S320 AC problems
 

On my 95 S320, the AC compressor does not engage. I can turn both sides of the CCU to Lo, and still nothing. As far as I know, when I do that, the clutch should engage at any temp. Today when I looked at it, it was 8 degrees C outside.
I dont' know if this is related, but the instrument cluster isn't showing outside temp all the time. Happens intermittently.

Got 2 codes from the CCU when I checked. E045 and E075.
Is it possible that my R134a is just low, and that caused my E045 code?? How can I check the pressure if the clutch won't engage?? If I hook my AC gauges to it, which side does each line go to?? I have red, blue, and yellow lines. Yellow, I believe goes to the bottle I'm filling from, iirc....

bump

Where did you get those codes from? They don't look right. A/C codes are usualy in the form of Eb1 xxx. Use the procedure here to get the A/C codes and post what you find.

That link is for the E class W210. His is different (but similar). Those codes are right for his car.

Current sensor values: Set temperature wheels to white area. Igniton ON. Press left and right AUTO button. Wait at least 20 seconds then press REST for >5 seconds.

Scroll with left AUTO button to read current-sensor values. Write these down.

E045 is "refrigerant pressure sensor (B12), short circuit"
E075 is "Coolant circulation pump (A31m1), open or short circuit"

Yep. I had looked up the codes. The E075 has been around for a long time, but I still get proper heat. That doesn't seem to be a problem, although I might look at replacing the aux pump sometime soon here.
The AC pressure sensor is my concern right now. Could it just be that my pressure is low. When I looked through the code list, I didn't see a code for low refrigerant pressure. If the pressure is low, it's an easy fix, where as opening the system is a much harder fix.
I also don't have much of the equipment mentioned in the WIS to test, so I was wondering about homebrew testing....

I didn't look through the whole list of codes; I just looked for those that you mentioned.

Measuring the static refrigerant pressure is the next step. You'll want to use the blue hose, since it goes to the low pressure gauge. With the car stone-cold, connect it to the low-side fitting and read the pressure, and translate that to refrigerant temperature (this may be marked on your dial). It should read ambient. It will read lower if you are essentially out of refrigerant (no liquid left in the system) but could charge it. If it reads 0, you should replace the dryer as a minimum (after fixing the leak).

With the leaky evaporators known to be an issue on these cars (especially on the earlier models) checking refrigerant pressure is where I would start. A leaking evaporator will slowly exhaust the entire system of refrigerant and the low pressure shutoff switch will stop the compressor from self destructing. Did you notice a slowly creeping bad performance in the system before the compressor would no longer engage?

Evaporator replacement on these cars is a bit on the expensive side as it requires the complete removal of the dash which is labor intensive. I have read about some owners using "leak stop" additives to prolong the replacement with varying degrees of success and failure.

In most of the time that I have owned this car, I have not used the A/C that much. It worked last summer the 3 times I can remember using it. It's been fairly cold around here lately. It woudl be getting close to a year ago that I last used it. It could have leaked down, and I just didn't notice.....
Another possible problem or symptom I noticed while my sister was driving the car today was that I didn't seem to be getting any major amounts of heat on the passenger side. The drivers side was set a few degrees cooler, and was much hotter. The passenger side was only blowing moderately warm air.
Duovalve perhaps?? Or the aux pump??

bump

again, bump....

Do you have pressure in the system?

Ac or coolant system?? Haven't had time to check either. Hopefully tomorrow morning.
Grabbed another duovalve out of the wrecked S420. Hopefully one side is good in it, and I can swap it into the one I have.

As I understand it, it's a common occurrance to get a 075 error on these cars. I replaced my duo-valve at a considerable expense to try to get rid of the code, and got the code back within a few days of the installation. I've been told on more than one occasion "don't worry about it as long as your heat works correctly."

If you've got unbalanced heat, the duo-valve is where I'd start.

To confirm, you can also check under the hood while the car is at operating temp - there are two hoses coming from the heater core (engine coolant flows into the core in a single pipe and exits to the duo-valve through two pipes). Having an infrared thermometer helps, but you can test it with your hand if you're careful. The pipes run along the bulkhead to the right of the throttle actuator. They're about 1/2" (26cm) in diameter. See if one is noticeably different in temp than the other. If so, either the duo-valve is malfunctioning and not allowing the coolant to flow out of that side of the heater core, or you've got a blockage.

Pulling sensor values will also help. Dials to white - CC on. Press and hold Rest for 5+ seconds. Cycle through the codes with the left Auto button. Register 3 is the left heater core temp, register 4 is the right heater core temp. If the temps say the same, then likely the sensor for the right core (if the right side is the one that's cooler in the car) is defective and the CC thinks the temp is right.

to run the sensor values, do I ahve to have the car running, or shut off with the key in the on position?? I'm assuming it needs to be running....

I checked out the heat. from cold, sensor 3 and 4 were saying +/- degree of what my infrared thermometer said the temp in the car said it was.
After I warmed the car up with the heaters on max, register 3 said it was about 70C, and the passenger side was saying 35-37.
I checked the hoses off the duovalve. the bottom outside (side closest to the fender) hose and the center hose were about 35C, and the bottom inside hose, and the top hose were 70-80C. I'm thinking the duovlave is at fault. I picked up a second one from the junkyard. I figure if I take that apart, and take a good side from it, my heat should work again.
Haven't checked the A/C pressure yet. The low pressure fitting is in the front, right next to the ac cooler, isn't it??

NO!!!!! That's the high-side line!

The low fitting is in the line between the evaporator and compressor, in the engine compartment.

You said that your compressor wasn't engaging. That means that even if you do have a duovalve problem, you also have an AC problem.

Thanks for the correction on which fitting... I figured the duovalve and A/C problems were separate.... Now, I heard that unplugging the duovalve causes the heat to be at high all the time. Which plug or both??

I checked the pressure in the low valve. it read 60 psi, and the compressor started today when I started the car, set all the dials to 'lo', and turned the economy off. Might my ac problem have to do with the outside temp sensor that seems to display on my dash intermittently??
Btw, the gauge was reading about 15 psi before I put it on the car. Dad said it was reading the ambient pressure in the atmosphere.

The gauge reads PSIG, or pressure above ambient, so if it read 15 before you hooked it up, it would mean that you really have 45 in the system.

For AC work, only vacuum is ever measured as absolute pressure (in microns of Hg). Otherwise, it's PSIG (G is for "gauge").

45 PSIG is very low unless it was rather cold at the time.

it was about 18 C at the time, but I didn't have the car running. I guess I'll have to get a can or 2 of R134a and filler' up....

What is the correct pressure for that system on the low side while the car is running?? I can't seem to find that info anywhere.....

That information is in the FSM. There is a set of charts, where you look up the values depending on several variables, the biggest of which is the ambient temperature.

But the low-side pressure alone is not enough information to ensure that you have a proper charge. You really need the high-side pressure if you're not doing it right and recharging by weight.

Could you post the chart?? I can't seem to find that in any of my stuff. Looks like I'll have to buy the adapter for the high side as well.

Actually, I thought I had the cart for that car, but my (paper) manual somehow omits it. It's not even listed in the contents for that section. It has everything but that chart for the 140 through MY1995.

Maybe someone else has a different manual, or even an electronic copy with the chart. There is one in my 210 FSM DVD, for example, but that's a different car.

I've looked through alldatadiy. Nothing on pressures, only weights. The only thing it ways is to check the sight glass and fill till there are no more bubbles.....

How hard is it to suck the whole system out, and put r12 or r14 in there.....

It's not that it's hard to recover your current refrigerant. The problem is that it requires tools that few DIYers possess.

It is always best to recover and recharge by weight. The FSM for my 210 does give a pressure chart, but it says to use it to confirm proper operation of the refrigeration system if there seem to be problems once you have filled it to specs.

I could recover, but I couldn't recharge it by weight. at least not from what I took out. Can one after taking the R134a out of the system, and put in r12??
I might try to fill it with the sight glass system..... might work.....
Should I try to get the stealership to give me a pressure chart??

I have a 30 pound can of r12a kicking around. That's why I"m asking about swaping gases....

No, do not put any R12 in there if it came with 134a as they use different oils. Sell that to someone with an older car (or keep it around for the future for your own older car). I recently paid $90 for a 30# cylinder of 134a.

not R12, it's R12a. Duracool. Here is the link....
http://www.deepfreezeinc.ca/faq.htm
I vacuumed out he system today. I can't get cans of R134a in Canada.
I use it on a bunch of the farm equipment and such for ac refills... and some of the older vehicles... R134 is almost impossible to get here....

I think we're about to find out how well hydrocarbons work in 134a systems, and not just from you. Still, don't mix the gasses and be sure of the oil miscibility. Your car came with PAG oil.

If you use hydrocarbons, do not "release" some of the vacuum before charging. You don't "release" a vacuum. Instead, the act is letting air in. Air contains moisture, and moisture will polymerize with the oil.

I did pull vacuum on the system. 10 in hg, as was specified on the duracool website. (I did this with a hand pump meant for brake bleeding and vac testing. Can you tell I want cold air in my car???????) Then I added 3 of the small cans through the low pressure port. After running the system on LO while stationary, it went right down to 48F according to the cabin temp air sensors. After the car sat like that idling for 20 min, the temp was 52F. ( was filling a sprayer during that time). Then I took the car out on the highway, and at 70 mph, the core's temps were registering 39-40F. Now, we'll see how long the system works like that.
FYI, the pressure of the refrigerant was just over 60 psi, while the guage empty was 15. Seems the pressure requirements are much less with this product to get the same temp drop.....
Will keep updated....

A/C Problem
 

Blue is low side, Red is Hi side, yellow is for filling bottle or vaccuum pump. Also you might want to check this site out it has a great setup to help you troubleshoot your problem. http://www.eclassbenz.com/node/27 Hope it helps.

10" is not much of a vacuum, and not enough to boil any water out at all. I really don't think much of their instructions to add air to the system. And not pulling a real vacuum is the SAME THING as adding air!

I guess we'll see what happens.....

So, now continues the saga of the heat. As it can get cold here at night (6C the other night), I want my heat working.
So, I ran the following tests. I pulled the plug off the duovalve. The three wire plug. I then started the car and turned the heat to min. I then took an electrical tester, and put the ground in the center and checked the outside connectors. It was reading just about 12 volts. I then checked the resistance on the duovalve. It was somewhere around .015 ohms for both sides. Next, I checked the pump at both sides of the connector. Read about 13v. so, I shut the car off, and got a 12v battery, and some jumpers. The motor ran when I hooked it up, and both sides seemed to click when I connected the jumpers to them. It was hard to hear, but that seemed to be a case. I'm starting to think that it's just a bad rubber inside.
A few weeks ago, I picked a spare up at a scrapyard for $175. I ran all the same tests. The click for both sides was audible, and the motor ran properly. So, I closed random valves and blew through them (I don't like the taste of antifreeze), and some seemed the close when power was applied to them. Both sides seemed to operate properly. I guess I'll just pull the old one out, and put the other one in. I'll take the one that in my car now apart and see if I can find a way to repair the rubber inside....

I installed the new to me duovalve tonight. Seems to work just fine. Temps on both sides were about 77-78C according to the sensors.
Will keep updated.

Junkyard duovalve still working. Not hot enough out to see if the AC is still working. I had to charge last summer, and overcharged a bit.
I evacuated here a few weeks ago, and put in a weighted charge to keep the defrost working properly...
MattL, The 10" that was recommended was for a system that was still sealed, and you were just sucking out the old refrigerant. They recommend 29" if a system has been opened.
Before anyone says anything about using r134a, it's almost impossible for a diy guy to get it. You can only buy 50 pound bottles, and I heard it's a 4 month course to get certified to buy the stuff. Shop wanted $300 just to do a charge, and that didn't include any leak detection. Leak detection would have cost in the down payment on a new S classe territory.
The government in Canada where I live is phasing out R134a. R12 is beyond impossible to get, and trying to bring a can across the boarder is jail time. Trying to bring across the small cans of R134a without certification can net more time in the clink than arms smuggling from what a customs officer I asked told me.
I get very uncomfortable at temps above 22C and even in temps above 28-32C depending on humidity. My body isn't conditioned to deal with heat. I deal much better with temps around freezing. So, no ac isn't really an option.... For those of you in the south, that would be like telling you to go without a heater around 3C. I'm perfectly fine with that with just a long sleeved shirt or light jacket. Most of the people from the deep southern US would show signs of hypothermia...
As for the fire hazard, it's there. It's the position we're in...
There are no special fittings required by Canadian law. Just must be labeled. Which is done. It's not illegal in any Canadian province to use a hydrocarbon as a refrigerant.
Rather than arguing about what should and shouldn't be used, I"m just playing the hand I've been dealt to the best of my abilities.