same rate, but you usually have to remove the whole dash to replace it. That's a much bigger pain.

 

[Crashtifer]

I do believe Bosch makes the OEM DCCV for Ford. That issue aside, I got to try running my AC before the car warmed up today, and it seemed very luke warm until I held the engine at somewhere over 1500 rpm, then it started getting cool. I also noticed a lack of increasing rpms from the fan, which was running but didn't kick into a higher rpm when I turned on the AC. Is the hydraulic fan controller bad or is there something that controls it I should look into first?

 

[joegr]

I do believe Bosch makes the OEM DCCV for Ford. That issue aside, I got to try running my AC before the car warmed up today, and it seemed very luke warm until I held the engine at somewhere over 1500 rpm, then it started getting cool. I also noticed a lack of increasing rpms from the fan, which was running but didn't kick into a higher rpm when I turned on the AC. Is the hydraulic fan controller bad or is there something that controls it I should look into first?

More information is needed to answer that question. The fan will only speed up if the high-side AC pressure goes up. If it is low, then it is correct for the fan to remain slow. I have seen a failure where the AC compressor only builds pressure at higher RPMs. I've heard that this is usually the scroll control valve, but being short of time, I just replaced the whole compressor.

Put a set of gauges on the AC. If at idle the high side pressure is below spec (and the low side pressure is at or above spec), then your problem is almost certainly the compressor. On the other hand, if the high side pressure is above spec (and the fan is slow), then the hydraulic fan system is the problem.

 

[Crashtifer]

More information is needed to answer that question. The fan will only speed up if the high-side AC pressure goes up. If it is low, then it is correct for the fan to remain slow. I have seen a failure where the AC compressor only builds pressure at higher RPMs. I've heard that this is usually the scroll control valve, but being short of time, I just replaced the whole compressor.

Put a set of gauges on the AC. If at idle the high side pressure is below spec (and the low side pressure is at or above spec), then your problem is almost certainly the compressor. On the other hand, if the high side pressure is above spec (and the fan is slow), then the hydraulic fan system is the problem.

The compressor is brand new (not a remanufactured unit) installed this past weekend and only ran in the shop by the mechanic. They also replaced my AC drier and manifold hose assembly along with clearing the line with a conditioner, so I know for certain there aren't any obstructions. The fan isn't changing rpms at all, it just maintains a constant speed with or without the AC running. Last time my AC worked the fan would kick on high with the AC running.

 

[joegr]

Again, if your AC isn't building high side pressure, it won't speed the fan up. The fan reacts to the high-side AC pressure.
Put gauges on and find out, or just start throwing parts at it. The compressor that failed this way on me was brand new, only installed for a month or so.

 

[Crashtifer]

Well it appears to still have an obstruction in the system. I the checked pressures. High side maintains a constant pressure (120ish psi) while the low side maintians 20psi or drops to 0 with engine rpms. Adding a small can of R134 only boosted low side psi up a few points. It was fully charged by the shop when I had the work done, and I took it back today before testing pressures, and they found no leaks.

 

[joegr]

I'm going the guess the condenser, since the high side is lowish, and the low side is very low (assuming that it really is correctly charged). It's not possible to flush R-134a condensers.
Alternately, it might be the dryer, but you did change that, right?

I don't think that 120 PSI is enough to cause the fan to speed up much.

 

[Crashtifer]

Well I messed with it some more, charged it to 50psi and still no change, revved it, checked low side and it had dropped pressure but the high side hadn't changed. So I alternated between slightly overcharging and revving a few times then suddenly my high shot up to 450psi and low side went down to 60+ (at its lowest point) and the compressor started cycling every time the high side hit 450psi. I discharged some R134 and got the low side to 40-50ish psi, then suddenly it drops to around 20 while it still cycles to 450 the drops to about 180psi on the high side before kicking on again. Is that normal when the low side is at 30-40psi? I'm getting ready to make a run for another small can of R134 to bring it back up. I should point out it's kicking between max. pressure and shutting off about every 5 seconds or so, then it'll stop after about 5 minutes, then back to the 5 second cycles.

Outside ambient temperature reported by the car is 78 degrees. Inside the car the air coming out of the vents is hovering around 70-72 degrees with the way it is now. And the fan is now cycling it's rpms as one would expect.

 

[milehighmikey]

The cycling is a self protection mechanism for overcharged systems. Your system is dangerously out of control and there is no real way to tell what is inside the system now.

 

[Crashtifer]

The cycling is a self protection mechanism for overcharged systems. Your system is dangerously out of control and there is no real way to tell what is inside the system now.

I was thinking as much since I never remembered it behaving like that last time it worked properly. I'm quite sure now that the obstruction that worked itself free has jammed itself into my expansion valve. The system quickly pressurizes to 450psi on the high side then slowly falls while the low side actually registers a vaccum then slowly climbs up to just above 0psi. So yea, its bugged beyond what I can afford to fix, probably so even before I started troubleshooting this weekend.