dmanwi

A relative recently purchased a 2008 RX350. It was in for portering and the shop noticed a short in the horn (it went off by itself). They were unable to find the source of the short but maybe a short in the heater. I went in and pulled the Lexus service history and found some other electrical issues. Maybe they aren't related though. Thoughts? How do I find the source of the electrical short? I am afraid to take it to the dealer if it takes a lot of diagnostic time. Or is this a normal amount of electrical issues and just deal with any other problems as they arise? I would appreciate any suggestions.

02/2016 ignition pickup coil, replaced shorted @2 coil pac
7/2015 3 bulbs
4/2014 3 bulbs (clearance lights, daytime running light
4/2014 bumper light, wiring problem - customer declined
3/2014 right front clearance light
11/2012 ac light flashes, ac amplifier shorted, amplifier replaced
11/2012 ce and vsc lights, P00015, replaced variable timing actuator bank1
7/2012 ac magnetic clutch relay replaced
11/2010 drivers side heater element replaced
11/2010 horn assembly, loose connection at harness
9/2010 battery coil spark plug/replace battery
6/2010 battery coil skp plug replaced battery
6/2010 distributor hdlight, signal, bulgs replaced
6/2010 horn replaced
12/2009 lower power port - blown fuse
11/2008 horn replaced, open circuit
07/2007 non-oem theft deterrent system insalled

jadu

iTrader: (42)

Does the horn come on automatically as soon as its connected and the car battery is connected? It is possible that the horn may have failed again, but shorted this time. I don't think a short in the heater relates to a shorted horn.

If the airbag is installed correctly on the steering wheel, there should not be a short there and should be working correctly when you honk.

The first place I would look is the non-oem theft deterrent system-I believe those may be connected to the horn and will set it off when the alarm goes off. GL

DennisMik

To start with, I would suggest you or someone get a voltmeter and check the voltage at the battery while the engine is running. Not only at idle, but also at 3000 rpm. The voltage reading should be around 14 volts, give or take a tenth or two. If the voltage is up at 15 volts or higher, you have a bad alternator that can be burning out the electrical components.

But back to the horn issue. I doubt that the horn itself is the problem. the horns only get power (12 volts) to them when they are supposed to sound. So something is sending power to the horn when it shouldn't.

Find the fuse for the aftermarket alarm and pull it. It is probably in the box that is the alarm controller or in a wire leading to it, not in a Lexus fuse panel. If that doesn't stop the horn, do the same thing for the stock Lexus horn fuse.

Diagnosing electrical shorts and opens is a time consuming thing. You need to know the electrical circuitry. If you don't, you will spend a lot of time fumbling around trying to figure out where to look. A Lexus tech at $100 an hour that knows how the car is wired will probably fix the car in less time (and therefore less money) than some one who is hunting and searching at say $60 an hour.

dmanwi

One independent mechanic was stumped and said there is something 'really wrong' take it to the Lexus dealership. My relative took it there and they had it a few days and said the wiring harness? needed to be replaced which would be a lot of work and cost $4,000. They took it to another independent who found the short in the wiring harness and simply spliced out the bad section and rewired. It seems to be fine now although I would have wanted to know what the heck caused it.

I wonder if that is the reason the seller had it for sale in the first place.

Thanks for the suggestions.

litzdog911

I wonder if this car was ever in a flood?