'95 Eagle Vision Air Conditioning

Can anyone point me at resources for troublshooting the air
conditioning in my '95 Eagle Vision?

A copy of troubleshooting pages from a manual would be helpful ( I
don't presently have a manual ) .

The compressor isn't cycling on, and I need to know what the circuit
that controls it looks like so I can check to see whether I've got
broken wires, or a sensor that's not operating properly.

I'm thinking it's probably something electrical/control related,
because when I had problems with my '94 Voyager leaking, even when it
was empty and I needed to add R134a, the compressor would cycle on so
that I could begin the process of adding refrigerant.

 

A properly designed AC system will not turn on the compressor when the refrigerant has leaked out. When you add a small about of refrigerant to the low pressure side the pressure will increase enough for the compressor to come on.

 

The compressor clutch is activated via the compressor clutch relay in
the power distribution box in the engine bay at the driver's side
fender. This relay is in turn picked based on input from the A/C
pressure transducer located at the bottom passenger side of the
condenser, evaporator temperature sensor, and pushbutton or automatic
temperature setting.

If the pressure is too low, then the relay will not activate. The
relay also will not activate or will not de-activate if the evaporator
temp sensor is flaky. This is the problem in my case. I bypassed all
this and connected a dash switch to directly activate the relay.
Downside is that I have to cycle manually to de-ice the evaporator.

In your case, first check that there is enough pressure in the system.
If yes, check the pressure transducer and see if it conducts.

 

First your assumption is flawed. All modern A/C systems have a low
pressure switch that cuts the compressor off if their is not
sufficient pressure in the system. Many times if the system is very
low the compressor will cycle on and off quickly but a flat empty
system will not.

Locate the low pressure switch on yours and jump it with a wire lead
or paperclip. Usually they are somewhere around or on the accumulator
but I am not familiar with your particular car so I can't give you an
exact location. Once you jump the switch the compressor should come
on. Don't run it that way for long if it works or you will ruin your
compressor!

If the compressor still doesn't come on you will need to check for 12v
and trace it back through the system to find the problem. If it does
come on you are going to need to find the source of the leak and
repair it, replace the dryer and have the system evacuated/recharged.

Steve B.

 

Thanks for the direction. I'll let you know how I make out once I
track down my multimeter.

I love the internet. Where else would I find answers so quickly!

 

When I did connect a can of refrigerant (with dye and sealer, so that
it can be tested), two things happened:

- I discovered my charging hose had a leak, so I'll have to get
another one.
- the compressor didn't cycle on.

So I'll have to pursue the electrical avenue, and get a new charging
hose. I notice that you can now get them with a guage on them.

 

http://www.aircondition.com/wwwboard/

and/or

http://www.autoacforum.com/categories.cfm?catid=2

 

now the real bad news!!!!
the sealer is made to react with air so when it hits the air outside of the leak it seals and the leaks stops but when the sealer contacts the air in the system then it seals off hoses compressors and other internal parts rendering the
whole system junk and i'm starting more and more of this junk do it
we now have to have a 2000.00 tool to tell us techs when sealer is mixed in the systems so we do not contaminate other's systems and render equipment useless
my dealer just paid 1500.00 to have one recycle machine repaired

 

The first thing I'd do is put a pressure guage on it. If this car
hasn't had an AC evaporator replaced, then its probably lost all its
R-134a. The early LH cars had a lot of trouble with corroding the
evaporator coil due to the materials changes needed for R-134a.

The AC will NOT turn on until there is some minimum pressure in the
system. When charging the system with refrigerant, the vapor pressure of
the R-134a in the charging system pushes enough into the system to allow
the compressor to kick on and complete the charging process.

 

The first level of diagnosis is complete.

I picked up a pressure guage at Walmart and checked the low side
pressure. That's OK at a little over 60 PSI. I followed all the
hoses around looking for a pressure switch on the low side of the
system and didn't find any. The low side hose went from the manifold
on top of the compressor to the H-Block. The other side of the
H-Block ran to the condensor. The only pressure switch I saw was on
the line going from the high side of the compressor, so I'm presuming
that would be to keep the system from overpressurizing and turn the
compressor off.

Is there any other pressure switch on the low side? Perhaps inside
the car? What do I have to take apart to get to it?

If I had a pinout on the Relay socket, what would I expect to see
there? Does anyone have a pinout that shows this?

 

I'm quite well acquainted with the evaporator core issue. However,
I'm pretty sure the previous owner (my neighbor) told me they had
already done that replacement early on. I asked specifically because
I know of the issues with the lousy brittle design. I replaced one
myself in the '94 Voyager we had; it was only four years old! Penny
wise and pound foolish engineers and penny pinchers!

I did put a pressure guage on it today, and the low side reads about
60 PSI, whcih should be more than adequate.

I'm trying to figure out what the problem could be. What are the
potential trouble points?

- leaks -- not likely in this case since we've got pressure
- electrical - a possibility, but I don't have a diagram to help me
diagnose things. I had recurring issues with the A/C wiring in a VW I
had because the bulk of the wires got routed near the battery and
corroded.
- sensors
- high pressure - this is one I don't think I want to bypass, so
I'll have to have someone check the pressure. How does this sensor
report high pressure? Open or closed?
- low pressure - is there a sensor? Where is is located if there is
one.
- evap temp - I'm presuming this is going to want to shut things
down if the evap ices up
- are there any others?
- blocked H-Block - How to diagnose this? Wouldn't this result in
excessive pressure in the high side of the circuit? I presume the
sensor on the high pressure line from the compressor to the condensor
would show high pressure and shut things down. I'm thinking this is
the most likely thing.

What next?

- get someone to put a guage on the high side
- check the high pressure switch
- locate a low pressure switch if there is one.

 

I don't remember off the top of my head where the low-side pressure
switch is. As far as electrical trouble-spots, have you checked the A/C
compressor relay in the relay box (drivers side inner fender). The
relays all interchange, so you can pull out a known-good relay (like,
say, the high-beam headlamp relay) and swap it in place of any relay
that you're suspicious of.

 

Go over to http://www.aircondition.com/wwwboard/ and ask your questions
there. The guys there are quite knowledgeable and helpful. It's a great
source of A/C info.