BobQ

Change Evaporator without tearing the dash apart
2003 Lexus RX-300 Yes this is doable. BUT…
Two big problems: the 2 bolts on the Expansion valve to the Evap and the heater core tubes.
The Story: My evaporator had a slow leak, down to 4 weeks. Time to fix. I saw a youtube of how to do it right by taking out the dash and digging into the firewall. That works but it is a lot of effort. I also saw a short video where the evaporator was sliding out the right side past the heater tubes. And the blower had been removed. That video was short but showed enough to get started.
I figured I’d start by unbolting the driver seat, moving it back and seeing if I could get to the left side of the evap and remove the two bolts that hold the expansion valve to the evap. I thought it would be easy. Twas not. The insulation was easily removed and lying on my back I could get a 4mm allen wrench (not torx) in the bolts. Problem was these steel bolts were corroded in the aluminum evap. I could loosen both but they did not want to come out. And they are close together. I cut the head off one with a dremmel tool. That allowed me to get vise grips on the second and slowly got that out. Flat screw driver showed the evap was loose. I replaced the two bolts and used lots of grease in the holes when the new evap went in.

OK now to the right side. Unbolt the right seat and move rearward. Remove the right plastic panels and glove compartment. Out with the cd player. Out with the blower. Take 2 servos off the right side and the plastic cover of the HVAC unit.
On to the heater core tubes. They are in the way of the evap sliding out. If they can be cut or disconnected from the heater core they are easily flexed enough to slide the evap out. Solution: when you buy the new evap, also buy a heater core. The heater core comes with the tubes attached. Use a pair of needle nose pliers and unbend the crimps that hold the tubes in the heater core. This is much easier sitting in a comfortable chair and good lighting than when working under the dash. Object is to get the tubes out of the new core without damaging the core. The tubes are wasted. Now that you have experience in a comfortable environment you can get under the dash and removed the tubes from the old heater core being careful to not damage the tubes. Damage the old heater cor at will. The old heater core is expendable and you will likely damage the core while getting the tubes out. With the tubes out, replace the htr core.and the evaporator (use the o-rings from the new tubes on the old tubes). Carefully re-crimp the old tubes into the heater. If you have a radiator pressure tester, this would be a good time to try it.

Mistake I made: I plugged in 2 of the servos with the ends swapped. HVAC showed error code and flummoxed me for awhile. Looking at my photos I found the error and fixed the cables. But the error would not go away. Servos refused to work. Solution: disconnect the battery for 20 minutes (or less) and the HVAC computer reset and all was well.

Everything else is typical AC work. Costs: the evap and heater core were $45 and $60 on ebay. The $60 cost of the heater core was easily offset by the labor saved. You could try reusing the heater core but if you fail and need to replace it the cost from a local vendor is likely $250ish.
Good luck.

salimshah

Excellent work.

Please go the DIY sticky thread and put a link to this thread.

Salim

rmk9785e

Is video or was it a different one?