A/C Expansion Valve Clogged - Quick Fix?

The A/C on my 88TR stopped working last fall. The dealer thinks that some of the desiccant from the drier filter is clogging the expansion valve. Their solution is to replace the expansion valve, but as you know, that requires that virtually all of the dash and related stuff has to come out - with an accompanying very large bill.

Is there any way to solve this without taking everything apart? Does the evaporator assembly have a check valve in it allowing flow only towards the compressor? If not, can you remove the line at the compressor and at the drier filter and blow compressed air backwards through the assembly to clear it?

 

I would ask your dealer to flush the system first with a flushing agent, it may well shift the blockage, if not then you may well end up replacing the valve.

 

Do you have any facts from them such as hi and lo pressures? Does the system actually function at all? With the many common problems in the electrics, I assume that they have been checked? Is there a history to preclude this failure- is it still R12 or R134? This is all a factor in diagnosis and the subsequent repair. And yes, a reverse flush can sometimes help, buut the evaporator valve must be removed along with the drier to flush the system.

lots of points to look at before OKing the big one!

Later, Brian

 

I do not have the high or low pressures.

The system appears to function properly - the clutch on the compressor cycles on, then (I assume) the high pressure cuts it off after a few seconds. Fan and all works properly but no cold air at all.

Still R12

When you say "evaporator valve", is that what they call the expansion valve?

I'm not looking for perfect operation - just enough so that I can use the car in the summer. I plan to redo the dash next year when I'll have the space and time to do it all leisurely, so I'm trying to come up with a workaround that will carry me through this hot season.

 

the fact that it all seems to be working but not getting cold is a sure sign that the expansion valve is clogged and unfortunately the only cure that I have seen is replacement.As I said on a previous thread,This is very common on TR's.Why?,I dont know. Tim.

 

I have cleared these blockages many times. You will need a flushing agent (solvent) made for A/C systems and a device for which to introduce the solvent into the system. I use a flushing tool that is available from NAPA. I can get you numbers next week if you need them. A quart of the solvent is poured into a high pressure aluminum bottle, sealed and charged with about 130 lbs. of compressed air. On the bottom of the bottle is a fitting with a hose and rubber tipped air blower. Remove the lines on the receiver/drier and throw the drier away. Attach a hose over the end of the output hose of the receiver/drier with a hose clamp and run the other end into a bucket or suitable container. Remove the low pressure hose from the A/C compressor. Be sure to wear eye protection. Now using the blower on the hose of the solvent tank, sealing the nozzle tip into the end of the hose, you will blow the solvent into the system. After you have emptied the tank of solvent, use compressed air with reduced pressure, about 40 - 60 lbs. to blow through the system until nothing else come out of the other end. Sometimes you may have to do this a second time to remove the old oil and desitent from the system. Install new receiver/drier, evacuate and charge system then check for leaks. The first TR that I had to clear the blockage, I removed the expansion valve. BIG job. Quickly figure out that this way works just as well.

 

Thank you so much!

I would love to have any specific details (model numbers, solvent name, etc.) - this definitely sounds like the way to go vs. dash teardown

 

Try this link:

http://www.napaonline.com/cgi-bin/ncommerce3/ExecMacro/NAPAonline/search_results_product_detail.d2w/report?prrfnbr=28621785&prmenbr=5806&usrcommgrpid=

I'll have to get the flush part # tomorrow at work.

 

I will definitely be saving this suggestion by Mr.Ferrarioldman and keeping it in mind when the next plugged expansion valve comes in.It sounds feasable to me .
Thanks.

 

Some are tougher than others to clear but I haven't had one that didn't clear yet. The flush that I use is called Dura 141 NAPA part numbers 409517 for the gallon can and 409518 for the quart can. I use a clear hose on the output side that goes into a bucket so that I can tell when the all the yucky stuff comes out.

 

Tom, GREAT technique. When I was investigating why my "new" 19,661 mile Mondial t Coupe wasn't cooling, and the manifold gauges registered a VACUUM on the low side when the compressor came on, I thought I'd be diving into the center console to at least remove the expansion valve to clear the inlet screen of drier residue.

After following your flush advice (I did get a trace in my eyes and should have worn gloves), it works like a champ and I'm headed off to Blowing Rock for the weekend in 90 degree heat cool as a cucumber with just a drier and some R-12.

Thanks for a great tech tip!

-Peter (the lesser)

 

Outstanding tip!

 

Before you do all this flush work try dumb old billybob's method. Here is the theroy. If you have air in the system you have moisture. pressure in the system under function causes icing and blockage in the expansion valve and no worky A/c. So unless you are getting guage readings that say you areblocked I would try this first. Remove the reciever dryer. Back it in your wifes oven at 250 degrees for 1hr. Reinstall and make sure you vacuum out the system before you recharge it. This works most of the time and is very easy. It works especially well with Ferraris because they do not make good A/C systems and they are always lossing freon. So techs just recharge without vacuming out the system to remove all moisture. O.K. I have just gone against all the experts but my method is quick and easy...try it. I rarely ever have to solvent flush.

 

That is so cool!

 

Thank you to ferrarioldman for the tip...............I printed off his reply and faxed it to my A/C shop where I just had my 1990 TR repaired with a couple of the reverse flushes and a new receiver drier.....it's nice to have "cold" A/C again !!!

$400 parts and labor (inc. receiver drier) versus removing the dash to change the valve.....big $$$$.

This website is well worth the price of a ROSSA subscription.

 

Anyone know how much oil is flushed out of the evaporator using this method? Do you guys add oil back to the system after doing this flush?

 

FWIW when I flushed my 82 308GTSi AC system, I went all out. Disassembled and flushed lines, condenser, evaporator. Changed expansion valve, receiver drier and compressor oil along with all o rings. I also changed from r12 to r134a. Vent temp is 40f room temp is 90f. I also modified the vent to flow more air. Very happy now.

 

Yeah, i'm thinking about doing a full flush and oil change as well. Will take a lot of effort, but I think it would be worth it to know it was done properly. I think the source of my problem is the shop that did my compressor change two years ago skipped stuff. They didn't change the dehydrator filter and probably didn't bother flushing the system.

 

Waymar, did you need to purge the system with nitrogen after using the AC flush solvent? Or is pulling a vacuum good enough as long as you use a solvent that evaporates completely?

 

Great info, for a common problem.