W108 Heater Blower Hack Questions

[1971.280SE]

First, a brief introduction. The family car when I learned to drive as a teen in the mid-70's was a '67 250s 4-door with a 4-speed manual on the floor. Loved that car, and recently jumped at the chance to buy a '71 280se 4-door with that same, rare 4-speed manual on the floor -- the first Mercedes in my family since my folks sold the 250s in 1980.

I'm now in the process of replacing all of the major safety items, e.g., soft fuel lines, brakes, flex-disc, sub-frame mounts, etc. I'm also facing the dreaded job of a heater blower replacement (at least the previous owner took $1500 off his asking price in light of this task).

Having read here and other MB sites extensively, I'm planning on the Niedermeyer hack involving cutting an access panel from above and using a motor and fan wheel from a '76 Ford Courier. But the only Courier motor readily available new at parts suppliers is a unit for Couriers with AC -- 4-Seasons #35590. It doesn't look like the kind of motor described in the hack because it is double-shafted and lacks a mounting flange.

This 4-Seasons motor fits a lot of vehicles, so I checked some of those to try to find a motor that seemed more in line with the hack. To make a long story short, I found a motor used in a variety of Fords, 4-Seasons #35572, which looks like it might work with the hack along with a widely used fan wheel, 4-Seasons #35602. Photos and specs for these items can be found by plugging in the part numbers here: http://www.4s.com/Online%20Catalogs-eCatalog/Content.aspx.

Here are my questions for those of you with some experience with this hack:

• Do this fan and wheel look like they would work?
• Is there another readily available substitute that would definitely work?
• Are there any other issues in this hack that someone preparing to do it should know about?

Thanks in advance for any help.

Bill in Maryland

[twinockchef]

Have you not considered just replacing the motor with a new one? You do not have to be a master mechanic to change it. You only have to be patient.
A $1500 reduction is a great deal. If you did it yourself the only cost will be a new blower ($350).

Below is a fairly accurate procedure for the job.
Take the heater core to a radiator shop and have them preform a leak test. Make sure it is prefect. Better safe than sorry.

The last time I did this it only took me about five hours. You will need to take your time with the process of removal and installation. Many of the parts may break. First order a new heater blower fan and rubber seals for the heater core valves.
1. remove the vent on the dash - two screws
2. remove the left and right covers, which cover the frame between the windshield and door - just pull them out
3. remove the wood dash bow - two screws in the middle under the vent on the dash (be careful not to break it.
4. remove the dash cap - four screws which are close to the defroster vents and then pull the cap off ( it is attached at the front with clips.
5. remove the main a/c vent - unplug the electrical connection on the right side. There are about six screw on the underside it. It should pull right off from the clips which attach it to the dash.
6. remove the a/c blower - two screws on each side
7. remove the evaporator - three bolts, one on the left side against the firewall. The other two are on the inside of the compartment behind the right wheel were the antenna is. Unscrew the a/c lines under the hood. it takes a lot of effort too get it out.
*The lower heater vents will need to come out. To get to them the center carpet has to come out.
8. Remove the center consul - three screws, two in the middle and one at the front also disconnect the window switches.
9.remove the center carpet and the carpet on the left and right side.
10. unscrew the vents which are of the floor - two screws each.
11. remove the vents which connect to the bottom of the heater box - one screw each.
12. remove the glove box door.
13. remove the glove box interior - two screws and about seven clips. Unclip the light and then pull out the interior box.
14. remove the ash tray front
15. unscrew the four screws which hold the ash tray holder. One of which is the switch four the glove box light.
16. remove the radio
17. pull out the instrument cluster - there is a plastic nut which holds the cluster in. To get to it you will need to reach up from under the dash (this is easier said than done). With the nut off carefully pull the cluster out. Disconnect the speedometer cable, oil pressure line, electrical plug and the shifter indicator (this disconnects close to the steering column under the dash. Move the shifter and you should see the linkage move back and forth). the temperature cable cannot be disconnected. I just rotated the cluster and taped it to the left side of the dash. *be careful not to scratch the wood on the dash with the back of the cluster.*
18. remove the heater controls (this is a pain in the ass). There are two 10mm nuts on each side which hold the heater control face plate on. Unclip each cable connection (label them), two of which require a screw drive from the top (through the controls) and the bottom. Don't lose the clips. They like to pop out and vanish into the black hole of the dash. There are also two electrical plugs on each side of the controls.
19. remove the a/c hose - this hose runs from the far left vent down to the left side of the main a/c vent. It is the hose which right behind the instrument cluster. Be careful it likes to break.
20. remove the three defroster vents - the left and right ones are secured with clips which are on top of the dash. Unscrew from the dash and then remove clips from the vent. The right vent will fall out but the left vent will just moved to the side (watch for the small hose at the left of it.). The center vent is removed by a single screw at the center of the dash under the dash vent.
21. drain the cooling fluid from the radiator.
22. disconnect the heater core hose connections - inside of the engine compartment on each side of engine.
23. unscrew the heater box - two 10mm nuts on each of the box at the fire wall.
24. disconnect the electrical plug from the heater box - it is right next to the valves on the right side.
25. there is a bolt which attaches the box to the dash - it is on top at the front of the box. There may also be a connection at the lower front of the box.
Now you can remove the heater box. First pull the box back to get the heater core pipes out of the holes in the firewall. Then slide the box to the right. It takes a lot of finesse. Rotating the right side up while at the same time pushing to the right (this will help in getting the heater blower fan to clear the top of the dash. Go slow and be patient. It will come out.
This list may appear overwhelming but it works. The order of operation works well too.
If I missed something let me know.
Good Luck

[Tomguy]

Have you made sure it isn't just blocked, and spun it by hand? I got lucky and that's all mine needed. I know $500 is a lot to plop down on a NOS or NEW unit but you can use this to compare the design, and make sure it will at least fit:
http://www.allpartsexpress.com/ShopByVehicle.epc?q=1971-MERCEDES--BENZ-300sel--/v8_6.3l-Climate--Control&yearid=1971&makeid=MERCEDES+BENZ%40%40MERCEDES+BENZ%40%40X&engineid=1405741%40%40300SEL+%2FV8_6.3L%40%40300SEL&catid=Climate+Control&subcatid=Heater%20Fan%20Motor&mode=PA
Image:
http://12.153.160.115/images/catalog/full/0008356502.jpg

I would PERSONALLY, if looking to do this job, look on auto parts sites for stuff that looks similar, then get one from the junkyard or a dismantler (not to use long term per se, but see if it fits).

[1971.280SE]

Thanks for these thoughtful replies. Britton, I believe I remember seeing elsewhere on this site your procedure, and from my perspective it basically answers the question "Why?" It's not so much the expense of the part as the complexity of the installation that puts me off -- not just once but possibly in the future for a part that seems prone to failure. I'll admit I'm on the edge on whether to use the hack or your procedure and will give it further thought.

Tomguy, everything is clear. I'm afraid I'm facing blower replacement. The new parts I mentioned only cost about $35, so if I go that route I'll just try them out, and I'll post anything I learn here. For anyone reading this not familiar with the hack, it's posted here: http://articles.mbz.org/hvac/mechanical/108blower/. At least it was up to yesterday -- the site appears to be down at the moment.

[jimoneill]

yo Twinockchef, you still around?

hi, I'm part way through dismantling the dash of my 72 300SEL in order to replace the dead heater fan. I have the radio, cigar lighter, glovebox, heater control assembly, AC controls and AC fan removed. However, I'm stuck trying to remove the AC air duct that runs from the evaporator to the dash vents. I see clips when I look into the lower access hole and was able to remove 2 of them, but it's still not free.

Do I need to remove the lower dash padding in order to get at this correctly? If so, I don't see how to do this easily as it's pop-riveted to the metal. I don't see any further screws to remove. I removed the ones to the left of the steering wheel and that piece will come apart, but on the right side of the wheel, I am stumped at how to do this.

I've read your writeup, but either it doesn't addess what I'm up against, or I'm not seeing what I should. From the rest of the writeup it looks do-able to me, but I'm stuck at this point (step 5 on your post)

Thanks, Jim