Evaporator Core

[67CHIP72]

Is there any way to test and see if the AC Evap Core is still good without the system being hooked up?

[tommie]

one off the things that I was shown when i first started turning wrenches was......

we had old lines to hook up to evap cores that were bent over and sealed. there was a pressure fitting (low side) on one of these lines and we would apply shop air with a guage usually about 100 psi, then we would set the evap core in a large mop bucket of water and watch for bubbles. this would help you find most leaks, and is the only way that i know to "bench test" an evap core....

PM me if i confused you or if you need more info

[killer71]

What do ya mean if it's still good? You can blow shop air through it to check for obstruction or obvious leaks or you can simply pull a vaccum on the entire system and if your system is able to hold that vaccum then it's probably o.k. It would be a good idea to replace the o rings if you have the system down.

[tommie]

the a c system operates under pressure not vacuum. you can pull a vacuum on any system and see if it leaks, but just because it holds a vacuum does not mean that it will not leak under pressure. Applying shop pressure to a sealed evap core and dunking it under water is a much better way to check for a leaking evap core in conditions that more closely resemble the operating conditions of that evap core. the evap core should have a pressure of around 25-50 psi during normal ac operation, and then have a pressure of 70-125 when it is not in operation. It is very hard to see if an evap core is leaking, most ac repair techs just want to replace them if in question, because the evap core is normally found to be a leaking component in an ac system. I have checked them both ways, by pulling a vacuum on the system, and by pressure dunking the evap core, I have still had some that leaked after passing both of these tests. The only true way to tell if an evap core is leaking is to have the system operational, and then add ac dye to the system, run it untill it leaks down again, or a few weeks, and then recheck for leaks using a dye light. where ever the ac is leaking oil the dye will show up using the dye light and you can tell for sure where your ac leak is coming from.

[92470]

I just replaced mine in my 71' Cheyenne this week. It wasn't cooling as it should, couldn't find the leak, so we added dye. After a matter of days, I noticed a pool of red oil beneath the evaporator core case on my fender well. Cracked open the evaporator core case, and the bottom of the original evaporator core was covered in red dye. Also found a ton of leaves inside the case which I'm sure wasn't helping matters.

I bought a new one from Chevy Duty here in KC. I paid $179.00 for it, which was the cheapest price I found anywhere. I still run R12 in mine, so not finding and fixing a leak quickly, is expensive! But when it works, it's freezing cold. My suggestion is to add some dye and keep your eyes open. Good luck.