Heater switch broken?

The front heater blower quit working the other day. None of the settings work from high to low.

• Pulled the blower motor and it works fine. Getting plenty of voltage to the plug.
• Does this point to the switch going bad? If so how do you pull the old switch out of the dash?
• Could the resistor still be bad?

It's getting warm up here in Michigan so I need to get this fixed. Any help would be appreciated.

It could certainly be the resistor (there's a fusible link in the T1N which will disable all speeds except high, i think)
If even High doesn't work... and you say there's voltage at the motor connector?
In fact, your statement "Pulled the blower motor and it works fine. Getting plenty of voltage to the plug." seems contradictory:
(a) motor works if voltage is applied
(b) there's voltage at the plug (so motor should work)
BUT: if the resistor was *mostly* broken (i.e. high resistance path exists, not low) that would show a high voltage with a voltmeter (which puts no real "load" on the circuit), but would not pass enough current to the real motor load. (it takes current AND voltage to power the motor).

So my vote is resistor (first), then switch.

Here is the T1N schematic for the blower switch and resistor (note pins are NOT in 1-2-3 order):
(the "B" in the triangle goes off to the motor... note how HIgh speed avoids the resistor.




Here's "Boatman"'s post on repairing one: (the RadioShack part number is that #270-1321 entry)



--dick

If voltage is applied directly to the motor from a battery the blower works. I had read that high speed on the fan should work even if the resistor is bad. So that made me think the switch was at fault. I will try Boatman's test to make sure. Thanks for the info.

Blow motor connector is a good known fault

johnshmit said:

Blow motor connector is a good known fault

Click to expand...

That and depending upon how the testing jumper power was applied (did you need to supply ground?) I would test that the normal system ground is good before tearing into the switch. Have fun. vic

Just looked into tearing into the switch. Looks like a nightmare. Anyone have any experience swapping one out?

Called the dealer today and they are saying that the entire panel needs to be replaced. At $560 for the panel that one heck of an expensive switch. Any suggestions where I can find a used panel?

Ohno said:

Called the dealer today and they are saying that the entire panel needs to be replaced. At $560 for the panel that one heck of an expensive switch. Any suggestions where I can find a used panel?

Click to expand...

It is a control module, not a simple switch.

They were able to diagnose that over the phone with never seeing the vehicle? Was it a fairly long personal telephone conversation with a Sprinter mechanic? One of the only guys I would trust to diagnose remotely is Doktor A because he is very knowledgeable and knows what questions to ask. I'd certainly want someone to do some real testing before replacing something like the main panel. They don't have a lot of failure history going by postings I remember here.

Have you tested for power at the resistor connector? Have you double checked all the fuses. Sometimes the fuse links separate and it is not visible without pulling the fuse. Good luck. vic

All the fuses have been double checked. The wire leading from the blower to the resistor check out fine. The next thing to check would be the back of the panel but getting access to that seems to be a bear.

The shop would be more than willing to check it out for $90.

Ohno said:

Called the dealer today and they are saying that the entire panel needs to be replaced. At $560 for the panel that one heck of an expensive switch. Any suggestions where I can find a used panel?

Click to expand...

tell the dealer to stick it.heres one.

http://www.ebay.co.uk/itm/Mercedes-...CommercialVehicleParts_SM&hash=item4ab65b4695