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Topic: Dash A/C (Read 1132 times) previous topic - next topic

Dash A/C

We have a 2003 320.  Engine driven a/c  compressor will not engage.  No 12 volts to clutch - 12 volts in and out of sensor on compressor high side and condenser cooling fan operational.  There must be an a/c clutch relay somewhere.  I tried to call James on Friday, but he did not return my call.  Last year my dash air was working extremely well - ice cold.  Earlier this year, compressor would cycle quickly, run for maybe 40 seconds, off for 1 1/2 minutes.  I have not checked the high side, but I do have a low side gauge.  It reads 60 lbs., and when I hot-wire compressor, it slowly drops down to almost a vacuum.  If this system uses an expansion valve, I would suspect it is plugged.  If that is the case, how does one replace the expansion valve.  Obviousy, the evaporator is buried in the dashboard.  If the expansion valve is replaced, I think it would make sense to install an in-line filter in the liquid line as close to evaporator box as possible.  Anyone have any experience with this repair?

Gregory S
2003 Designer

Re: Dash A/C

Reply #1 –
Gregory,
Sounds like you got the diagnosis right.  If you replace the expansion valve, also replace the drier (usually located close to the condensor coil, mine is located behind the rear driver duallies).
 
The evaporator coil is behind the heater core and is difficult to get to as you have to do a lot of deconstructing of the dash.
 
Here are a couple pictures:
 
Peter & Beth Martin
No Forrest? What have you done?
MC# 15890 until Dec 2016; FMCA #F329677
Cincinnati, OH

Re: Dash A/C

Reply #2 –
Gregory,
You need to check your high side pressure and make sure that the pressure is above the normal and this will also confirm that the high pressure switch is working properly.
 Does your unit have a low pressure side pressure switch? If so make sure it is working.
Some of the systems have an inline filter that is in the hose where it is hooked up to the expansion valve.(some people have been charged for an expansion valve and the shop just puts in a new line strainer)
If you determine that the strainer or expansion valve is stopped up a change of the dryer is a must. You will also have to flush the lines to remove the desiccant that has contaminated the system.
It is a lot simpler to just pull the dash dog house apart to get to the valve. (Peter & Beth had a real good how to do this with pics. a couple of weeks ago)
After that just pull a vacuum, check for leaks, and recharge.
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Dash A/C

Reply #3 –
Thank you for your input.  My coach, upon inspection, does not have an expansion valve, per se.  It is what I recall seeing earlier in my automotive career as an expansion block assembly, with both high and low side hoses.  If this valve is bad, it will be very difficult to access.  I have found on the side of the evaporator case, what I recall to be a switch that turns the compressor on and off based on evaporator temperature.  Two wires, both hot, that come on with the rotary switch in max air or a/c position.  However, I still cannot get 12 volts to the compressor clutch.  Guess I'll have to wait for James.

Why doesn't Foretravel install a sight glass in the liquid line to check state of charge?  I think I'll install one.

Gregory S
2003  designer
 

Re: Dash A/C

Reply #4 –
Check the Bosch type relays if your set up still had them.  I had a similar problem.
Dwayne Keith
1992 U240
3116/MD3060