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Eric, Automotive Repair Shop Manager
Category: Hyundai
Satisfied Customers: 32591
Experience:  20+ yrs. experience as repair shop manager and technician.
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05 sonata hooked battery up reversed. now the ac doesnt

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05 sonata hooked battery up reversed. now the ac doesnt work, keeps blowing number 5 fuse 10 amps, Can you help me find the short?
JA: Do all the fuses have the correct amperage for the circuits they're in?
Customer: yes
JA: Are you fixing your Sonata yourself? What have you tried so far?
Customer: i am fixing it myself, switched out the fuseblock and etacs module and still have the same issue, number 5 fuse on the interior fuse block, which is for the ETACS, sunroof and AC
JA: Anything else you want the mechanic to know before I connect you?
Customer: ran the car for a few minutes before realizing the battery was reversed. radio fuse blew but i switched it and it is fine.


Ok, first remove the overhead console or lamp assembly to access the sunroof motor and relay. see attached

disconnect the relay and see if fuse blows. If it doesnt, then plug relay back in and disconnect the sunroof motor. If the fuse blows, replace relay. If it doesnt, replace the motor

If still blowing when relay is disconnected, then no relation to sunroof

The fuse also handles the rearview mirror. Disconnect it while at that location. If no longer blows fuse, replace mirror assembly

If still blowing and as you have replaced the etacs, then that only leaves the climate control module as the culprit

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Eric and 6 other Hyundai Specialists are ready to help you
Customer: replied 2 months ago.
Tried your suggestions, fuse still blows. Next step?
Customer: replied 2 months ago.
If the thermostatic switch is fried will it cause a short at the fuse #5 interior fuse block?

Let me check the schematics

When you replaced the etacs, how did the wiring harness look going into the connectors, any signs of melting and exposed wiring

Customer: replied 2 months ago.
No everything looked good.

Any issues with fuses 4, 10,15,21,27 or 31?

If not, that eliminates the hot side from the ignition switch. If any of them have blown, we will need to look at the ignition switch to fuse box wire that feeds those fuses in addition to fuse 5

Customer: replied 2 months ago.
No the only other fuse that blew was the radio which I switched and it works now but don't remember which number it was


Ok, when you uplugged each of the components, which one plugged back in caused the fuse to blow - the sunroof, the rearview mirror or the climate control unit

Customer: replied 2 months ago.
I did not unplug the climate control unit, where do I unplug that?


You have to remove the climate control panel and unplug it on the rear. Use a screwdriver to pry off the center fascia trim panel and you will see the screws for the control unit. Remove them and pull out the control unit and unplug

Customer: replied 2 months ago.
Ok I'll do that and get back to you, thanks for your help with this!

you are welcome

Customer: replied 2 months ago.
It blew when I plugged in the 6 prong connector on the driver side, fan speed control.

Ok, does yours have the manual climate controls or the automatic/digital climate controls panel

Customer: replied 2 months ago.
Manual and when the switch was off fuse was ok but as soon as I turned to the 1st position it popped


Ok, we will start at the end of the circuit and work our way back to the switch. underneath the right side of the dash is the blower motor and blower motor resistor - see attached.

disconnect the blower motor, turn on the fan switch. If fuse doesnt blow, blower motor is shorted.

If fuse does blow, reconnect and then disconnect the blower motor resistor and turn on fan switch. If fuse doesnt blow, the resistor is shorted.

If the fuse does blow, then it is the fan switch itself which has shorted.

Most of the time it will be the resistor

Customer: replied 2 months ago.
Hah! Fan motor ok, disconnected the resistor, and the fuse blew when turning the switch switch no good?


correct, that means the fan switch shorted.

Customer: replied 2 months ago.
To be sure can I jump the wires on the connector ? There are 6 wires, one is a very thin brown wire possibly a ground


brown is power supply to the switch

black is ground

yellow is speed 1

tan is speed 2

light blue is speed 3

black with orange stripe is speed 4

as it is blowing on low speed, you can jump the brown to the yellow with the black grounded.

Customer: replied 2 months ago.
Ok thanks I'll check it out!

sounds good

Customer: replied 2 months ago.
Well I jumped as you said, blower does not blow BUT compressor is running, fused ok

not sure why it would kick the compressor on but not the blower. but since it did not blow the fuse, then it is the switch that is bad

Customer: replied 2 months ago.
Yeah something funky there

the first step will be to replace the switch and then test everything, but based on the tests, we know the switch is shorted and blowing the fuse

Customer: replied 2 months ago.
Ok I'll find a new switch and we'll go from there. Probably get back to you in a few days by the time I get the new switch and install it. But we are making progress! Thanks again!

you are welcome

Customer: replied 2 months ago.
Eric, I changed the switch, fuse still blows. I unplugged the fan, resistor, and the 2 connections behind the climate control panel, and the fuse still blows
Customer: replied 2 months ago.
We didn't check this, thermostatic switch?
Customer: replied 2 months ago.
I did unplug that connection at the Thermo switch still blew.
I fed the blower directly from battery and works fine. I jumped the terminals on the switch connector and still the compressor kicks on but not the fan. I did notice the compressor kicked on whether or not I grounded the black wire going to the switch.
Customer: replied 2 months ago.
I started unplugging all the connections at the interior fuse block. This is the connection that blows the fuse when I plug it in. Also if this is unplugged the motor turns over but doesn't run. I am going crazy, help!

That is really strange. Fuse 5 is on connector J not D.

Let me see if I can find what is on connector D

Customer: replied 2 months ago.
Ok thanks

Hyundai does not make this easy. Their connector pinouts only show pin number, no wire color and not what it goes to.

So far, I have found 1 wire to D connector - orange wire from ignition switch.

Still going thru all the wiring diagrams for the fuse box to find the other 3

Black wire is ground

I have gone thru every power distribution wiring diagram and those are the only 2 I have found

Customer: replied 2 months ago.
I'm thinking there is a relay shorting out but I'm pretty sure I pulled out all the relays related to the blower fan. Question: in the main power distribution box under the hood, which relays would be on the blower fan circuit?


None. blower motor relay are by the blower motor housing see attached

Fuse 23 in the engine compartment fuse box is for the blower motor relay, but you have not mentioned it blowing

Customer: replied 2 months ago.
Right fuse 23 is fine. I found one relay at the blower
Customer: replied 2 months ago.
Ahhh I unplugged it turned switch on when I plugged relay in fuse blew! You thing this is the culprit?

Either it or the wiring to it. Before trying to trace the wiring behind the dash, I would swap out the relay

Customer: replied 2 months ago.
looking for a supplier now. Thanks and I hope this works!

you are welcome.

You should be able to take it into Autozone or other major parts store and they can cross reference the number on it to theirs

Customer: replied 2 months ago.
Thank you yes I found an autozone that has it

you are welcome

Customer: replied 2 months ago.
Success my friend ! $9 relay was the culprit!

great to hear