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Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4971
Experience:  15 years master certified 100% fix rate and have access to factory radio codes, wiring, and instructions.
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How do test the blower motor on a 1979 300sd? The blower

Customer Question

How do test the blower motor on a 1979 300sd? The blower works intermittently and rarely, and I have not been able to make a correlation as to why it works on those rare occasions. A few times it started working when I hit a traffic bump on the road. Other times it will start spontaneously. But those times are rare now.
Submitted: 2 years ago.
Category: Mercedes
Expert:  Lou P. master tech replied 2 years ago.
Hello my name is ***** ***** i will do my best to help you , i strive for EXCELLENT service and nothing less. Honestly if you tell me you hit a bump and the blower comes on that tells me the blower is at fault. The best way to test is to turn the blower on and check for power at the plugs and if there is power and ground and the blower is not on then the blower is bad. It should be located under the passenger side of the dash. I would have to double check it has been awhile since I have worked on that era of car. They are rare where I live lol. But everything so far points to the blower as when they intermittently seize a good jolt will get them going. Let me know if this helps. Thanks for requesting me ! I will do my best to help just ask me and I will ! Please take a second and click the box and rate my service GOOD OR EXCELLENT SERVICE if you feel I have been helpful and please request me in the future. If you feel I have not been helpful please DO NOT RATE BAD OR POOR AND WASTE YOUR MONEY , I will opt out to see if another expert can provide more or better assistance so you're not wasting your money!!. Thanks for choosing just answer. Lou. also , if you feel i deserve one , BONUSES are GREATLY APPRECIATED ! 😉
Keep in mind then when you rate it does not end our conversation. you can still return here to me for follow up information if needed, Lou.
Expert:  Lou P. master tech replied 2 years ago.
The first link is the blower motor fuse. It's in the engine bay all by itself in a black case. It should be. Make sure it's not broken right in the middle. They are fragile. Heat and cold after years of use make it separate.
The second link is the black blower cover that you should see under the passenger side of the dash. Remove the black cover and the blower is inside. I would replace the blower and the regulator just due to age and sometimes a regulator will fail after blower replacement. Hope this information helps. You have to copy and paste the links.