How hard is it to replace the evaporator?
This is a 92 that's been converted. I recently replaced the blower motor - do I need to take all that stuff back out again?
Thanks!
JP

What is wrong with the evaporator may I ask?

Unless you are sure it has a leak, then I shouldn't ask.

Phil

Phil - it's got a leak.
Art - that pic looks familier - I'm trying to avoid that trip again, although my recluctance to completely disasemble my brick (again)is mainly a concern over finding enough room to store all the parts and the time factor (I'm slow).
Jim - is that hearsay or do you have the T-shirt?
Anybody actually BTDT?

I think the consensus is correct. I may be recalling r and r'ing the evaporator in my 87, which has connectors on the evaporator. You will need the room created by removing the heater box to install the later model evaporator with the hard lines attached.

Hi JP,

It has been a while, but my recollection of the 91-93 240 evaporator, with its hard line connections, tells me you need to loosen up the heater box to withdraw it. That's more than just a blower motor job.

I changed the heater core in a 91 with that same evaporator, with the objective of not disturbing the refrigerant, and those hard line connections going through the firewall represented the primary challenge.

Heater Core job


--
Art Benstein near Baltimore

Everyone seems normal until you get to know them.

I'm pretty sure you can pull it out from the passenger side of the console after removing the lines. I don't think you have to pull the blower assembly.

I fitted the whole assembly from a '92 244 into my '82 245 this past summer. I split the case to install a new heater core I had and if I remember correctly you have to do the same thing for the evaporator. Also, since the hard lines from the evaporator go through the firewall panel at a 90 degree bend I don't think you'd be able to get them out with the heater box in the way. It's a pretty tight fit. I know this sounds like alot of work but I believe it's the best way. Good Luck!

Follow up question - if the evap has a leak, is there a need to have someone evacuate the system - or can I assume it's not charged anymore and just disconnect the fittings? Should I also replace the dryer accumulator, or have that done when I get it recharged? I'm not planning on recharging it myself, just replacing the evaporator. Thans, JP

What you mean to ask is…. Do I need to have my refrigerant recovered? Technically YES, if it has more than a minuscule amount. This is according to “rules”. This is mostly when connecting and disconnecting to the system.

It is “unlawful” to knowing discharged a system into the free air. When there is a true leak or an accident beyond your control. Then it falls under Forest Grump, “ SHEEET Happens”.

IF the evaporator had a leak or the leak is some where else. The refrigerant gets out. It can be empty or very low.

The compressor should not run. It is because the low pressure switch will not let the compressor run. There could be as little as 1/8 of the systems capacity left. Gas only, no liquid. Just crack the line loose and listen. Should be like a tire leak until all gone.

Moisture is the big enemy here. The rule of thumb is as long as the system is not “open” longer then 30 minutes the dryer does not need to be replaced.

In the case of an evaporator leak there is a twist to consider. When a crack or hole occurs there it is possible that water from the condensation can get sucked in. This can be a problem on your domestic appliances like refrigerators and freezers.

In the case of the automobile there is the low pressure switch which stops the compressor from running and pulling the evaporator into a vacuum.

If some one doesn’t over ride the switch for very long and the evaporator was dry there should not be a problem. Remembering as long as the system was at or above zero pressure and not “completely open” to atmospheric pressure for an extended length of time. The dryer can handle it.

A good vacuum evacuation and using a heat gun on the accumulator/dryer should drive out and suck any moisture when you are ready to recharge the system.

I have had totally “wet” systems where I vacuumed for days and change dryers twice to get back to a dry system. Wet means several drops of moisture.

I doubt you have got that problem if your system has been treated normally. You will still have to have it vacuumed to get air out. Air has moisture and is considered a non condensable gas, in the same space. It is an application of Dalton’s law we have to contend with.

Moisture can freeze as it goes thru the metering device and stop the flow of refrigerant, thus cooling. On electric motor compressors that suffer a burn out it will combine with the resins of the insulation and can create an acid. Without water there can be no acid. That is why the refrigeration trade and my self become frankly, anal about it.
Car systems are considered in a high temperature and mechanical driven class. A lot less problematic but still have the same issues.


You can open the lines to get the evaporator out. I would recommend applying, aluminum foiled tape solidly over the ends of the lines to the rest of the system. Do not unplug the lines of the new evaporator until ready to connect it to the accumulator and high side line. The evaporator may have a slight pressure inside to keep goodies out when you pull the plug.

It is important that you keep dirt or other debris from entering the system.

Good luck in your endeavor.

Phil

Phil:
Thanks for the info, that is some good stuff.
The car has been w/o A/C for 4 months. Shortly after I changed the blower motor, the A/C stopped cooling, and the shop diagnosed leaking evaporater. Didn't have the $, so we've been using the 440 A/C. Now I'm ready, but want to save some $ by doing all the "fun" stuff myself. My thoughts are the system (at least at the evap) must be at or close to atmospheric pressure, so there's little left to leak out. My plan is to get the new evap, take the car apart, disconnect the lines (use the foil tape), install the evap, re-connect the lines, put the car back together, drive to to the local A/C shop and request them to evac and recharge, letting them know I just replaced the evap. Hopefully they will do what you suggested to insure the system is dry. Any thoughts or suggestions on this much appreciated. Thanks, JP

I would have to say four months could seem like a long time.

Since the diagnosis was a leak in the evaporator. That would mean they put enough gas in to bring the system up to at least 70 psi. Or there was enough gas already present of 70 psi to set off their leak detector. The system may have had gas in there for the whole time. By them adding some, helped keep the bad stuff out. Either way, I’m thinking with you. The opening must be small and it appears to be a good sign that nothing got in or is minimal.

Standard procedure is to pull a vacuum for 30 minutes and let the system set closed for a minimum of 10 minutes without a rise on the vacuum gauge. If it rises you have a leak somewhere in the system or possibly the connections at the gauge and extraction ports.

A micron vacuum gage tells shows if it is dry or not. I sincerely doubt that they have one. They rely on their manifold gauge set. 28 inches of vacuum is the minimum.

Because the automobile system uses rubber hoses they can never pull a deep enough vacuum to boil the water off. That is why I add heat to locations that moisture will migrate to or be trapped. The dryer is number one. Then, any area that appears colder than the ambient temperature of the entire system.

As far as your concern about were the gas pressure is the most. Unless the metering device is plugged or the compressor valves are perfect at sealing the pressure in the system will be equal everywhere “at rest”. The system will equalize.

The final note you may need to know is about the charging of the system. Your system a ’92 utilizes a fixed metering device. It does not modulate. This requires that the charge be weighed to the ounce for optimal performance. There is not a sight glass to watch to tell when enough liquid has stacked up behind the expansion device.

Gauge pressures are useless. If they charge by gauges only, they are guessing. You do not know when there is too much liquid until both sides are too full. The pressures become too high on both sides. Then it’s about taking some out. Ah! How much? Might ask to see what type of measuring device they use. There are two. If they don't have one I would leave!

To have a simplified term, I’ll say.
In order to put a fire out it takes liquid. Not enough liquid, you don’t move enough heat. If you can’t move it back and forth inside then it is the same. It’s a yin and yang system.

All this is not hard to learn. This was my second career for me. Becoming a machinist was a lot more involved. I can say I never learned all that there is to learn in that trade. Refrigeration was a snap.

You should try community colleges or trade schools. A second skill came in handy for me. Good R&D jobs and their benefits left the country like some 25 years ago now. I wasn't getting any younger and a major metropolis area was not the card deck I was willing to cut a deal with any longer.

Thanks and good luck

Phil