vimtutor

video: https://youtu.be/WBlgVWGNmYQ

Hi, i'm new to the LS400. I have a 1998 with an intermittent radio problem. The FM radio will cut sound violently. Only the FM setting seems to be affected. I don't usually use CD's but I did try some a few weeks ago and it never cut out, but that could have been luck.

The "ST" stereo icon on the radio will turn off when it cuts out. Here is the page from the owners manual on the ST icon (since I didn't know exactly what it was for):

https://i.imgur.com/DwGsQXO.jpg

Bumps in the road seemingly have no effect on whether or not happens. It will cut out a lot when the engine is not even turned on with nobody in the car, and will sometimes work for 10+ minutes at a time under the same circumstances.

It sounds like a loose cable somewhere but i'd rather not hunt for it in a system I am not familiar with.

Any ideas?

Yamae

I don't think it's a loose cable issue because the "ST" icon is set internally when a stereo sub carrier 19KHz is detected by a FM de-multiplexer in the FM tuner block. Also the noise when it happens tells that it's not caused by the RF circuits. In order to find out what is causing the problem quicker, I would use equipments such as a signal generator and an oscilloscope. The important first step is to find out the point where the signal is discontinued.

vimtutor

so probably just get a new headunit then.

YODAONE

Verify the condition of the battery , battery terminal clamps, battery cables, negative ground points and alternator.

Was test driving a friends 1998 LS400 and the alternator was failing due to P.S. resorvoir hose leakage.(replaced it with 2001 LS430 alternator)

The battery was also marginal.

In the procedural progression, first thing to shut down was the radio...

Usually electronics just fail.

vimtutor

I do have a P/S leak. The only other electronic issue I have is that the moonroof will sometimes try to close but then re-open itself. Could be alternator, thanks for the tip.