Archive for the Auto Maintenance Category

Car Stereo and Speaker Installation

Posted in Auto Maintenance, Electronics on April 21, 2011 by themidnightengineer

This is a continuation of where I last left off regarding my battery drainage problem. The factory amplifier unit had a short circuit so I had to remove it to solve the battery problem. But without the amp, I cannot listen to any music in my car. To replace it, I could either order it from the dealership or try to find a used one in good, working condition from a junkyard.The first option would cost too much (the dealership quoted over $700) and the second option would take too much time and hassle.

Given these choices I decided to replace the factory installed stereo unit and speakers with aftermarket equipment. I’ve been wanting to do this anyway since my car is 15 years old and the existing stereo unit was obsolete.

I purchased a Kenwood KDC-MP245 CD Receiver from Crutchfield. It has four pre-amp channels at 22 W RMS/50 peak of power each.

I also ordered 2 pairs of Polk Audio db651s 6 1/2″ speakers. These speakers are rated for 6 – 55 W of RMS/165 peak power, frequency response of 50 – 22,000 Hz. and a sensitivity of 92 dB. Sensitivity is another term for efficiency. It is a measure of how well the speaker converts audio signal power into sound as opposed to being wasted as heat. The higher the better.

I also got a 50′ spool of 16 gauge blue speaker cable. When replacing factory default speakers with new ones, there are generally two options for wiring the speakers to the stereo unit: use existing wiring or route new wiring. The first option is less work. The second option means you have to take things apart but the sound quality is better. Specific to the case of my car, the factory component amp was a big factor. The existing stereo fed audio input to the amp. In turn, the amp was driving two tweeters, four speakers, and a sub-woofer. The existing wiring configuration was useless for a four speaker only setup. I went with the second option.

The most difficult part of installing aftermarket car audio equipment is routing the new cabling.

The front two speakers were located in the doors which meant that I had to take the door panels off.

There is a wire harness that goes from the door speaker to a junction box in the interior of the car.

The plan was to thread the new cable through the wire harness. But I had to clip and pull out existing speaker wiring to create slack first.

After that, I threaded through the new cabling. The positive and ground leads were fastened to the speaker terminals with crimping nuts.

Making the back end connections at the stereo unit was pretty straightforward.

Installing the rear speakers involved taking the rear passenger seating off.

Overall, it was a big project that took three days to complete. Because it involves access to electrical schematics/wiring layout, knowing where things are located in the car, some skill in electrical work, troubleshooting, and taking apart many different sections of the car interior, it is not recommended for the faint of heart.

The following videos demonstrate the results.

Mysterious Car Battery Drainage Problem Solved

Posted in Auto Maintenance, Electronics on November 10, 2010 by themidnightengineer

As mentioned here, I had a problem where something was draining the juice from the battery in my car. I was able to find out, by troubleshooting the fuse boxes, that it had to do with the stereo system.

Removing the radio unit, however, did not make the problem go away. There was something else that was causing the drain.

After consulting the schematic from my Haynes repair manual and much searching, it turned out to be the stereo component amplifier, a separate unit that was located below the front passenger seat.

The green outline boxes in the photo above shows signs of water stains on the unit.

Opening the unit and inspecting the circuit board inside reveals water damage causing short circuits.

AC/Heater Control Unit LCD Backlight Repair

Posted in Auto Maintenance, Electronics on September 18, 2010 by themidnightengineer

Recently the backlight for the liquid crystal display for my dash-mounted AC/Heater Control Unit stopped working. I disassembled the unit to inspect the innards and discovered that the backlight had been provided by three incandescent lamps soldered on a PCB whose filaments had expired.

These tiny light bulbs were sheathed by translucent green rubber “condoms”. Before I disconnected the PCB from the unit, I measured the open-circuit voltage (~9.7 VDC) across the leads of the bulbs.

I also noted the polarity of the leads using a marker on the PCB. This is because I was planning to replace the bulbs with LEDs. LED is a polarized device, with cathode and anode leads, unlike an incandescent bulb. The polarity of the supply voltage across an LED matters, just like with any diode. I do not know why Toyota never designed this backlight using LED lights in the first place, but being that it is a solid-state device, it is much more reliable and efficient than a filament bulb.

I purchased four 5mm white LEDs from Radio Shack that were selling for $1.99 for a pack of two. These LEDs were rated for a luminosity of 7000mcd. I also bought 270 Ω resistors to be connected in series with the LEDs as current limiters to provide a forward current of 25 mA and a forward voltage of 3.3 VDC.   This link has a useful current limiting resistor calculator for simple LED applications.

The following photo shows one of the bulbs (bottom) extracted from the PCB next to the LED (top).

I soldered the LEDs and the resistors onto the PCB. One lead of the resistor was soldered into the via marked positive. The anode of the LED was soldered into the via marked negative. The cathode lead was fed through the lamp base mount hole and soldered onto the other lead of the resistor for a series connection. I covered the  LED/resistor pair on the right with heat shrink tube to prevent possible short circuiting with an adjacent IC.

This view shows the LEDs on the other side of the PCB after the soldering was completed.

I took the PCB to the car to connect it back to the AC/Heater Control Unit. I turned the ignition half-way to provide power. The LEDs turned on. I could tell they were much brighter than the previous bulbs.

I reassembled the unit and covered the LEDs with the green condoms. This is how the display appears now.

Total cost of this repair job: $5.32

A 15 Year Old Car is like a Woman

Posted in Auto Maintenance, Troubleshooting on August 30, 2010 by themidnightengineer

Two words: high maintenance.

There’s been a vexing problem with my 95 Lexus ES300 ever since I purchased it for $700 in cold hard cash from my friend Taek back in February. The car constantly needed a jump-start. Taek had the battery and alternator replaced but the issue didn’t go away. When the most obvious solution fails, the problem becomes bigger and more mystifying. The battery was replaced two more times, poor quality being the suspect. No dice. The rear trunk latch was faulty and so I fixed that. I also unplugged the lights for the glove compartment and trunk for good measure. I also discovered and repaired a damaged electrical cable harness under the hood. Each of these issues could have had a bearing on the starting problem and each time I thought I had hit upon the root cause. Yet the problem stubbornly remained. Something was draining the charge on the battery. Leaving the car parked for more than 24 hours resulted in a dead battery and ignition failure, requiring a call to AAA to request a jump-start. However, disconnecting the cable from the positive terminal on the battery prevented the drain and served as a temporary fix.

I took the car to the Lexus dealer and explained the situation. They did some tests and told me that I needed to replace the battery. That was singularly unhelpful since I had gone down this route already. I suppose it is possible that three different batteries in a row could all be bad but its highly doubtful.

This weekend I measured the current drain on the battery using my multimeter.

This current draw is equivalent to leaving the car door open (which results in several lights being turned on).

My car has three fuse boxes (two under the hood and one below the steering wheel). To pinpoint which electrical sub-system was causing the drain, I pulled each fuse one by one until I saw the current draw drop to a nominal level.

This is one of the fuse boxes located under the hood. I pulled out the RADIO fuse.

The reading on the multimeter dropped from ~ 0.59 A to ~0.03 A.

So now I know exactly what’s been causing the drain. For now, I will leave that fuse unconnected.

Troubleshooting this car is like playing Whack-A-Mole. You take care of one problem and two or three other problems emerge. Next, I need to figure out why the windshield wiper fluid refuses to spray.

Replacing Brake Pads on the Car

Posted in Auto Maintenance on July 2, 2010 by themidnightengineer

I took the car to my usual mechanic last Wednesday to have some work done and he was totally booked. So I decided to take matters into my own hands.

I carry an aluminum pipe in my trunk for taking the lug nuts off the wheels. The wrench is not enough. The nuts are so tight that you need the extra leverage to turn them. It was Archimedes who once said, “give me a lever that is long enough and I can move the world.” The pipe is also handy in case you need to encourage some random road rage miscreants into civility.

Here is what the brake assembly looks like with the tires removed. You have the caliper, the discs, and the pads.

Take the calipers off. Clean the discs using brake cleaner spray. Remove the worn pads.

Install the new pads. I get mine from the Toyota dealer.

Take out the sliding pins and clean them. Apply a fresh coating of high temperature grease.

The following photo shows the pistons inside the caliper. When you step on the brake pedal, these pistons apply pressure on the pads which then clamp on the disc.

In order to put the caliper back into place, these pistons have to be squeezed in. It helps to remove the cap of the brake fluid reservoir on top of the master cylinder to relieve the back pressure in the brake fluid line.

A lady who lives in the building next to me saw what I was doing and wants me to work on her car also. Great.

The joys of owning a 15 year old car

Posted in Auto Maintenance on June 21, 2010 by themidnightengineer

I own a 1995 Lexus ES300.  Last Saturday, the battery died (again) on my car so I had to call AAA to get it jump started. Getting the car started is great but I still had to figure out why the battery died in the first place. The cause could either be a short circuit or a light bulb that was kept on and drained all the juice.

A couple of weeks ago, I had a dead battery problem also. Turned out a composite electrical cable inside the hood compartment was damaged. This cable, among other things, plugs into the alternator. What happened was this cable was loose and rubbing against an adjacent engine belt. While the engine was running, and the belt turning, it ripped into the cable like a band saw. If any of the wires inside touches a ground, this constitutes a short circuit and will drain the battery. I spliced the cable, got the car functional again, and thought I had solved my battery related ignition start issues. Until Saturday.

After the AAA guy gave me a jump-start, I drove the car for about 30 minutes to recharge the battery. While I was driving, I thought about it. The most immediate suspect that came to mind was the trunk latch. The other problem that I had with this car is that the trunk would refuse to close properly. Sometimes, while I was driving, and especially when I hit a bump, the trunk would pop open. There have been many times also when I would park the car and the trunk would be open slightly. So I would have to close it again. When the trunk is open, there is a small light bulb inside that goes on. Needless to say, if I parked the car and forgot to check if the trunk was open and left it like that for the entire night, then the battery would be weak the next day.

I unscrewed the lock mechanism unit of the trunk and took it out to inspect it.

There were a couple of latches inside the unit which locks onto a metal loop on the trunk cover. On each there was a metal post (highlighted in green) which looked like they’re supposed to hold something. I looked inside the trunk again and found this.

Ah…the plot thickens. This spring is supposed to go between those two posts. As the photo shows, a piece of the bottom hook had snapped off due to metal fatigue and the spring had popped out. Using pliers, I installed the spring back where it belonged.

The trunk shuts fine now. For good measure, I disconnected the trunk light. Hopefully, this will resolve my battery issues once and for all.