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  #1  
Old 12-26-2003, 09:05 PM
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Location: Plano, TX
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124: Heater Box Removal Secrets?

Hi All -

Merry Christmas & a Happy New Year to all the Mercedes-philes out there.

I am fortunate to be on holiday until January the 5th. I am unfortunate enough to be replacing the evaporator and vacuum elements in my 1987 124 wagon during my holiday.

Just started working on it today. Things started off pretty good - about 90 minutes to pull the dash, console, instrument panel, underdash covers, etc. Then I was ready to work on the heater box. I removed the four nuts which secure it to the firewall, as indicated in the manual. I found a fifth underneath the box, just ahead of the SRS accelerometer. (A fifth nut, not a bottle of scotch, OK?) Plus a couple more small, 8mm nuts which appear to hold the box to the firewall (in the metal strip at the top, front of the assembly).

Problem is, the thing just won't budge. I mean, it is really stuck in there. I have grabbed it with both hands and pulled with everything I have - and it just laughed at me. Didn't budge a millimeter. Any suggestions on how to proceed?

It looks like the box is sealed to the firewall (around the opening from the blower fan - remember it's under the hood while the box is inside the car) with some sealant goop. Any chance this stuff is securing the box in place? If so, how do I free it up? This car has spent 17 summers sitting through Dallas heat, so everything has had a nice, long time to cure.

Anyways, rather than get frustrated, I knocked off for lunch and went to look at motorcycles to make myself feel better. Any suggestions on how to pull that box from the car are greatly appreciated.

- JimY
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  #2  
Old 12-26-2003, 10:41 PM
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Jim,
If you have followed procedure and all has been disconnected in the car and under the hood, then I will say that we have had to use prybars to release the box from the firewall on 124's. Please make sure all parts have been disconnected before using a leverage device.
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  #3  
Old 12-27-2003, 12:32 PM
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Thanks for the tip. That's what it needed. About an hour of delicate prying around the perimeter of the box to slowly free it up. Then a bit more time to work it out of the tangle of vacuum tubing and wiring looms. Definately a slow, frustrating task, but in the end not a difficult nor complex one. Again, thanks for the help.

- JimY
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  #4  
Old 12-28-2003, 11:10 PM
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Join Date: Mar 2000
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If you plan to keep the vehicle for much longer, consider this: purchase a new evaporator box (124 830 80 60?) from M-B.

It will be the modified, new style that holds the intake air filters for the blower motor. And it comes assembled, equipped with EVERYTHING, except the air temperature sensors and air filters: blower motor, blower motor regulator, all vacuum elements and hoses, new style evaporator, expansion valve and heater core are all included.

Find a dealer who will sell it to you at wholesale (some dealers do offer price reductions for those suffering from leaking evaporators).

Crunch the numbers: on a older vehicle worth keeping, using a new box can be cheaper than replacing parts piecemeal. Plus you get the benefit of the cabin air filters.
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  #5  
Old 01-01-2004, 10:58 AM
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I think one of the folks on the board looked into a new heater box while replacing his evaporator. (Aldemon, if memory serves.) His dealer wanted $2200 for the assembly. Assuming the price is correct, I don't think it makes much sense. A good evap and new vacuum elements run about $400.

It's all back in and working great. No real difficulties putting it all back together. The heater box slides right in and bolts up to the firewall easily enough. From that point you just re-assemble the interior around the heater box. The toughest thing is probably to insure all the electrical connections are back together - there's a lot of loose wires hanging around!

I'm planning to replace the compressor, manifold, condenser, etc., but just for kicks I hooked up the vacuum pump to see if it would hold vacuum. Pulled it down to 29.5" and closed the valves. It dropped to 29" in the first hour, but has been holding there for 24 hours. It would never do that with the old evap.

It took about 18 hours of labor to do the job. So it's a big task, but not an especially difficult one; most of the work is pretty straightforward. The biggest challenge is just keeping track of the huge mass of parts and fasteners to insure everything goes back into its appointed spot.

- JimY
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  #6  
Old 01-03-2004, 12:04 AM
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Location: Sacramento, CA
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I'm in the middle of pulling the dash to replace the vacuum elements in my 300E. Do you have any tips for lifting the dash out? I can't pull it back, as the two center screws run into the center console trim. I can't push it forward, since it runs into the firewall. And the center duct running from the heater box seems to keep me from lifting it straight up.

thanks,
anthony
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  #7  
Old 01-03-2004, 12:38 AM
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jimY,
Did you replace all the vacuum elements while you were in there? Awesome job. You must be fearless.
Hazen
91 300TE 4Matic
133k mi.
evap-so far so good
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  #8  
Old 01-03-2004, 10:39 AM
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Anthony - Not sure I understand your problem. The dash is bolted to the center console; you have to pull the trim, pushbutton unit, and switches. Remove the nuts; the bolts are more or less permanently attached to the dash. I removed the dash by sliding the passenger end of it rearward. It moved back enough that the center portion could be lifted up to disengage the bolts from the center console. Once it's all loose, just extract out the passenger side door.

Hazen - Yes, I can be rather fearless AKA stupid. I did replace all the vacuum elements while in there. It's wonderful having an hvac system which actually works!

I'm taking a couple weeks off from auto mechanics, then its under the hood to replace the compressor, condensor, manifold, dryer, etc. Easy job in comparison to the evap.

- JimY
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  #9  
Old 01-03-2004, 03:38 PM
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My problem is that i can't seem to get either side of the dash to move back, nor can i get the rear portion of the dash to lift up so the bolts clear the center console. I can wiggle it around a bit, so it's loose, but not enough to get it off the heater box and out of the car.
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  #10  
Old 01-03-2004, 04:16 PM
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Nevermind - I was able to get it out by unsecuring the center console and wiggling it back a little bit.

I wonder if it goes back together easier than it comes apart?
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