A/C woes - the $1200 Evaporator RNR

The evaporator is really a pretty big job to replace. In sense you have to drop the whole dash and remove the HVAC duck work to get to it, it's time consuming. Then there is the job of charging the AC system correctly, and since the system was open to the air/moisture, the shop probably put it under vacuum longer to rid the system of moisture. At least any good shop would.

If you want an idea of what they needed to do to replace the evaporator, take a look at this article I did on replacing a heater core. It's going to be along the same lines since the evaporator is in the same box.
BaystateGearheads • View topic - 87-93 Mustang Heater core replacement

According to Alldata, the Evaporator is dealer list at $248.98, which seems excessively high to me. The labor times for just replacing the evaporator is listed at 5.4 hours which does not include 1.4 hours for refrigerant recovery, evac/pump down and recharge of the AC system.

I don't see fox verts being anywhere near as collectible as a 60s vert, but that aside. I would drop the dash and replace the evaporator and heater core if its still the original piece yourself. Then take it to a shop and have them vacuum down the system and have it charged. If you are prepared to sit on it then waiting to do the work yourself shouldn't be an issue. Make no doubt, its a big job, but its tedious rather than overly difficult. Doing it yourself will save you close to a grand.

Mustang5L5 said:

Maybe I got lucky, but I just looked up the evap core I purchased for my '88 a which back.

Bought it on amazon.com from a seller called "rem art auto parts" and paid $24.56 for a brand new in box evap core.

Here's the kicker. I bought it as an aftermarket part, it showed up sealed in the manufacturers box. I pull it out of the box, and sure as he'll it had "ford motorcraft" stamped all over it....for $25

I dunno if I got lucky or what...but I'll take that deal any day.

Let me see if I can find the part number of what I bought

Edit: 4 seasons. P/n 54521

Came in a box with the logo and pn...but had motor craft stamped on it. Did a search...not seeing any others for $25

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That is awesome, you could have made a killing collecting them for $25.

They are easy to get to. Just lots of screws that you gotta remember where they go. I've done a heater core and a blower fan on my 89 and I had the fan done in probably 2 hours.. I didn't have an ac system that I had to disconnect but other than that its practically the same process. Just do it yourself, take your time and take lots of pictures if you have to.

I have replace my entire system, all with parts from ackits.com. There site is great and sales guys are knowledgeable. They have the evap for $70. Sounds like your system is almost empty so you could have it fully discharged, replace the evap yourself then have it recharged by the shop. It should save yourself a lot of money that way. I wouldn't suggest charging it yourself as there are special tools and knowledge needed for this.

The evaporator P/N 54521 will be $79 at Advance Auto Parts.

Heater core replacement tech note: Mustang

R134a Air Conditioner Conversion and recharge instructions

Tools and materials you will need:

R134a = $7-$10 a can – takes 2 - 2 ½ cans.

R134a compatible oil = $5-$7 for an 8 oz bottle – better get 2 bottles.

Gauge set for recharging = $20-$120 – check out the pawn shops for a bargain before you pay retail.
See Harbor Freight Tools for an inexpensive gauge set.


Vacuum pump – I use an old refrigerator compressor = $20- $40 at used appliance stores, or go to the Dump and get one for free. Be sure to have some R12 compatible oil handy to keep it lubed up properly.


O ring seal kit = $8.

R134a charging can adapter = $13 (I cut mine up to use it with the R12 gauge set that I have had for a long time).

Plastic tools to disconnect refrigerant lines - 1/2" & 5/8" = $4 each.

Miscellaneous hoses and fittings to adapt the R134a adapter to the R12 gauge set = $15. If you buy an R134 gauge set you can skip this.

R134 Refrigerant charge is 26-28 Oz plus 6-8 Oz of PAG 100 oil.

Conversion Instructions:
Keep in mind that to fulfill the requirements of the EPA, you are required by law to recover any refrigerant that still remains in the system. How (or wither or not) you accomplish this is up to you. Connect the charging gauge hoses to the service ports on the A/C (red gauge = high pressure, blue gauge = low pressure) and open the valves on the gauges to dump the remaining refrigerant (if any) into your "freon recovery system", whatever it may be. Disconnect the charging gauges since you are finished with them until you are ready to fill the system with R134a.

Next comes the changing of all the old "O" rings so that the chances for leaks is minimized. Use the plastic connector tools to separate the lines, place the extended collar part of the tool so that it faces the large part of the connector and push inwards: this expands the spring so that you can pull the tube apart. You may need a helper to push on the tool while you pull on the tubes to separate them. Install the new "O" rings: be sure to coat them with new oil when you put them in. Install the new dryer/receiver, R134a service port adapter, compressor, add about more 4oz of oil to high pressure line and tighten up all the lines. Close the hood, start the engine, let everything get warm under the hood, but don’t add the R134a or turn the A/C on. Connect the charging gauge hoses to the service ports on the A/C (red gauge = high pressure, blue gauge = low pressure) and open both valves, then connect the center hose to the vacuum pump. The purpose of this exercise is to heat up the system so that when you vacuum it all down (yes, you will need a vacuum pump- mine is an old refrigerator compressor), that all the air, vapor and moisture from the cleaning fluid vaporizes and is removed from the system. Vacuum it down for about 30 minutes, this should give you about 28" of vacuum or more inside the A/C system. I have a vacuum gauge "T" connected into the vacuum pump line so that I can accurately watch the vacuuming process. This is a good time to take a soda and sandwich break since it doesn’t go faster if you watch it.

Typical low pressure side R134 coupling


Typical high pressure side R134 coupling



Charging instructions:
Remove the electrical connector from the dryer/receiver and jumper the two connections inside the wiring harness side of the connector together: this allows the compressor to engage in spite of low pressure/no gas in the system. Close both charging gauge valves, and then disconnect the center hose of the charging gauges from the vacuum pump and connect it to the R134a can tapper. Put the R134a can in the can tapper and screw it down with the can tapper valve closed, then open the valve. Loosen the hose at the center connection of the charging gauge set until the R134a squirts out: this purges the line of air and moisture. The refrigerant is added through the low pressure side of the system, so open the low pressure gauge valve to add the R134a. Start the car and take note of the idle speed, then set the idle speed up to about 1200-1500 rpm, and turn the A/C on inside and set the fan speed on high. Watch for the pressure on the low side to drop off as you are filling, and the R134a can will get warm and stay warm. This tells you the current can is empty and needs to be changed for a fresh one. Before you disconnect the can, be sure to close the valve on the R134a can tapper.

Watch the high side pressure on the charging gages and regulate the adding of gas to keep the high side pressure under 350 psi. You will probably need a fan in front of the car to keep the readings below 350 psi. I had to put the R134a can in hot water while I was charging the system with it, or else the can got so cold that it quit flowing. Use caution when you do this so that you don’t get water in the charging adapter when you change the cans. When you have added the 2 cans of gas, the high side will read about 250-300 psi and low side about 28-38 psi. Turn the idle speed back to where it was, turn the A/C off, disconnect the charging gauges, and re-install all the caps on the service ports. Remove the jumper from the low pressure switch harness and plug it back on the switch connectors.

The above technical note is for informational purposes only, and the end user is responsible for any damages or injury. The end user bears all responsibility for proper recovery/disposal of any R12 refrigerant.

Mustang5L5 said:

It has been mentioned to me a few times that once the system is opened, you should change the accumulator bottle. Reason being the drying agents inside will begin to suck in moisture rendering them useless.

For a leaking that has moisture inside, this could also be the case. I've read that pulling a vacuum for 24 hour or more can restore it.

Needless to say, I bought anew bottle and hose. Was $60 or so anyway.

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Is school during AC class we pulled a vacuum on a pickle jar full of water. It's actually pretty cool to see the water boil when subject to a vacuum. Obviously this is an excessive amount of water, but still shows you how the process works. And I agree, its easier to replace the accumulator, which may be part of the shops charge too in this specific case.