I was driving on the interstate last week with my defroster going (1999
Dodge Ram 1500 with 5.2L engine, manual tranny) when my windshield
starting fogging up severely. I had to open my window to get the
windshield to clear. I knew immediately my a/c was working properly.
I only have a Haynes service manual to go by and of course it not only
doesn't go very in depth on trouble shooting the a/c system, but the
schematics for the a/c clutch relay is not the same as the relay in my
truck. I did check the fuse (in the PDC under the hood) and substituted
relays from other circuits (identical part numbers) to no avail. Today,
I went out and tried jumping the cycling switch on the accumulator to
see if the clutch on the a/c compressor would energize (it did).
With this information, could someone tell me where to go from here to
troubleshoot? At this point, I'm figuring I've either lost the a/c
charge or the cycling switch is defective (but this is strictly a guess).
Right off it sounds like a leaking evap coil. I had to have mine
replaced on my 2000 Ram about two years ago. You can do it yourself,
but there is a lot of labor to it. Cost for replacement at a dealer
is about $1200.00, I got mine done by an independent for about
$600.00. Cost of the new coil is about $100.00. Good luck.
It's not a heating issue....when you turn your defrosters on, it also
turns on your a/c system to help get rid of the moisture. My a/c
compressor isn't kicking on the way it should. With the diagnostics
I've done so far, I'm thinking I'm probably low on refrigerant.
If it is a leaky evaporator, I'll replace it myself (unless there's
something tricky about it (and there shouldn't be) and have a garage
evacuate the system (requires a vacuum pump that I don't have). I
should be able to charge it myself. I used to be trained in HVAC
through the military, and at one time I was quite good. I was
responsible for the HVAC and refrigeration systems on Coast Guard
cutters. However, that was several years ago, and I've forgotten so much.
Thank you for the answers so far!
two ways to find out if it is leaking quckily
Put dye in the system (not reccomended)
Or get a electronic refrigerant detector.
If the detector smells refrigerant it will beep at you and closer you get to
the source the louder it gets.
Though you will still need to put gages on it to see it if has pressure in
Probably you've had a slow leak for a bit, and it finally got to the level
where the low-pressure cut-off switch popped. All that warm, humid air
blowing onto your windshield caused the fogging.
If you have a local shop with a R-134 detector, have them stick the probe in
the floor vents while you run the blower. When I recently had a suspected
leaking evaporator, I had a local shop verify this, which took all of two
Alternatively, you can get some recharge cans of R-134a, and some tracing
dye. Inject the dye into the system, followed by the 134. Run the A/C for
a couple of days, then take a black light to the system, and see where the
leak was. A leaking evaporator will show up at the condensate drain, on
whatever the water hits when it drains out (sometimes a suspension member,
sometimes a puddle on the ground).
And no, there's nothing complicated about replacing the evaporator - just a
big PITA. Once the system is evacuated, the cooling system has to be
drained (not completely - just enough to lower the level below that of the
heater hoses going through the firewall). In fact, I'd just put a bucket
under the firewall, disconnect the heater hoses, plug 'em, and blow some
compressed air into the heater core to clear it out.
The real fun comes in pulling the dash, though this job can be severely
shortened, as well. Remove the knee blocker panel, and remove the piece of
dash frame at the bottom, so that the steering column can drop freely. Drop
the column (two bolts hold it to the firewall mount) onto the seat. Remove
the five bolts along the defroster grids that hold the dash to the firewall,
and remove the two bolts behind the side kick panels. This will free up the
dash. You should have enough room to rest the passenger-side of the dash on
the seat, giving you enough room to access the HVAC unit. If not,
disconnect the wiring from the bulkhead connector (low on the driver's side)
and other surrounding connectors, remove the steering column connectors, and
any other wiring (radio antenna, etc)., and haul the dash out of the
No matter how you do it, it's not a particularly fun job.
Thank you for the replies. I ended up getting rid of most of my HVAC
equipment years ago, including an electronic leak detector. Like Tom
suggested, I believe there is a slow leak. At this stage of the trucks
life, I'm not going to pull the dash (shudder! Been there, done
that...). I did look at the system to see if there was something
obvious (oil traces, rock damage to the condensor, etc), but didn't see
anything. I think I'm going to buy some refrigerant, charge the system,
and see how long it lasts. If it goes rapidly, I'll think about plan
"b"; trying to find out where the leak is. At the price R134A is, I can
put a lot of refrigerant in before it's cost effective to put in big
money into it. For that matter, the refrigerant could be lost through
the seals of the compressor.
Tom Lawrence wrote:
the light, goggles, and dye. add the dye, recharge and then in about a
week , at night start looking for the leak. First place I would check
is the condensate drain coming out of the firewall, the other obvious
place is at the compressor seal.You can't miss a leak, it will show up
bright yellow/orange with the light. JMTCW
Maybe you can find someone with a set of gages for the new 134A,
and see what kind of pressures in the system. I've got gages and
some of the new non-freon 134A, but I remember we're a couple
hours drive away from each other.
Check your local auto parts store. I'm remembering a charge kit I
saw awhile back that had a cheap low side gage on it. I think the
new 134A is unrestricted, so that's not an issue. Amazing all the
AC stuff they have at auto parts stores.
Many of the older leak detectors won't detect the new 134A, so
you likely made a good choice to get rid of it years ago.
Christopher A. Young
You can't shout down a troll.
Does Dodge use a special size port adapter for charging the A/C? I
bought a kit to do it that included a gauge, hose and port connector (my
gauge manifold would require adapters to attach the hoses, plus an
adapter to pierce/use the can) and I busted the stupid plastic
connection as it was slightly too small to fit the charging port. I'll
get my money back, but I don't want to repeat it. If I need to go buy
the adapters for the gauge manifold, I'll do that....
Dave Young wrote:
No...I did the right port...as you said the one that's on the metal
line, had a black plastic cover over it (removed it to charge of
course!), just behind the radiator support on the passenger side. I
thought the plastic fitting on the refill kit was going on way tighter
than it should, then it cracked, and one of the parts that grip the
charging port came off the plastic fitting. Back when I did this kind
of thing occasionally, I bought adapters and stuff from NAPA. Probably
what I should do now.
Tom Lawrence wrote:
Put an AC gage on the low side, and see what the pressures are.
If zero, then you've lost your charge. Not sure about the new
stuff, but the vehicles I've serviced need about 35 PSIG to make
the compressor come on, and then it kicks off about 20 or 25
Christopher A. Young
You can't shout down a troll.
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