2007 Sonata Rear Window Defroster
 

Hi!

I just purchased a used 2007 Sonata GLS, my first Hyundai. :)

I noticed that with the rear window defroster, the top five lines in the grid do not heat up, but the rest of them are fine.

I am aware that the radio antenna is in the rear glass. Is the antenna those top 5 horizontal lines (which might explain those lines not heating)? If so, I won't worry about it, but if otherwise, I'll bring it back under the warranty they gave me (probably requiring a rear window replacement).

Thank you.

Some of the lines at the top of the rear glass are the antenna but I don't recall how many. Five seems like too many but I'm not sure without checking my Sonata which is covered in snow at the moment.

I called a local Hyundai dealer today. The service tech indicated that it is a break in the grid and that the only way to fix it, is to replace the rear glass.

The dealer was able to repair the rear defroster, without having to replace the glass.

Rear Defroster and FM Radio Transmission
 

When I activate the rear defroster, I lose FM transmission on the car stereo. AM reception is fine? Any ideas?

I have the same issue of rear defroster radio noise with a 2010 Accent Hatchback. I found this post using a search, hoping for a fix.

I am assuming the defroster power circuit has a switch-mode current limiter somewhere in the DC line, similar to what LED bulbs or light fixtures use to limit the DC and prevent burning out the LEDs.

Cost-saving switch-mode regulators omit noise filters, and the connected incoming and outgoing wires act as antennas to transmit unwanted hash across multiple radio frequencies: FM, AM, fire band, police band and probably short wave, too. Strong stations override the weaker hash, but weak stations are interfered with or covered up by the noise.

Quality switch-mode regulators have filters included to trap the hash inside the filters, and only input and output DC.

My Accent does not have an in-glass antenna. It has a "rubber duck" antenna and amplifier on the roof ahead of the hatch. The antenna still picks up enough hash from the wiring to be a problem. That's the probable "why." Other than turning off the rear defroster and using the side-view mirrors, is there a fix?

What if you unplugged the alternator , to see if that hash is caused by the alt ?

Also if the antenna is being able to be partially grounded reception suffers.

Thanks for the reply.

No it is definitely not the alternator. The hash signal starts when I press the rear defroster switch on, and ends when I press the switch again for rear defroster off. Alternator 'whine' noise heard in a radio changes pitch with engine RPM. This hash does not. Also, alternator noise can get worse with changing heavy electrical loads, such as headlights, wipers, heater, and brake lights all on full while idling at a traffic light in bad weather. The hash noise has one signal strength.

The noise I hear definitely has the characteristics of an unfiltered switch-mode device. I don't know if the circuit would be located under the dash, or somewhere underneath the trim in the rear.

If I could find the device, I could possibly put a filter on the wires, but any filter must be installed close to the circuit board. Alternately, if I measure the voltage and current of the circuit output, I might be able to substitute a linear mode regulator, or even a large-wattage resistor. But I would have to find the device to disable it.

I just wondered if anyone here had already solved this issue, or if there might be a known TSB about it.

It is not unheard of for some manufacturers to knowingly use less expensive components in various mass-produced products, and reserve the 'good' components only for those who complain. I'm not saying Hyundai is like that, but it happens. Pennies turn into dollars when repeated hundreds of thousands of times.