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How to remove evaporator on 90 silverado

webbch on Tue June 11, 2013 12:13 AM User is offlineView users profile

Year: 1990
Make: Chevy
Model: K2500
Engine Size: 5.7L
Refrigerant Type: R-12

Can't seem to figure out how to remove the evaporator on my 90 silverado to flush it. It's in the cab. I got the heater core out. The manual says to remove four screws holding the evap cover, which I did, but it doesn't want to budge, and I don't want to break the ductwork getting it out

Do I need to remove the dash to get at the evap? Manual didn't mention anything about dash removal. I'd welcome any tips from someone who's done this before. Thanks.

Smokey65662 on Tue June 11, 2013 11:44 AM User is offlineView users profile

I have a 93. Seeing as they are so similar I can tell you it is going to be a pain in the butt. You have to pull the dash out, then pull the whole evap assembly out to get at it. We got lucky as far as the heater core goes but as far as the evaporator is concerned you are going to have to pull the dash. That said, I think you could get away with not pulling it if you flushed with dry nitrogen like many shops do.

TRB on Tue June 11, 2013 2:15 PM User is offlineView users profile

Use this as a guideline. It for our kit but process should be close. Skip the steps that don;t pertain to the evap assembly.


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webbch on Wed June 12, 2013 12:15 AM User is offlineView users profile

You guys must have a lot more finesse than me. I can see how one would do it that way, but the fit is too tight for me. I think I'll pull the dash and save myself the aggravation and risk of breaking stuff. Will probably replace the evap whether it needs it or not after that amount of effort :-)

iceman2555 on Wed June 12, 2013 12:21 AM User is offlineView users profile

Why remove for does not need to be removed for this procedure if this is an OE system....replacement yes.....flushing no.

Flushing with a gas....not gonna clean the lubricant out. Need a liquid for that.....can then purge with nitrogen if you like....but to remove residual lubricant...going to need a good liquid based flush chemical.

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Toddc72 on Wed June 12, 2013 2:02 AM User is offline

I have done a 96 and now a 94 just recently. The 96 I did in the vehicle. Got it done but was a major pain. The 94 I just loosened all the dash screw and bolts and hinged the passenger dash side out and up. Took whole assembly out and did it on bench. Came out alot easier than I had imagined after being afraid when I did the 96. Plus you seal the box better to prevent leaks.

webbch on Wed July 10, 2013 6:15 PM User is offlineView users profile

Well, I went ahead and dropped the dash, which made it much easier to get to the evap. At that point, I just replaced the evaporator rather than risk it going out at a later date.

I now have a new compressor, condenser, evap, and accumulator. FSM called for 37 oz of R12, capacity listings on this site called for 44 oz, so I put in 40 oz as a happy medium. I flushed all the lines and put in a total of 8 oz mineral oil distributed to the various components. Installed larger tranny cooler, changed tranny fluid & filter, installed inline tranny filter (magnefine), replaced steering rag joint, tightened up steering gear, tightened up the steering wheel tilt mechanism, put on a new cooling fan clutch, and fixed a number of other odds and ends. Truck cools great now, and drives a lot nicer as well. It threw me a bit initially to hear the roar of the cooling fan which I never used to hear. I'm guessing that means the new cooling fan clutch was definitely warranted.

On a 30 minute commute to work at highway speeds and ambient temperatures in the low to mid 80's I'm guessing, get a good amount of "frost" on the accumulator and line running to it. I expect that's farily normal though. The A/C is back to cooling how it did over 7 years ago when it last had R12 in it (A tech installed Freeze 12 after a failure about 7 years ago, which is what prompted me to start doing my own A/C work to begin with)

Thanks again for all the great help I've received from the folks here!

Edited: Wed July 10, 2013 at 6:18 PM by webbch

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