Blower Motor Relay????
 

Hello all,

I have an odd situation going on with very cold days, say below 15 degrees or so. The blower motor for my heat/AC does not come on. I push the temp controls and what not but I get no air movement. The heater core heats up and while driving I get some heat due to air coming in through the various vents. Sometimes the blower cycles on and off and when this happens the recirc. button comes on and stays on as well. When the temp. is warmer I have no problems what so ever except in the summer when the AC kicks on and off but does not affect the blower. Any advice or maybe just info on what is actually happening will be greatly appreciated.

Ben
'86 300 SDL
186,432 mi.:confused:

The SDL doesn't have a relay.

It has a "blower controller", a very costly part that regulates the blower speeds. If the blower functions with 12V applied directly, the problem is either the CCU or the controller.

However, intermittent blower operation can also be attributed to a worn ignition switch............the symptoms are similar. If you get high blower speed on occasion............and then nothing...........I'd work with the switch to see if you can affect the blower operation...........and then you'll know it's the culprit.

I'm far from a 126 guru, but if it's similar to the 124 the blower won't function until the CCU senses heat, perhaps the CCU is not getting a correct coolant temperature signal? Again drawing from the 124 system, pushing the DEFROST button will bypass this sensor and run the blower when the coolant is cold, try pushing DEFROST.

When the blower doesn't start on its own, switch to defrost or the max blower setting. If that gets the blower started, it probably has bad bearings. Sometimes accompanied by chirping as it starts turning.

Sixto
87 300D

if its like the 123, most likely worn armature of the blower motor.... after I changed my blower, it has been hanky-dory....