AM Radio Interference

[MarinJohn]

I have an 05 Prius with 6CD changer and associated radio. No electronic mods. I get very poor reception and hear motor noise thru the speakers when the AM radio is on. On these occasions, if I shift into N the interference is eliminated. I am sure I am NOT at the outskirts of reception as my neighbor's 05 Prius gets perfect reception, as well as the loaner Prii I have driven when my car is at the dealer. I have removed the antenna and replaced it with one from the local auto parts store. Same results. I have had the radio replaced twice upon which time the new radio works as it should for a short period of time before reverting back to poor reception and interference.

While I am not qualified in electronics, it seems to me as if some kind of resistor is burning out creating a direct path between the radio and the electric motor. Anyone get similar problems resolved? Any suggestions? Thanks in advance!

[eagle33199]

A couple of questions: first, does the distortion happen with FM or the CD player? Second, is there any pattern to the problem? like rapid acceleration, gliding, ICE on, ICE off, location in the city, etc?

There is no, repeate NO possible direct path from the HV system to the radio... the only paths that exist go through the inverter to the 12V system (if that was bad, you'd have a lot more problems), and through sensors to the computers to the MFD/radio... either way, there shouldn't be anything "burning out" that causes it. A guess would be that there's a loose connection somewhere between the radio and the antenna, allowing it to sorta "short out" on the car frame... That could account for the static.

Give us some more specifics, and we may be able to better diagnose potential sources for the problem.

[MarinJohn]

<div class='quotetop'>QUOTE(eagle33199 @ Aug 21 2006, 01:20 PM) [snapback]306932[/snapback]</div>

A couple of questions: first, does the distortion happen with FM or the CD player? Second, is there any pattern to the problem? like rapid acceleration, gliding, ICE on, ICE off, location in the city, etc?

There is no, repeate NO possible direct path from the HV system to the radio... the only paths that exist go through the inverter to the 12V system (if that was bad, you'd have a lot more problems), and through sensors to the computers to the MFD/radio... either way, there shouldn't be anything "burning out" that causes it. A guess would be that there's a loose connection somewhere between the radio and the antenna, allowing it to sorta "short out" on the car frame... That could account for the static.

Give us some more specifics, and we may be able to better diagnose potential sources for the problem.
[/b]

To answer your questions:

CD player works fine, but FM reception is poor, tho doesn't seem to have the engine noise.

There seems to be no pattern...it's all the time on the AM while the ICE is engaged, not when it isn't engaged

Location doesn't seem to make a difference

Anyone?

[eagle33199]

Only when the ICE is engaged? tahts a bit odd, but it does tell us that it's probably not the HV system or the electric motor thats the problem (since those can, and normally do, run at times when the ICE does not).

I'm guessing you probably won't get help here for this particular problem... it sounds really hard to diagnose. anyways, take it in to your dealer and see what they have to say (especially if you're still in your original warrenty). It'll take a good diagnostic tech to figure something like this out... just thinking through it i can't think of anything that would cause it.

maybe your car is just mad at you for using gas :-p

[ScottY]

MarinJohn, from your first post, I thought it was the same problem I have. When I have AM on, charging or discharging current from HV battery, and when reception is poor (due to location), I will hear a faint high pitch noise from the speakers. FM doesn't have this problem.

My explanation to that is when the signal to noise ratio for AM signal is low enough (bad reception areas), and the auto gain control circuit amplifies the signal mixed with noise, you will hear this faint high pitch noise created by current going thru the cable between the battery in the back and the electric motor in the front of the car. Basically, it's a shielding problem. If there's enough shielding on the cable carrying high current, you will just hear white noise on AM if reception is bad. I can reproduce this every time when I travel thru a section of road with bad AM reception (under the bridge for example). I have not had this problem on FM due to high signal to noise ratio of FM modulation.

You were saying the problem go away when you shift to N. When you shift to N, the battery is not being charged or discharged, therefore no interference. Makes total sense up to this point.

Your second post said that there's no pattern and problem is there when ICE is engaged. Now that throws me way off. It is completely different than my assumption that your problem is caused by the interference of the current going in/out of the HV battery. Can't think of anything else at this point. Sorry~

[MarinJohn]

You know, when I last posted and mentioned ICE I was mistaken. I should have said HV battery, not ICE. My bad. Thus, when you shift into N and disengage the HV motor the noise stops. I don't think it has to do with the ICE. Thanks for your replies.

[naterprius]

Toyota has in the past manufactured a few kits for AM radio interference. It's a direct plug-in to the back of the radio (pass through for the wiring harness).

I don't know if one is available for the JBL 6-CD system. Check with your dealer; ask them if they have the Audio handbook, it's kind of an obscure item to locate. If you had the base model radio, I could probably locate the part number...

Nate

[aaf709]

<div class='quotetop'>QUOTE(MarinJohn @ Aug 22 2006, 07:53 AM) [snapback]307498[/snapback]</div>

There seems to be no pattern...it's all the time on the AM while the ICE is engaged, not when it isn't engaged

Location doesn't seem to make a difference

Anyone?
[/b]

Does it happen all along the AM band?

[MarinJohn]

<div class='quotetop'>QUOTE(aaf709 @ Aug 22 2006, 09:46 AM) [snapback]307588[/snapback]</div>

Does it happen all along the AM band?
[/b]

Yes, it does. Also, while the symptoms are always present, some days they are more pronounced than others.

I'm kinda suprised others haven't chimed in with similar problems. Good for y'all.

[rkinner]

I also have a whine in the AM radio when the car is moving - from the comments so far, it looks like bad connectionsfor the ground or shielding. I have the stock radio with a single CD player and the problem doens't seem to be noticable on FM.

I do plan on installing my HF amateur radio gear in the fall (Phoenix at this time of year doesn't make outdoor installations any fun). I will post anything that I find with that installation.

Russ Kinner, WA8ZID
Surprise, AZ


<div class='quotetop'>QUOTE(MarinJohn @ Aug 22 2006, 02:16 PM) [snapback]307793[/snapback]</div>

Yes, it does. Also, while the symptoms are always present, some days they are more pronounced than others.

I'm kinda suprised others haven't chimed in with similar problems. Good for y'all.
[/b]