was that supposed to happen?

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

jmc - 06 Apr 2009 03:22 GMT

(2001 Dakota, 4.7l v8 engine. I've mentioned the AC before.)

Ok, so it's already known there's a leak somewheres in my AC system.
Mechanic recommended waiting until spring to fix it. I attempted to
fill it in the fall, went through a can and a half of refrigerant before
I gave it up as a bad job (gauge never read sufficient pressure).

Was able to use my defroster the entire winter with no probs until
Friday, when the motor started making noises again.

So, on this beautiful Sunday afternoon, I went back out with my can and
gauge, popped that lead off the cannister and shorted it, fired up the
truck and loaded more refrigerant. All was going as expected - the
gauge indicated slight increase in pressure but still not enuf - when
suddenly the truck made a noise like the AC came on - or off, or
something - and the pressure gauge shot up to full.

Was that supposed to happen? I immediately stopped, turned the truck
off, set all to rights - and heard an extended hissing like air escaping
in the engine - sounded like it was below where the low pressure valve
is, but closer to the engine block. Eventually it faded. When I fired
her back up, the AC - for now - is working properly. But why did it
suddenly... I'm not a mechanic you understand, so I'm not quite sure
*what* it suddenly did.

Last time I spent a lot more time trying to load r134a in, and the
engine/AC sound never changed the whole time. I've no idea if the fact
that it did this time is a good thing, or a bad thing!

Oh, and does $1500 to fix the leak, which I'm told is in something
behind the firewall(since I can't find dye around the engine block) a
fair price? Seems high to me.

Any advice appreciated!

Jodi

Reply to this Message

beekeep - 06 Apr 2009 10:08 GMT

>(2001 Dakota, 4.7l v8 engine. I've mentioned the AC before.)
>
[quoted text clipped - 32 lines]
>
>Jodi

I don't really know but am guessing that there is a low pressure switch in the
system. By adding refigerant you closed the switch and the compressor came on..

beekeep

Reply to this Message

Tom Lawrence - 06 Apr 2009 12:33 GMT

> I don't really know but am guessing that there is a low pressure switch in
> the
> system. By adding refigerant you closed the switch and the compressor
> came on..

Well, she shorted out the low pressure switch at first (that's the connector
she took off the accumulator).

Jodi, did the AC compressor kick on when you first shorted out the
low-pressure switch?

And the $1,500 charge is to remove the dash, and change out the A/C
evaporator - which are known to go bad and leak. $1,500's a little high for
that, though - usually it's about $1,000 or so. It is a lot of work
removing the dash - by the time they get it out, drain the coolant, recover
the A/C, get the heater box out and apart, swap the evaporator, put it all
back together, and re-fill coolant and A/C, it's probably taken them the
better part of the day.

Reply to this Message

jmc - 06 Apr 2009 12:48 GMT

Suddenly, without warning, Tom Lawrence exclaimed (4/6/2009 7:33 AM):

>> I don't really know but am guessing that there is a low pressure
>> switch in the
[quoted text clipped - 14 lines]
> put it all back together, and re-fill coolant and A/C, it's probably
> taken them the better part of the day.

Tom, thanks. When I did this in the fall, I knew the names of all the
parts I was working on, and why. Memory's horrid though but yes, I
shorted the low pressure switch to keep the AC from cycling on (or is it
off)? That's why I was so surprised when it did it anyway.

That's what I though - around $1,000. This is DC though, where Things
Are Very Expensive (just ask my cat, I've put $900 into her medical
bills this month, with another $700-900 to go). Or don't ask her -
she'll just tell you I haven't fed her yet (even if I have).

Who needs a mortgage? Medical bills for me, my cat, and my truck are
what's chewing into my nest egg. ::sigh::

jmc

Reply to this Message

Lyndell Thompson - 07 Apr 2009 02:37 GMT

The noise was the high pressure relief valve opening (usually is located on
or near thr compressor. Your orifice is problably partly clogged and your
suction pressure will be low. You added refrigerant to bring the suction
pressure up........it couldn't get to normal, so you overfilled it and the
relief valve blew. After the pressure is reduced the valve seals itself off
and lucky for you it sounds like the charge is about right or it would not
be cooling. FWIW I spent two weekends on my wife's cavalier installing a new
evaporator. I would be hard pressed to take on another one for $1500. I
don't know how a dakota would compare. I think it would be easier due to
more room. I am not a mechanic just a do it yourselfer (commercial
refrigeration servicman by trade). :-) If you decide to tackle the
evaporator you will have to obtain a manual (hardcopy or online) and find
the procedure for disabling the airbag system. If you get prying around
under the dash you may deploy the airbags. At that point you will care
little about the A/C. You will be paying a proffessional to repack the
airbags. Repair manuals don't cover this...........they all say: Seek
professional help in this matter. :-)
Good Luck Lyndell

> (2001 Dakota, 4.7l v8 engine. I've mentioned the AC before.)
>
[quoted text clipped - 32 lines]
>
> Jodi

Reply to this Message

jmc - 10 Apr 2009 02:58 GMT

Suddenly, without warning, Lyndell Thompson exclaimed (4/6/2009 9:37 PM):

>> (2001 Dakota, 4.7l v8 engine. I've mentioned the AC before.)

>> So, on this beautiful Sunday afternoon, I went back out with my can and
>> gauge, popped that lead off the cannister and shorted it, fired up the
[quoted text clipped - 8 lines]
>
> The noise was the high pressure relief valve opening (usually is

located on

> or near thr compressor. Your orifice is problably partly clogged and

your

> suction pressure will be low. You added refrigerant to bring the suction
> pressure up........it couldn't get to normal, so you overfilled it

and the

> relief valve blew. After the pressure is reduced the valve seals

itself off

> and lucky for you it sounds like the charge is about right or it

would not

> be cooling. FWIW I spent two weekends on my wife's cavalier

installing a new

> evaporator. I would be hard pressed to take on another one for $1500. I
> don't know how a dakota would compare. I think it would be easier due to
> more room. I am not a mechanic just a do it yourselfer (commercial
> refrigeration servicman by trade). :-) If you decide to tackle the
> evaporator you will have to obtain a manual (hardcopy or online) and

find

> the procedure for disabling the airbag system. If you get prying around
> under the dash you may deploy the airbags. At that point you will care
> little about the A/C. You will be paying a proffessional to repack the
> airbags. Repair manuals don't cover this...........they all say: Seek
> professional help in this matter. :-)
> Good Luck Lyndell

Cool, thank you for the explanation. I always like to know the "why" of
things. I have no intention of handling this myself, I can fix small
stuff but this is definitely outside my experience or comfort level!

I know my passenger side airbag has a way of disabling it using the key
(no babies so I've never tried it), but no idea if this is sufficient
for ripping the dash apart. I'll let my trusted mechanic worry about
that, it's apparent they've worked on Daks before and have also told me
this is a common enough problem with this truck.

Goes in Monday after next to get this fixed. I've lived hereabouts
summertime with a vehicle or two with no AC, but I'm not interested in
doing that any more :)

jmc

Reply to this Message