My wife is HOT! - PeachParts Mercedes-Benz Forum

jbambis · #1 06-16-2009, 11:06 PM

My wife's AC has been out for about a year now. About a month ago I paid a Mechanic to do a diagnostic and he said there was a leak in the evaporator core. So I spent about 40 hours replacing the evaporator core and expansion valve. Recharged the AC and it is still blowing warm - hot air. Any thoughts on what may be causing this? Thanks. Oh, we are dealing with a 1993 300E

79Mercy · #2 06-16-2009, 11:08 PM

we need more details. Is the compresssor runing? Does the low side hose get cold? Is coolant leaking into the heater core?

Your wife should be HOT. LOL

jbambis · #3 06-16-2009, 11:11 PM

How do I find out if the compressor is running or not? And how do I find out if coolant is leaking into the heater core? Do I have to pull the dash apart again? I checked the bottom hose and it is hot not cold. Everything under the hood is hot. We are in Dallas and it has been in the upper 90's for the last couple weeks...

pawoSD · #4 06-16-2009, 11:44 PM

Its easy to tell if the compressor engages. For one, you can see the "economy" gauge move over to towards the red a bit when you switch to the A/C mode on the climate control...as it adds a bit of load to the engine.

You can also look in the engine compartment and see the compressor engage, and hear it too. It should make a click noise when the clutch engages.

jbambis · #5 06-17-2009, 01:25 AM

It appears that the compressor is working, when turning the climate control on and off the engine surges. However the hoses are all hot, I can feel the coolant runing through the heater hoses. Just trying to throw out ideas in my head here... Would a bad thermostat have anything to do with this issue? It seems like something is hendering the system from getting cool. When I turn the CC dial from cool to hot it get's really hot and the 2 middle vents shut off.

pawoSD · #6 06-17-2009, 02:15 AM

If the return line (by the auxiliary water pump on the passenger side of the engine compartment) is getting hot....that means coolant is circulating....could be a bad switchover valve by the battery, or perhaps the climate unit in the dash is malfunctioning and allowing the valve to operate/let hot coolant through the heater core. If none of the A/C lines are getting cold though, that might mean low refrigerant....

Cal Learner · #7 06-17-2009, 06:22 AM

When the A/C system was recharged after repair work, were both low and high side pressure readings taken? It may be low on refrigerant, but if it were too low, the compressor wouldn't engage. So we need pressure readings. You're certainly going to want to do that before you even consider replacing the CCU.

Mr Project · #8 06-17-2009, 08:03 AM

Should probably make sure the basics are covered here as well. Since it sounds like you did the A/C evap. replacement yourself, did you charge it yourself as well? Did you replace the drier? Did you evacuate the system first? Did it hold a vacuum? How much refrigerant and oil did you recharge it with?

jbambis · #9 06-17-2009, 08:42 PM

I did do the evap replacement myself. I don't know alot about MB or AC for that matter but I do know how to use a wrench and enjoy working on vehicles. Honestly I don't have a lot of money to throw into this car right now (who does?) and don't want to just start replacing parts that don't need replacing and don't want to keep paying $75 to have the mechanic do a diagnostic and have me fix the wrong parts. Prior to doing the evap core replacement I took the car down to my mechanic and had him evacuate the system. After completion I had him recharge it. He tested it for leaks and pressure at that time but did not give me the readings, I figure if something was wrong he would have said something at that time. I did not replace the AC drier. The car is also having electrical issues with the interior dash and console lights. See my other post... w124 tail light problem

Could this be related to the AC not functioning properly? This car seems to have alot of issues, my wife loves the car and just want's it fixed. Easier said than done!

gmercoleza · #10 06-17-2009, 08:44 PM

Sounds to me like the TXV is stuck open. You need to put a set of gauges on there and report back with pressures before we can go any further. The rest is just speculation.

79Mercy · #11 06-17-2009, 08:46 PM

well you did recharge it after the evap replacement right?

jbambis · #12 06-17-2009, 09:00 PM

Quote:

Originally Posted by gmercoleza

Sounds to me like the TXV is stuck open. You need to put a set of gauges on there and report back with pressures before we can go any further. The rest is just speculation.

So I am assuming that the "TXV" is a valve? That would make sense. Where do I find this valve and how do I go about checking the pressure with a gague? Is this something fairly easy to do or should I not even bother and take it to the mechanic?

jbambis · #13 06-17-2009, 09:01 PM

Quote:

Originally Posted by 79Mercy

well you did recharge it after the evap replacement right?

Yes

79Mercy · #14 06-17-2009, 09:01 PM

just get a cheap low side pressure gauge from autozone or like store and connect it to the low side fitting.

#15 06-18-2009, 02:57 AM

OP,

Don't get the cart in front of the horse. You need to buy, beg or borrow a gauge set and take low side and high side pressure readings, record these along with the ambient temperature and post this information here. Without this information we are flying blind.

Take readings with system turned on wide open, throttle at about 1,500 RPM and give it 5 minutes for stabilization. It would REALLY be good to use a good fan in front of the car to simulate ram air while you take readings.