Another A/C Thread... Flushing Evaporators, how I do it....

[1 Wild R/T]

So, there are a few A/C threads running currently that I considered adding this to.. But they are mainly about new aftermarket systems which this isn't really needed for... This is more about trying to convert old R12 systems to R134... Back in the day there were chemicals available (mainly R141) that worked really well, just put it in the flush gun & blast away... Thanks to the EPA those days are gone, to do an effective job you have to use a few extra tricks...

So, first, since very few people own a A/C system flushing tool these days... Auto Zone has one in their loaner tool program... You give them $75 & they give you the tool... Return the tool in a timely manner & you get your $75 back... They don't typically sell the flushing solvent so they aren't making a dime... Thanks Auto Zone...



This time I ordered the flush solvent through Amazon... $14...


So, you have the tool & the solvent... But the tool isn't very effective cause the solvent is more like light oil or paint thinner than a hot solvent...

So you want to pulse the flush rather than just pushing it through the evaporator/condenser...

I add a ball valve to the discharge side of the component I'm flushing, that allows me to pressurize the component being flushed by opening both the inlet ball valve the the gun trigger with the rubber nozzle firmly sealed to the inlet port... I let the pressure push the solvent into the component & fully pressurize the component withe the discharge valve closed... Then I open the discharge forcing a rapid blast of solvent & air... I open & close the discharge valve a few times, causing solvent to blast through the component... Then I reverse the connections & flush the other way... And finally back the same way... By the time you've flushed three-four times the solvent is coming out very clean..

Discharge valve

Inlet gun

 

[Lefty71]

I use a similar flush can for HVAC. The solvent sold for it is proprietary and quite expensive in small doses. I found out that its pretty much just Acetone. You can buy Acetone in gallons for cheap in the paint dept of any hardware store or home center. Like you said, i pulse and send it through in small doses multiple times. I never had a compressor failure or any problem with a conversion (to 410a) since.
Important to note tho; flushing evaporators is only really effective with the metering device (txv) removed, for anyone that may not know.

 

[ckessel]

Makes sense to remove the orifice tube. Has small screens on it.

 

[1 Wild R/T]

Makes sense to remove the orifice tube. Has small screens on it.

These systems don't use an orifice tube... They have an expansion valve... But yeah you can flush evaporators, condensers, hoses & manifolds... Expansion valves tend to close when outside the system so you can pop the filter screen & blow out any excess oil or debris... But most times I replace the valve with one calibrated for R134... The Receiver/Dryer definitely gets replaced.. And you can't flush the compressor, all you can do is drain it... But when I'm doing these conversions I replace the RV-2 with a new Sanden... So new compressor, receiver/dryer, expansion valve & reworks hoses... On this car I'm also changing out the condenser to a triple pass design...

 

[ckessel]

Wasn't sure if the replacement systems used the tube. I know oe's, especially Mopar, used them. Sold several when working parts back in the day.

 

[Billccm]

My store keeps this in stock



https://www.autozone.com/a-c-chargi...flush-clean-32oz/210230_0_0?vehicleId=1516603

 

[1 Wild R/T]

The OE's started using cycling clutch/orifice tube systems in the 80's.... It's cheaper & more fuel efficient... But not nearly as good at keeping the air cold... But since R12 has gone the way of the DoDo bird.... And POA/STV/EPR/VIR systems are all designed to work with the pressures R12 generate..

Adapting to R134 is what we are left with...

And actually GM & Ford were more stuck on the orifice tubes than Mopar... However, Mopar loved to stick it in a line where that whole line had to be replaced, GM & Ford mostly made the orifice serviceable...

Chrysler also likes to use expansion valves in sandwich blocks...

 

[1 Wild R/T]

My store keeps this in stock



https://www.autozone.com/a-c-chargi...flush-clean-32oz/210230_0_0?vehicleId=1516603

Yeah, but you don't live in California..

 

[bandit67]

Years ago I had a compressor with massive internal failure. Sent powdered metal thru the whole system, wipe the oil on your fingers and it looked like paint poly. Took it down to just the two coils, got a funnel and hose and poured in purple cleaner. Began blowing it out with compressed air and out came nothing but foam....lots of it. Scared the crap out of me, but then hooked a water hose and started flushing , ran it until just clear , clean water. Blew that out, put the system all back together and pumped it down for an hour, and then again later. Held a good vacuum , and cooled down perfectly. Worked great for years, till I sold it. You can use water in extreme cases, AS a good vacuum will pull out the non condensables.

 

[1 Wild R/T]

Years ago I had a compressor with massive internal failure. Sent powdered metal thru the whole system, wipe the oil on your fingers and it looked like paint poly. Took it down to just the two coils, got a funnel and hose and poured in purple cleaner. Began blowing it out with compressed air and out came nothing but foam....lots of it. Scared the crap out of me, but then hooked a water hose and started flushing , ran it until just clear , clean water. Blew that out, put the system all back together and pumped it down for an hour, and then again later. Held a good vacuum , and cooled down perfectly. Worked great for years, till I sold it. You can use water in extreme cases, AS a good vacuum will pull out the non condensables.

Not the preferred choice but yeah it would work... Systems with metal all through them are risky.. If somethings hidden & doesn't move when you flush it but dislodges later it's game over... Typically you add a filter on the suction line but with cars enthusiasts own added parts don't look "right"....