JMK2005

I have a 2005 Honda Accord LX 4 door and every time the rear window defroster is turn on there is a lot of static interference over the radio on FM stations. I have a factory Honda radio with no custom connections to the sound system. I tested every defroster power line on the rear window and they all tested out okay reading voltage on each line. I replaced the antenna amplifier back on the left C-pillar but it still the same. The only way I can get the static to stop while the defrosted is on is pull the power from the antenna amplifier or pull the coax cable from the antenna amplifier, but by doing that the signal level drops significantly.

DCFIVER

What is the voltage from end to end on each and every grid line with only the defroster on? What is the voltage with both the radio and defroster on?

Is the window tinted?

JMK2005

I only measured the voltage from chassis ground to each line on the left side (driver's side). I never went from the far right to the far left side.
the windows were tinted but I removed all of it by steaming it off and used plastic putty knife to keep from damaging the defroster conductors.

Thanks

JMK2005

You bring up a good point. I never thought of a voltage drop on tha antenna amplifier. Do you know if the rear defroster is on the same circuit as the antenna amplifier?

DCFIVER

It is.

Too me, the tell tale pointing at the grid is when you say you unplug the amplifier,you dont get any static. Test the grid lines for voltage all the way across.In each section(left,right,middle)

A service manual or short term sub to Alldata will help you out tremendously here.

JMK2005

I measured the voltage from each power terminal to chassis ground at the antenna amplifier. I'm reading 11.8 volts DC on the white power terminal at the antenna amplifier when the radio is on and 0 volts on the brown terminal. Again when only the radio is on.
When I turn on the rear window defogger I am still reading 11.8 volts DC from the white power terminal to chassis ground.
but from the brown power terminal to chassis ground I am now reading 12.0 volts DC.
when the rear window defogger is turn off the voltage from the brown terminal drops back down to 0 volts.

Doodasi

you do not have a voltage issue. You have an rf noise issue. Your rear defroster is throwing out disruptive radio frequencies. Play a cd until your window defrosts, or get a new resistor for you rear defroster. That will probably fix it.

JMK2005

I'm not so sure I completely understand about the resistor that you mention on the rear window defogger circuit. Where is this resistor physical located so I can test it? Do you have an electrical diagram for the rear window defogger and the antenna amplifier?

Thanks

Doodasi

rear window defogger noise condenser? That might be what they call it. Different cars are set up different. Called different things. I do not have a diagram. You can google it though, and maybe find one. Never dealt with one in a honda, but i have replaced resistors/drivers in other cars. Some get really smoked. Some have the antenna in the same unit. You can also use an inexpensive portable AM radio tuned "off-station". It will make all types of unpleasant noises when brought near a source of RFI.