Do I have a bad relay if my ac comes on only when i hit a bump 2010 audi a4

Asked by Jul 27, 2017 at 03:54 PM about the 2010 Audi A4

Question type: Maintenance & Repair

9 Answers


Could be anything electrical or a weak clutch magnet on your compressor. Loose connection, split wire making contact, something loose in or under fuse box. Relays do get weak and work intermittently and sometimes with a hit on them or close by. Ground wire loose? Connections to compressor all tight?

I will check all my connections Thank you


See if you have an identical relay that matches the AC relay in the box and interchange them to see if the other circuit now has issues. Many times the horn relay is the same as the AC clutch relay. MCLT is what many makers label the compressor relay.

The compressor will come on and the blower is not so then I open the hood and drop it. and the blower will work? Car has 42000 miles


Check the blower resistor on your car. Generally on passenger side in cabin by the persons feet or up a little under dash. Close to the blower that blows across evaporator. Google it for your car and location. About $30 - $40 of this is it. Also find the fuse or relay that runs this blower circuit and see if it is a bad relay, fuse or loose connection in circuit? Do a continuity test from inside cabin to fuse box location of that circuit. Also does some (not all) speeds work on this resistor? This is GENERALLY 100% proof that this resistor is bad. If this is good could be the control board on dash or wiring to this control board.


Blower motor resistor. Sorry. It is an easy replacement on most cars. If this is your issue...

Thanks I will check all connections, all speeds work fine when I take it off auto. And the Blower resistor for the Audi is $400.00 and the blower motor is $125.00 This is what has led me to believe that maybe I have a bad relay?


Bad Audi for those prices!!! On a serious note, Relays are very easy to check and are cheap online. I have even gone to a junkyard and pulled the entire box for pennies on the dollar. YouTube how to check a relay. It is easy! Pull a few (mark where they went) see if the one in question has a weaker clicking sound or has higher ohms than similiar ones. See about pin fittment is good in the box or if there are any melting or burn marks where this relay fit.

Thank you!!

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