1991 Ls400

[artwalk]

I am searching for the correct location of the radio amplifier in a late '91 LS400. I was told once that it was located under the passenger seat, but this not the case. I need to locate it to solve a problem of the radio coming on when the weather is warm/hot, thus drying out what I was advised are probably coroded terminal connections, as the radio comes on of its own accord when the sulphur build-up dries out this permitting the connection to positively make live contact to the radio. Once contact is made the radio, both AM and PM work just fine. I'm not sure where else to look for this amplifier unit. Has anyone experienced this problem. Up until now the radio and CD player have worked superbly.

[landar]

And here I always thought the amp was in the trunk, right side. But what do I know?

I would really focus on the head unit where the on/off switch is. Could be worn and needing replacement.

Here is a tutorial on removal -> http://www.lexls.com/tutorials/audio/headunit.html

[artwalk]

Thank you for that unput, but I've no doubt you know far more about Lexus than all of us put together. Your response, however, doesn't seem to address the ad hoc manner in which the radio only works during warm-to-hot weather, whereas your solution suggests the problem lies in the head unit and thus in the on/off switch. But what do I know? I'm more interested in locating the amp first and determining whether the connection points are corroded. Given that my '91 LS400 is in Australia and thus right-hand drive, would that mean that everything is opposite hand to a USA model? For example - the radio power aerial is on the passenger side of the trunk, which is the RH side looking directly at the car from the front. If I can locate the amp there as well, I may be able to solve the problem quickly and easily. If it's not fixable at the amp, then I can follow your suggestion, but not something I can do myself so remuctant to go there. It remains as to just where is the amp located?

[artwalk]

One other point I didn't mention in response to your suggestion that it may be a worn on/off switch, is the fact that I have very rarely ever used the on/off switch in the 22 years I have owned it from new, The radio etc was always left on, so it was turned on and off with the ignition. I would have thought this was pretty common?

[landar]

Brian, I must explain that I am an electronics engineer and am infected with this 'disease' of trying to get to the root cause of problems. I have found over many years that if I do not find the root cause, the problem with not go away. I remain skeptical of this "sulphur build-up" unless your battery is right next to the amplifier. I have found over the years that presuming something often leads to erroneous and frustrating troubleshooting. Test everything, assume nothing is a good motto. That is why I suggest you play with the head unit first. You do not even need to remove it. With the ignition switch on, will the radio turn on and off every time for 10 tries? 20 tries? I know it sounds silly to do that but its part of some initial simple sleuthing.

My 92 USA LS400 has the aerial on the RH side(passenger) so it is very probable that your amp is located opposite of a USA model as well (which would be on the LH side). I would do some digging in the trunk to see if you could locate the unit.

[artwalk]

Landar - Did as you suggested - with the ignition on, I turned the radio switch on and off, both 10 and 20 times and the radio reacted accordingly each time, so it appears the switch is functioning as it should. Haven't been able to get to the trunk yet, so just to clarify before I start taking the lining out - looking into the trunk, the aerial is on the left, would that dictate the location of the amp, to be on that side too? The radio has always come on with the ignition, that is how it comes on randomly when everything warms up, its been doing this for the last 3 years with a consistent pattern of ambient warmth in conjunction with (I assume) some miles.It does not do this during the winter months.

[sha4000]

I believe the amp is in the trunk behind the CD player or behind the carpet behind the gas tank. Which system do you have? Nak or pioneer?

[landar]

Your aerial is on the same side as my 92. That is the LH side as viewed from the back (yours being the passenger and mine being the drivers side). I would suspect that your CD changer and amp are on the RH side as well (drivers) just as a US model. Lexus did not have to mirror everything for RH drive models, just the steering wheel, pedals and instruments. Find the CD changer and I think you have your amp. Hope this helps.