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Old 01-26-2008, 07:39 PM
Join Date: May 2006
Location: St. Louis
Posts: 38
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.

'86 300 SDL
186,432 mi.

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Old 01-26-2008, 08:08 PM
Join Date: May 2002
Location: Blue Point, NY
Posts: 25,396
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.
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Old 01-26-2008, 09:30 PM
babymog's Avatar
Loose Cannon - No Balls
Join Date: Jan 2006
Location: Northeast Indiana
Posts: 10,767
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.

Gone to the dark side

- Jeff
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Old 01-26-2008, 09:33 PM
sixto's Avatar
smoke gets in your eyes
Join Date: Jun 2000
Location: SF Bay Area
Posts: 20,801
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.

87 300D
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Old 01-26-2008, 10:21 PM
tobybul's Avatar
Registered User
Join Date: Sep 2005
Location: West Michigan
Posts: 2,076
if its like the 123, most likely worn armature of the blower motor.... after I changed my blower, it has been hanky-dory....

the sooner you start... the sooner you'll get done If it ain't broke, don't fix it.. Its always simpler to tell the truth...
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