AC Evaporator core replacement on 92 400E - Page 3 - PeachParts Mercedes-Benz Forum

aldedmon · #1 07-08-2003, 12:14 AM

I want to thank the well wishers before during and after the job. It was rally a labour of love. I encourage any/all of us who needs this job done, and you have the space / time........ to DIY. get the parts fron Phil...(He's the man).Absolutely NO special tools required. I have a prety good set of craftsman and a cheapo $20 set of "Companion"(Sears bottom of the line Taiwan) tools. Which includes 1/4 and 3/8 drive ratchets/ SAE& metric sockets and wrenches 1/4-9/16 and 7-15 , phillips/flat screwdrivers . I used the COMPANIONS and they were all I needed!!!! So surely each of us has at the very minimum a COMPLETE set of cheapo tools. If you don't go out a buy yourself a BAD @$$ set with the $1000 you'll save by DIY.

miktvk · #2 07-08-2003, 10:23 AM

Thanks for the inspiration Albert!
I look with less dread on this task.

The 95 wagon is now on 116,000, with nothing having gone wrong yet. But...I feel like there is a really large ticking clock hovering over me these days. So far no major problems.

Once, a while ago, I had to replace a heater core on a '65 Riveria I owned and restored...I won't say more, except that it is a very similar project, but with all metal parts everywhere, no plastic! Oh man, was that painful. And yes of course, didn't I have to do it in the middle of August.

Someone in the Riviera owners association figured out a way to actually cut out a re-closable opening in the firewall to remove the core/evap., that's how desperate some people were getting; but I didn't do that, afraid to make a bad situation worse.

ke6dcj · #3 07-08-2003, 11:54 AM

I had the dash apart to replace all the HVAC vaccuum elements, however, there was no leak in the 1988 wagon's evaporator!

So I'll just wait for the leak.

BTW: since the evaporator and condenser for a R12 and R134a W124 use the same replacement parts, given that I've replaced these parts and have converted to R134a, do I fill to the specs of the W124 R134a label or is it still 80% of the W124 R12 label?

Also, I'm thinking about going back to R12 since I'm moving to Florida. Is it worth it? Can it be done WITHOUT a new compressor

I'd replace receiver/dryer, pressure switch, and expansion valve, flush the system, drain the compressor of PAG46 oil, and hold a vaccuum for 1-2 days, and change out the O-rings back to R12.

aldedmon · #4 07-08-2003, 11:58 AM

Hello Neil, This is a deep thread and should be entered as a new thread all on its own. Larry Bible , Steve or Donnie would better be able to answer it. I agree with your thinking/logic, but this is best answered by the experts

#5 07-08-2003, 12:12 PM

Albert,

Not only do I congratulate you on a job well done but thank you for posting the blow by blows here on the site to share with us.

Actually, the truth be known, I think you're just a wimp when it comes to the mild Houston summers so you had to get it done quick.

Seriously, I've spent enough time in Houston in the summer to understand the need for the a/c. I lived in dry Lubbock as a teenager and when we came to Dallas in the summer it just killed us because of the humidity. You go from Dallas, with moderate humidity, to Houston and there's that much MORE difference. The heat and humidity is absolutely brutal.

I know what you mean about the feeling of accomplishment after you've done something like this. After you've been there and done that then you know that you can repeat the job and its great to have that confidence.

That said, my 124 evaporator is still holding tight. MAYBE I'll dodge the bullet altogether. If it starts leaking though, I'll just drop it by your place and use the 500E 'til you're done.

Hope to see you again soon,

#6 07-08-2003, 12:21 PM

ke6dcj,

If I were you I would go back to R12. BTW, yes 80 to 85% of the R12 quantity is what you need in 134 if you stay with it.

To go back to 12, you need to flush EVERYTHING to remove the oil, remove compressor and flush the PAG out of it using mineral oil, don't use solvent in compressor, put compressor back in place, put in the correct amount of mineral oil, evacuate and charge with R12. Also replace any switches or devices that you changed due to 134 pressure differences with appropriate parts for R12. Make sure you get ALL the flushing agent out of the system. This can be difficult in the evaporator and condensor, particularly the condensor.

Also, in hot weather, a 24 hour evacuation is not necessary. The hotter the components, the quicker the moisture will boil out under vaccum.

Best of luck,

aldedmon · #7 07-08-2003, 12:44 PM

Thanks Larry for the kudos. And thanks also for answering Neils question so quickly. That why I love this board. There's always a friend not far away with the answers you need to the questions that you have.

ke6dcj · #8 07-08-2003, 01:00 PM

Larry- why can't I just use the specs on the W124's R134a sticker? I did install a R134a condenser, and a R134a compressor, but still have the original R12 evaporator.

Thanks for the flushing tips if I go back to R12.

:-) neil
1988 360TE AMG
1993 500E

Zeus · #9 07-08-2003, 02:22 PM

Hey Albert!

Congrats!! That cold air rushing in must seem twice as sweet...

I'm still unsure about tackling mine this summer - time is my enemy, but I have more confidence about it now. Thanks for all the advice.

Chris

J.HIDALGO · #10 07-08-2003, 03:30 PM

I converted my car to r134 and it cools great when moving but, in stop and go traffic is not as cool. However, I don't remember too much of a difference with R12. As you know, the 124's A/C is not its greatest asset...
I just helped Neumann replace his evaporator, I think you already got in touch with him, but his newer system already has r134 from the factory. He has a 94 E320.
BTW, when are you moving to the area? Did everything work out for you?
See you!

#11 07-08-2003, 03:50 PM

ke6dcj,

Yes, since you've changed the components this would be close. Usually in a converted system you have to get close and then experiment with charge while CLOSELY watching high side pressure. It can get away from you so be careful when adding charge. Add a very little at a time then let system fully stabilize before deciding whether or not to add more. Watch vent temps closely as well.

Good luck,

ke6dcj · #12 07-08-2003, 06:48 PM

Thanks Larry. What pressures on the HIGH and LOW side should I have with R134a when everything is stabilized?

Also, what should the vent temp be?

:-) neil
1988 360TE AMG
1993 500E

#13 07-09-2003, 08:22 AM

This is one of the problems with converting to 134, excessive high side pressure. On converted systems the high side pressure can sometimes go up to 300 PSI. The important thing is that you don't get into a situation where the pressure runs away. The high side pressure should stablize once the vent temp is stabilized. There are no hard and fast pressur or temp readings to look for. If you are getting a stable 40 degree vent temp and the high side does not continue to increase after stabilized, you are probably okay. Proceed cautiously when adding 134. This is another reason for staying with R12 in an R12 system.

Good luck,

aldedmon · #14 07-10-2003, 11:34 AM

Larry,
The A/C is cold, but when I press the HIGH button, it doesn't blow strong like before. When I press the AUTO button, it too does not Blow strong like before and the LOW button barely blows at all.
I start the car and press HIGH and gradually over the next mile it begins to blow higher and higher till it hits a its new High speed which is considerably less that the original High speed was. HELP!!!

#15 07-10-2003, 11:46 AM

Albert,

The only comment that I know to offer is that, when I have seen the ACC go all over the place like this, I've seen the fan that draws sample air through the grill near the rear view mirror not working.

This small fan is in a few different locations on the various model 124's. Mine is near the glove box.

You could check it by holding a cigarette(yuk) or some other source of smoke near that little grill and see if it draws the smoke. If working properly, that fan draws air through the grill any time that the ignition switch is on.

Hope this helps and best of luck,