View Full Version : A/C evaporator, '93 6.5 C2500
I found out, much to my dismay, using my leak detector that the a/c evaporator is leaking on my '93 C2500. I replaced one years ago on an '85 1/2 ton Chevy pickup and it was a terrible job to do. I have the factory serv. manual for the '93 and this evap. replacement_really_looks like the job from hell. :mad: If anyone has done this job on a '93 or similar and have any tricks, advice, shortcuts etc. I'd be everlastingly grateful to hear of it.
Pretty much it.
The heater case has to come out and split apart.
The nasty part is the dash has to come out.
Yank the cluster, the radio, Glove box etc.
Once the dash is out, unbolt the case from the engine side of the firewall.
Once out, split the case and replace the evap core.
Hint ****
While your in there, toss in a heater core too :)
Yeah, good idea on the heater core. And the recirc. door actuator died a while back too and I'll do that. Do you know if there is a table somewhere that shows how much oil I need to put into the evap. and the accumulator when it goes back together? I didn't see that info. in the service manual.
The 93 uses R12, DO YOU HAVE IT ?? or has the rig been converted to R134 ??
About 4 ounces of oil in the accum. will suffice.
If you are using 134 pag oil is fine, if 12 then you need the mineral oil.
The evap itself should not retain much oil.
Be sure to suck the system into a good vacuum for about 30 minutes prior to charging.
If not you run the risk of having the orifice clog with ice if the system gets any moisture in it while its open.
Dvldog8793
05-31-2015, 05:32
Howdy
A couple other things to do "while you're there"...
I would replace all the dash lights with new even if they are not burned out.
Check the headlight switch for burned/heat damaged connections.
The resistor pack for the blower motor, cheap part that fails.
Replace or rebuild the plastic connector to the blower fan as it will probably be burned and heat damaged.
When I did mine, I also coated all the visible firewall with rubberized undercoating to make things just a little quieter.
If you have ever thought of upgrading the sound system, now is the time.
If you need a new windshield(cracks, chips, leaks or gravel pitting) The job can be easier with the glass out.
Have fun!
Well, it_ain't_going to be fun. But I very much appreciate the info on the oil quantity Robyn. And I like that idea about undercoating behind the firewall and doing the dash lights too DvlDog (68-72, Semper Fi) . Going to start on it Tues. and all the parts will be in tomorrow. Retired a few months ago from 45 yrs. as an airline mech. and I was hoping I wouldn't have to tackle this kind of aggravation ever again. So it goes.:(
a5150nut
05-31-2015, 11:01
Well, it_ain't_going to be fun. But I very much appreciate the info on the oil quantity Robyn. And I like that idea about undercoating behind the firewall and doing the dash lights too DvlDog (68-72, Semper Fi) . Going to start on it Tues. and all the parts will be in tomorrow. Retired a few months ago from 45 yrs. as an airline mech. and I was hoping I wouldn't have to tackle this kind of aggravation ever again. So it goes.:(
Now it's not aggravation, it's a hobby!
That's really the right attitude, isn't it? Thanks.:)
Got the a/c and heating module reinstalled today finally with new evap., heater core, blower motor resistor and recirc. actuator. Got two new GM factory heater hoses and a new GM high press. a/c tube that goes from the condenser to the evap. That line was badly frozen on where it attached to the evap. and the threads peeled out when I finally got it off. I'm posting this as I'm confused at the orifice tube configuration on this truck. I'm not a novice with auto a/c and had my own sideline business doing car a/c when I worked in Saudi Arabia years ago. Every GM clutch cycling orifice tube system I've ever seen had the orifice tube located in the inlet to the evap. where the liquid Freon line attached to the bottom of the evaporator. On this truck it's located at the exit of the condenser and at the opposite end of the line that goes from the condenser to the evaporator. This line is not insulated in any way. So, effectively it's carrying the expanding droplets of liquid/gas from the orifice tube and absorbing heat for about 3 ft. of it's length through the engine compartment before it gets to the evaporator. :confused: I cannot figure out why GM would design it this way? The old leaking evaporator did not have the crimped section in the bottom high pressure inlet to mount the orifice tube. However, the replacement evaporator does. Does anyone more knowledgeable than myself see a problem if I relocate the orifice tube to the normal location? I converted the system to R-134A several years ago and put in the higher efficiency, (more cooling surface), condenser at that time. Any advice or help would be appreciated. Thanks.
Will finish this thread as I finally found the answer to my question about the orifice tube location. GM moved it to the condenser outlet to "prevent refrigerant and compressor noise in the cab." In the unlikely event that someone was as confused about it as I was. :)
I ran into a problem a few years ago when replacing a condenser coil on my 95 Suburban. I did not notice the orifice tube in the condenser and when I got everything back together I could not get the front air to work right. The rear air worked great. When you have rear air the orifice tube for the front air is located after the Y where the front and back lines connect. The rear air uses an expansion valve so this is why I had my problem. After I removed the orifice tube in the condenser outlet everything was fine. I always thought that I was sent the condenser for a non rear air unit.
Very interesting.
I had always thought that the orifice tube was right in the inlet to the evaporator as was the case for most auto units.
Nice to know the true story
Thanks for sharing
It is that way on my 1994 Suburban and even in Phoenix, Arizona, when correctly charged and working correctly, the AC blows nice and cold. That being said, your point about the cold coolant running through a hot engine compartment is solid. However, from my limited knowledge of Thermodynamics, heat in the system is heat. Moving the orifice won't improve the performance significantly. Whether the extra heat comes into the system before the orifice or after does not really matter. The extra heat is still in the system and the condenser must be able to shed it. Also remember that the condenser then sheds it's heat through the radiator and back into the engine compartment where the compressor, the hoses and the receiver dryer ar. It can be a bit of a vicious cycle if you know what I mean.
If you really want to improve performance, insulate the hoses and pipes carrying the R134, especially the metal pipe after the orifice to the evaporator. That is the pipe I insulated on mine. I used a sort of aluminum foil backed foam that wrapped right around the pipe.
Now as to the other components in the engine compartment, whether or not you insulate them depends on the temperature of each part. If, while the engine is running, they are hotter than the air blowing off of the back of the radiator, insulating them will hurt. If they are cooler, insulating them helps. My gut feeling is to just insulate the pipe from the orifice to the evaporator and you'll have decent temps.
Hope that helps! -Dave
Thanks so much for the time and help, Dave. Yes, it's good info. I had to replace that line that goes from the cond. to the evap. as the fitting to the evap. was completely frozen and ruined when I took it off. The new GM part is already partially insulated, but not well. I plan on covering that line. I put an aftermarket turbo, A-team, on the engine about a yr. ago and put a turbo blanket, exh. manifold blankets and header wrap on the crossover and downpipe then. I can tell it keeps the underhood temps lower. Just finished putting an intercooler on it two days ago, but that won't do much for underhood temps. Also did the hi flow water pump and dual thermostat mod. too. Hoping this good old truck will last me a few years now.
Sounds like you are well on the way!!! I'd love to see pics of the intercooler set up.
Sounds like you are well on the way!!! I'd love to see pics of the intercooler set up.
If you can give me a link that explains how to post a picture here, I'll be glad to do so. I've never posted any pictures on this forum.
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