No AM radio signal on two aftermarket HUs?

[redbluff]

Originally Posted by jbll

I have the exact issue with my HB and Alpine Head Unit with FM reception
didn't try AM...

What do the power antenna change to the FM reception?

And btw, my reception was VERY good with my Toyota Heand Unit...

I tought the power antenna cable was for the antennas which go up and go down all alone....

The antenna is amplified to boost the signal. I only guess that we dont have the non stock units connected up right.

[jbll]

Originally Posted by redbluff

The antenna is amplified to boost the signal. I only guess that we dont have the non stock units connected up right.

so, if i change the wire, I will get a better reception???

[atebit]

Yes, powering the in-glass antenna now provides me with AM reception (as opposed to no AM reception) & improved FM reception!

[barryware]

Does anybody know how much current the antenna amplifier draws? The wire for a power antenna (motorized) or an external amplifier (on/off) on my head unit states 300mV max.

I have AM reception but it sucks. I too have made the mistake of not supplying power to the antenna amplifier.

[enkid]

I think the scoche adapter power antenna lead is blue....it might be blue with a white stripe

I *think* the antenna amplifier draws about an amp, but I'm not sure. I didn't measure it.

I do know that Yaris sedan's glass antenna is one of the best in the industry, beating antennas in cars most of us could only dream of owning...

[barryware]

Originally Posted by enkid

I *think* the antenna amplifier draws about an amp, but I'm not sure. I didn't measure it.

I just connected the amplifier lead to the accessory power wire. Done! perfect!

Reception is great now.

[edwardthed]

Barryware,

which wire did you connect to for the power antenna for the AM signal?

[barryware]

Originally Posted by edwardthed

Barryware,

which wire did you connect to for the power antenna for the AM signal?

it has been so long, I don't remember. I use the complete service manual download from a link on this forum to find the wire that is in the radio harness plug.. Not sure, but I remember it as being blue.

Using the harness I bought for my head unit.. I connected the wire to power the rf amp to the switched 12v wire to the head unit.

So.. when ever I turn on the ignition, the rf amp powers up.

[tomkecil]

Originally Posted by barryware

it has been so long, I don't remember. I use the complete service manual download from a link on this forum to find the wire that is in the radio harness plug.. Not sure, but I remember it as being blue.

Using the harness I bought for my head unit.. I connected the wire to power the rf amp to the switched 12v wire to the head unit.

So.. when ever I turn on the ignition, the rf amp powers up.

I stumbled on this after Googling took me to lots of places. I had the same problem - AM dropping in and out and FM not nearly as good as it was with the original head unit. Both are now excellent on my 2007 Yaris sedan. If you're just finding this from a search here's the full picture:

removing old head unit
It took <1min to pop off the four fascia panels around the unit and undo the four screws that hold the deck in place. Easiest car I've installed on!

Mounting new head unit
I bought a single din Kenwood and a single din tray that's especially made for Toyotas and comes with the two black plastic 'filllers' that are the right size to fill the gap in the dash. The tray and fillers were $20 and fit perfectly - see picture

Connecting the cables
I bought a head unit wiring harness for later model Toyotas on eBay (~$12) and then soldered and heatshrinked the leads onto the other end of the harness that came with the Kenwood. As the harness was designed for ISO connections all the colours were a straight match to the Kenwood harness, so it was simple. I plugged it in and it all worked well except for the radio reception.

Fixing the radio reception
Thanks to the posts above and another search, I confirmed that the Yaris is fitted with a signal amplifier that sits in between the rear window antenna and the aerial lead in the dash. It received power from the old head unit via a lead in the factory harness that runs to the amp down the back of the car, but the new unit was not giving it power. The lead you're looking for is the all black one in the middle of the Yaris's blue plug. When you get 12V to it the reception returns to the great quality of the original head unit. The ISO Toyota harness pin that connects to that black lead is blue, and the Kenwood had a blue lead designed to switch those motorised antennas on when the head unit is on, so, connect blue to blue and the job's done.

I now have streaming bluetooth audio, good quality hands free phone calls (I mounted the supplied external microphone at the top of the trim on the driver's A pillar) and most importantly, a happy wife.