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calbiker
09-06-2013, 09:09 PM
The A/C output is warm air. The compressor spins when A/C is on. I though the system may need a freon boost.

The low/high pressure before and after recharge (one 9.5 oz can of R-134a):

26 psi, 125 psi
36 psi, 240 psi

The '06 Sprinter manual on page 24-65 states pressure should be 250 psi at 80F ambient. I *think* I got the high side pressure correct. The manual also says to measure the evaporator inlet and outlet tubes temperature. I'm reading 93F and 122F. It should be a lot lower. It's not cooling!

DAD shows no ATC faults. Can DAD actually read ATC faults?

I want to measure the A/C Pressure Transducer voltage. It not possible to stick a wire into the connector to access this voltage. The connectors have a tight fit. How do you measure sensor voltages? Poke sharp needle into the wire insulation?

Any troubleshooting ideas?

'06 3500

Cal

riskydnb
09-06-2013, 09:18 PM
Recover all refrigerant, vacuum down for 30min hold for 4min at negative pressure to see if there are any leaks. Add 1.9 lbs. Most likely its a bad HVAC panel or heater shut off valve. But probably an HVAC control panel. I have them for sale remanufactured for $200 plus $75 refundable core with a 1 year warranty. Low side should be around 50 psi and hi around 250 psi. Call me if interested, 760-622-0148 -Randy

calbiker
09-06-2013, 10:17 PM
I'll answer some of my own questions.

I poked a hole into the pressure transducer wire to measure voltage. With A/C on, voltage slowly rises from 1.4V to 2.2V in ~10 minutes. It may still rise, but I stopped test. This looks ok, as manual gives 0.451V to 4.519V as normal range.

I also disconnected the pressure transducer connecter. DAD did detect the error. So, it looks like DAD detects (some) A/C failures.

Risky- so you think it's the HVAC control panel. Dang, I was hoping it was something simple. Are there specific tests I can do to verify it's the control panel? I'm be interested in a replacement. I may have to go without A/C on my 7-week trip starting next week. Going through Texas to South Padre Island my get hot!

Cal

riskydnb
09-06-2013, 10:23 PM
I'll answer some of my own questions.

I poked a hole into the pressure transducer wire to measure voltage. With A/C on, voltage slowly rises from 1.4V to 2.2V in ~10 minutes. It may still rise, but I stopped test. This looks ok, as manual gives 0.451V to 4.519V as normal range.

I also disconnected the pressure transducer connecter. DAD did detect the error. So, it looks like DAD detects (some) A/C failures.

Risky- so you think it's the HVAC control panel. Dang, I was hoping it was something simple. Are there specific tests I can do to verify it's the control panel? I'm be interested in a replacement. I may have to go without A/C on my 7-week trip starting next week. Going through Texas to South Padre Island my get hot!

Cal

Im in Phoenix, will you be coming through here on your way to TX?

bc339
09-06-2013, 10:32 PM
The easiest test is to disconnect the single wire to the A/C compressor. With the engine running and A/C on, you should have 12 volts at the terminal.
If the pressure is good, the transducer is good, the A/C clutch should engage. If it doesn't the control panel is the culprit.

Bruce

riskydnb
09-06-2013, 10:34 PM
His compressor was spinning(working) It can only be the HVAC or heater shut off valve.

calbiker
09-06-2013, 10:48 PM
First stop is Prescott for a week of mountain biking. I can stop in Phoenix. How long does it take to remove the HVAC? Does it entail removing the coolant lines?

Im in Phoenix, will you be coming through here on your way to TX?

riskydnb
09-07-2013, 12:40 AM
First stop is Prescott for a week of mountain biking. I can stop in Phoenix. How long does it take to remove the HVAC? Does it entail removing the coolant lines?

10min job and no.

calbiker
09-07-2013, 01:18 AM
Glad it's just 10 min. But I'm having problems getting the center instrument panel off. I got the top left screw off, the two screws in the middle out, the ashtray out (2 screws), and the shift lever frame trim off. Something up top is keeping the center bezel in place. What am I missing?

Thanks
Cal

bc339
09-07-2013, 04:49 AM
There are four fasteners that hold the housing on (not including the ashtray assembly). Look inside on the right side, in about the same area as the upper left side fastener. It will also help to place the shift lever in Neutral.

Bruce

riskydnb
09-07-2013, 04:58 AM
theres also a screw under the square box that you would keep your change in.

calbiker
09-07-2013, 02:43 PM
I don't have a square box. The lower section of the center console lifts out about an inch. The top remains firmly in place.

http://i429.photobucket.com/albums/qq12/Calbiker/Misc/P1080089_zps14d198f1.jpg

bc339
09-07-2013, 03:29 PM
Your center console switch plate is very different from mine. The instruction from the service manual directs you to remove the fastener at the bottom middle and to use a trim tool to release the plate. You can release it without the trim tool by working from the bottom middle and carefully lifting along the sides as you move up, releasing the plate. The top edge will hinge out.
Are you able to lift up the bottom edge to see if there is a fastener there?

Bruce

calbiker
09-07-2013, 04:50 PM
OK, making progress. I got the bottom and side fasteners undone. The bottom middle won't budge. Looking up from the ashtray vacated hole, I see a screw that's next to the rectangular coin box. From the photo above, it looks like the rectangular box slides out to get access to the screw. Unfortunately, I have this chrome looking plastic that's also molded down around the coin box, preventing it's removal. It appears I need to pry the chrome looking plastic off first. It's glued down. Is that the correct procedure?

Cal

Edit, removed chrome plastic, then pulled coin box out and removed last screw. On to removing center bezel.

calbiker
09-08-2013, 12:27 AM
I got the automatic temperature control module out and did some measurements.

The module has 2 temp sensors connected to it. Measurements are with no A/C and with A/C on and a few minutes on run time:

Air outlet temp sensor (C1-16, BR/GY): 3.2V; 3.42V
Evaporator temp sensor (C1-13, BR/DG): 0.70V; 1.12V

The evaporator temp sensor voltage seems out of line (if they're the same type of sensor).

For comparison, the ambient temp sensor (the one outside by the license plate) reads 77F and 2.1V.

Is the "heater shutoff valve" also known as the "water cycle valve control"? The water cycle valve control wire (C1-5, BR/VT) has 13.7V on it, regardless of the temp control knob position. Seems like the manual says this line should be modulated to maintain a specific heating temperature. Even though a voltmeter is a crude tool to detect modulation, the fact that I read a constant 13.7V regardless of temperature setting does indicate there's no modulation. What's this voltage supposed to be when A/C is on?

Are there any tests I can do to pinpoint the failed component?

Cal

bc339
09-08-2013, 12:58 AM
The water valve is powered closed and receives a PWM (pulsed width modulation) signal. The manual states if it is not full open, it is pulsed by the ATC in periods of 4 seconds. The manual does not list any specifications for values at the various settings. An o-scope would be the best tool to tell you if it is really modulating.
Have you tried reading the voltage at the compressor wire when the ATC A/C switch is engaged?

Bruce

calbiker
09-09-2013, 01:32 AM
After further testing, it looks like the water cycle valve is functional. The signal from the ATC module does pwm cycles. When the signal is at 13V then the valve is closed. Temperature measurements at the solenoid verified the valve is not stuck open.

The compressor clutch control signal is also functional. When the A/C is activated, this signal has 13V and the compressor begins to spin. Earlier tests also showed the high pressure A/C line is at 240 psi. The compressor must be functional.

As far as I can see, the ATC module controls the A/C by way of the compressor signal. Since this signal is functional, I don't see how the ATC module can be defective.

I don't know what the temperatures to the two evaporator lines are supposed to be, but I read 90F for the big line and 120F for the skinny line. There's no cooling what so ever. I also read about 90F at the A/C vent.

Cal

bc339
09-09-2013, 03:08 AM
I read you first posts with the high and low pressures, have they changed?
If the compressor is engaged and stays engaged, there are a couple of things to look at.

The water valve is receiving the signal to close, but may have failed mechanically, allowing hot water through to the heater core.

With the A/C running does the evaporator line get cold and sweat? If not, the expansion valve may have failed. Low suction pressure will indicate that the expansion valve may have failed.

Bruce

calbiker
09-09-2013, 05:05 PM
Regarding the water valve: With the vehicle cold, I started it up and monitored the 3 rubber hoses entering the valve. The hose in front and the upper hose coming off the back side of the solenoid increase equally in temperature as the engine warms up. The lower hose attached to the back side of the solenoid remains cool. It's not clear to me where the two backside hoses go.

I don't know what's normal, but retesting the pressures gave interesting results. Right after A/C turn-on: low = 30 & high = 65 psi. The pressures slowly increased. After 25 minutes: low = 35 & high = 155 psi. Voltage at the pressure transducer after turn-on is 1.09V and after 25 min 1.65V.

One of the two pipes after the expansion valve (going to the evaporator) does sweat. Using my HF infrared thermometer (which incidentally reads high), I measure 62F on one line and 86F on the other. On the other side of the expansion valve, I measure 81F on the fat pipe and 102F on the skinnier pipe. Outside ambient temp is 67F.

Cal

bc339
09-10-2013, 03:03 AM
In the service manual, take a look at page 24-5 for your condition.
It looks like refrigerant is not going through the evaporator, either the evaporator is blocked or the expansion valve is stuck (see page 24-74 for expansion valve) - I would go with this condition:

The low side pressure is normal or slightly low, and the high side pressure is too low.

1. Low refrigerant system charge.
2. Refrigerant flow through the A/C evaporator is restricted.
3. Faulty A/C compressor.

Also see page 24-65 for the Compressor Discharge Pressure Chart as well as the procedure for the partial charge method for testing the system . Based on your ambient pressure of 67 F, you should have about 215 psi on the high side.

By the way, the small diameter tubing is the high pressure line, the large diameter one is the lower pressure or suction/return line. This also applies to hydraulic lines.

If you end up looking for a blockage in the evaporator, I would recommend changing the expansion valve and the drier while the system is evacuated. They are about $40.00 apiece and are fairly simple to change.

Bruce

calbiker
09-11-2013, 03:48 PM
Thanks for your help Bruce. I'm going to call it quits for now as I need to prepare for my trip next week. Though possible, it's hard to believe there's blockage. I hardly use the A/C. It has at most 20 hours on it. I don't like to travel where it's hot. Texas in October should be OK.; for sure the Gulf Coast & South Padre Island.

Cal

Aqua Puttana
09-12-2013, 11:57 AM
Thanks for your help Bruce. I'm going to call it quits for now as I need to prepare for my trip next week. Though possible, it's hard to believe there's blockage. I hardly use the A/C. It has at most 20 hours on it. I don't like to travel where it's hot. Texas in October should be OK.; for sure the Gulf Coast & South Padre Island.

Cal
I wouldn't ignore the possibility of a low charge just yet. It may be worth throwing a gauge on it and adding just a bit of freon. If it helps you can take it from there.

Not scientific, but easy to try. You may find that having A/C is handy in sometimes often humid Tejas. :2cents: vic

calbiker
09-12-2013, 06:23 PM
I actually did that. My very first step was to charge the A/C to a pressure I thought was appropriate. The can still had about 20% of R-134a left, so yesterday I emptied the rest of the can into the A/C. After the charge, pressures went to 36 psi and 230 psi at 71 F ambient.

The A/C did start to work (a little). Vent air went down to 65F. But the high pressure line keep increasing and also the line temperature (above 100 F). Vent temperature then goes up.

My problem is that I don't know enough about A/C systems. Is it normal for the high pressure line to get this hot? I'm also wondering when the high pressure pipe gets so hot, shouldn't the front electric fan turn on? This fan does work. When I unplug the high pressure sensor connector the fan turns on.

It's tough for a DIY type-of-guy to take it into a shop. But if it gets hot enough, I may humble myself and do just that. Otherwise, I'll read up on A/C principles and tackle the problem when I get back. I get the feeling the answer is staring at me but I'm not seeing it.

Cal

I wouldn't ignore the possibility of a low charge just yet. It may be worth throwing a gauge on it and adding just a bit of freon. If it helps you can take it from there.
vic

lindenengineering
09-12-2013, 09:10 PM
:laughing:Whoa Whao!

First to be able to trouble shoot and repair A/C systems you need to have some training in HVAC systems. Frankly not knowing enough can get you into some expensive repair issues. You can even get injured in the process so be careful!

First you MUST have the correct charge, guessing it as you have experienced has got you nowhere!
For a TIN model and the front A/C system there is 1.90 lbs in the system. Not much room for guesswork I am afraid.
The only way to achieve this is to get the system evacuated and drawn down into a deep vacuum----around 25"HG. This will remove not only the refrigerant, but moisture and air that may be in the system from doing what you have done so far. Remember air doesn't like moving temperature about, in fact its a good insulator. Moisture in the system will cause and internal freeze up and scupper the job! Equally those cans of instant A/C fix have oil in them and the correct amount of oil is essential as it will, also insulate the system internally if too much., Then again to little and the system can run low on oil flow and wreck itself.

To get to this stage you need to go to a shop that does A/C systems even a Jiffy Lube type place and have them get it right. For around 45 to 70 green ones you are then on the road to fixing it.

Now once charged the system will stall for a few seconds upon start up if all is working well and then the low side will start to drop to about 40 psi and the high side will start to elevate towards 300 psi. The system works just like the Freightliner big rig that pulls up beside you and grumbles its 14 litres "hi fellow Freighty/Dodgie truck or screeches a slipping fan belt seeing a vanity MB badge up there!"
:lol:
But in any case with all of 'em the condenser fan will kick in at between 300/350 psi and around 80dgf ambient within a few minutes of operation. In colder climates it will take a bit more but it will get there. With the fan running (if the condenser fan is good, yank the binary switch socket off while running to fool the fan relay if in doubt--It will activate the fan for a short while)
It will operate until the hi side has dropped to about 200psi. The low side will go down to about 30/35psi and you will get cold air out of the vents. There is a relationship to pressure and temp so if you see 35 in the Lo side it near that inside the evaporator.
Now make sure your condenser is clean and the same goes for the Evap and pollen filter. Air flow is the name of the game, remember you are dealing with Boyles Law P1 P2 P3 and all that!!
It doesn't have to be a boil on your neck!
Hope that helps
Dennis

calbiker
09-12-2013, 09:35 PM
I wouldn't say that. I when by the book! You may want to refer to it.

The service manual states you can do a partial charge. At 70 F ambient, high pressure should be 220 psi; at 80 F pressure is 250 psi. That's what I was aiming for and that's about what I got. No need for any laughing.

Cal

:laughing:Whoa Whao!

First you MUST have the correct charge, guessing it as you have experienced has got you nowhere!

MillionMileSprinter
09-12-2013, 10:56 PM
I struggled with A/C issues with 2 different sprinters (the ones in my avitar) and never got them sorted out in my driveway. Mind you, I feel pretty confident with a wrench, but the A/C humbled me. I ended up going to a shop and for (I believe) 120$ they evacuated the system and recharged it. Viola! Cold air. I probably spent around 100$ in getting r134 in cans and a set of A/C gauges and countless hours reading and working and charging and basically wasting time. To this day I still can't figure out what I was doing wrong, but have come to the conclusion that I'll leave the A/C work to the shop and do everything else myself.
...so don't beat yourself up over it.
Just my two cents.

Aqua Puttana
09-12-2013, 11:38 PM
:laughing:Whoa Whao!

...Dennis
I believe Dennis is correct.

I am one of those generalists that knows enough to be dangerous.

I was going on the most recent discussions about a possible plugged evaporator. IF the charge was low and affecting the line temperatures as you said, then adding a bit of freon might have changed those things and gotten us off the plugged evaporator direction.

I know enough to know that is very difficult to charge a system properly by using gauge pressures. As Dennis said, the measured charge is the way to go. If you have already been adding freon then it is very easy to get things out of whack. :2cents:

Sorry for any confusion. vic

lindenengineering
09-13-2013, 02:09 AM
Guys
Just a few points.
If you are referring to any German translated MB manuals or other German vehicles for that matter the author assumes you know what you are doing and in this case that you are trained HVAC technician. Indeed there is label on the radiator core support informing you of the same.

On the other side you cannot buy refrigerant and self dispense it; hence it is "verbotten" so DIY issues are not the on the thought curriculum in the Eurozone.

Now the shot of refrigerant as you have mentioned specifically is a prescribed method of getting a reaction or not from the system , its an aid to diagnosis if you are trained and know what to look for, and yes we HVAC techs use that methodology at times to pinpoint a problem. But then we use other techniques as well to gauge system reaction like ice on the expansion valve and hose pipe water flow on the condenser to get reactions to the change in state of the refrigerant at points in the system especially where a refrigerant gaseous state becomes a liquid and "vickey verky".

Now as a DIY'er you can do a lot to keep the system in good shape.
Clean the condenser AND the radiator plus the intercooler bolted in front of the radiator core.
A good air flow over these matrix-es is essential for controlled high side pressures. Plus of course it keeps your engine cooling in good shape as well. Pay particular attention the area behind the condenser fan. There is a dead zone there and dirt collects on the condenser the enemy of an efficient system.
Don't be tempted to blast the cores with a high pressure garden hose it will bend the cooling fins. I use a foaming coil cleaner by Zep for the job. Heavily encrusted matrixes need a de-greaser and some elbow grease by you can buy a more aggressive cleaner from a HVAC supplier. As a licensed Pro (EPA 601/602) I buy various supplies from these folk but I am sure they would sell you coil cleaner should you need some.
http://www.sidharvey.com/public/product.htm

The same goes for the evaporator, AND the pollen filter, there must be good air flow through the system for it to cool.

Now buying those cans of refrigerant from auto parts stores is risque!
One its often a cocktail and the contents is not pure. Furthermore there is often some air in the mix plus lots of oil and a sealant. So injecting that stuff into your system invites all sorts of issues that turn into curve balls that make the system act very strange. You often won't have a cat in hells chance of getting a success.

Nowadays the refrigerant charge is very important even a couple of ozs out can affect the way the system reactions, worse so on the later Sprinter models.

Now as with anything you need to baseline a system to get into the precision area of HVAC repairs. That means an accurate set of equipment to get the RIGHT amount of refrigerant charge into the system. From that point you can start diagnosing what is going on.

Frankly there are no short cuts to fixing A/C systems, the result is often short lived success!
In the world of MV repairs a customer will get very angry if there is an A/C comeback.
So it has to be precise A/C repairs every time to justify my bull like repair bill to some!
Dennis

Dougflas
09-13-2013, 08:33 PM
25" of vacuum may be correct for Colorado but 29+" is required for locations at sea level. To the original poster....your system holds 1 lb 14oz of R134a full charge. Evacuationg for one hour means nothing. To do the job correctly, you should have a micron guage connected. Most AC shops do not use this. (it's sad). With no micron guage, over night evacuations are safer. Then put in the correct amount with the PROPER proceedures. Now you have eliminated the most common mobile AC problem...incorrect charge. If your system still does not operate correctly, troubleshoot from this point.

lindenengineering
09-14-2013, 05:02 AM
Basically I mention "around 25" of HG because some folk do have older vacuum machines and such at their disposal.

Yes older machines would just about develop 25" at 6500" above sea level.

Most of us now have the later machines that have greater capture and recovery abilities and drawn systems down very quickly to 29" HG, even at our altitude.

As for overnight evacuations these activities often have to take the high road in the light of customer expediency. Most customers want a quick turn around and fix which dictates the practices conducted in most shops.

In any case as you quite rightly mention the majority of faults are caused by insufficient refrigerant charge or someone has pumped too much into the system.
Dennis

Dougflas
09-15-2013, 11:08 AM
Yes Dennis, I agree that clients want the job done quickly and most shops can not spend the needed time to evacuate properly. Pulling to 29Hg means nothing. There is still moisture in the system. The only way to eliminate this is thru the use of a micron guage. Shops would be amazed how long it takes to evacuate to 500 microns if they were to use a micron guage.

Aqua Puttana
09-15-2013, 01:08 PM
...Shops would be amazed how long it takes to evacuate to 500 microns if they were to use a micron guage.
I worked with chillers used to liquify chlorine gas. It took more than low vacuum alone to evacuate a system. Some sweeps with dry nitrogen would be used to remove the moisture. In the case of those large systems I believe the N2 use was necessary because of the amount of moisture and probably some other reasons, although it did speed up the time.

N2 isn't that expensive if you are looking to decrease the time needed to dry the system. That said, it may be a common practice. I am not that familiar with smaller system recovery/evacuation. vic