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Evaporator Age: A Replacement Criterion?

Wobbly007 on Wed July 24, 2013 9:22 AM User is offline

Year: 1986
Make: Vixen
Model: 21TD
Engine Size: 2.8
Refrigerant Type: R-134a
Country of Origin: United States

My 21 foot mini-RV is rear-engined with compressor and condenser in rear, mid-ship evaporator with TXV, and front GM evaporator with orifice tube. I converted it several years ago to R-134a. The original BMW (Denso?) compressor has been replaced with a Sanden. The condenser has been replaced with parallel flow unit. There's a slow leak which I haven't been able to find. I'm wondering if the 27 year old evaporator should be replaced because of its age.

I was going to replace the all the hoses, but read that non-barrier hoses are now not routinely replaced. The lines from front to rear are steel.
They have some surface rust, but would be difficult to replace.

webbch on Wed July 24, 2013 6:23 PM User is offlineView users profile

Finding leaks can be tough sometimes. Is there dye in the system to help aid in finding the leak? Are you using an electronic detector?

How's the cooling after a recharge? Here is an interesting read on general motorhome A/C issues/problem areas if you haven't already seen it.

Wobbly007 on Wed July 24, 2013 8:35 PM User is offline

I'm waiting for an UV flashlight to check for dye. I have a Yokogawa detector.
I also have a small nitrogen bottle and a R-22 cylinder, so I could test a blend.
I'm just thinking that at 27 years old, it may be time to replace the evaporator even if it isn't leaking.
Thanks for the link.

Dougflas on Thu July 25, 2013 7:46 AM User is offline

DO NOT USE R22 AS A TRACE GAS IN A SYSTEM WITH RUBBER HOSES. R22 will permiate the hoses and send you chasing your tail.

Wobbly007 on Thu July 25, 2013 9:04 AM User is offline

No experience myself, but this article claims that R-22 added to nitrogen is excellent for leak testing on R-134a systems:
Trouble finding A/C leaks? (especially with 134a)

webbch on Thu July 25, 2013 12:54 PM User is offlineView users profile

If the time/hassle required to test the evap exceeds the $$ to replace, nothing wrong with replacing it IMO. Be aware that if you used brake cleaner or similar to clean some connections that it will set off the leak detector for at least several days. I recently chased my tail on that one for awhile with my Tek-Mate.

Since you need R-134a to charge anyway, why not use it as the trace gas as well? It's cheap enough. Don't really understand why you'd use the R-22 (no other use for it perhaps?).

Wobbly007 on Thu July 25, 2013 7:19 PM User is offline

The article claims that R-22 is easier to detect than R-134a, and it disrupts the surface tension of residues which temporarily seal leakage paths. Pressurizing to 200 psi with nitrogen and 4 oz. of R-22 is what the author claims to have successfully used in 40,000 vehicles.

Edited: Thu July 25, 2013 at 7:20 PM by Wobbly007

webbch on Thu July 25, 2013 9:04 PM User is offlineView users profile

How much have you used your detector? With my tek-mate detector, if anything, it's OVERLY sensitive. I tend to keep it on the low sensitivity setting to minimize false detections, and only use the high setting to hone in on a suspected leak. No trouble picking up 134a, that's for sure. Have you had an issue with the sensitivity to 134a on the Yokogawa (never used that one)?

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