How To Repair
  2002 Toyota Camry SE 2.4L 4-cyclinder

© 2013 Brian Mork

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This web page contains a narrative log and pictorial essay to maintain a 2002 Toyota Camry SE with 2.4L 4-cylinder engine with 162,000+ miles.  At the bottom, I also have some simple graphs aggregating lots of data on costs.  This page is meant to teach you, document technical data, and perhaps most of all motivate and encourage you as you try to figure out your non-working car. I also have web pages about my 230,000 mile 1994 Suburu Legacy with 2.2L and a 1989 Dodge B250 Ram Van with 5.2L engine

always appreciate your link back to this page so Google thinks what I say is important!

Before you start work on a car project that may take several weeks,
consider canceling insurance or doing "storage" insurance. My insurer used to provide a "storage" option that provides only comprehensive coverage and drops the cost of a newer vehicle from $52.50/mo down to $5.00/mo.  More recently, they've changed the definition of "storage" to mean "state mandated minimum insurance," and for a Dodge van discussed in the other web apge, that change dropped cost from from $27.17/mo to $6.70/mo. Or, if you can handle the risk, you could remove ALL coverage including comprensive and save a boatload of money.

Air Conditioner
New Tires & Tie Rod NOT connected!
Rear wheel bolt stud replacement (remove badly rusted on rotor)

Pictures for Reference as You Read about Air Conditioning.

Click on any picture to see a close-up view.

O'scope on the A/C compressor speed sensor.
  Positive and negative excursions of 350 mVolts into a 1 Kohm load resister. Removing the resistor allowed the sensor to produce about 400 mV.  You can watch a video of the A/C speed sensor when I manually apply +12 volts to the compressor clutch.

After the pressure was brought up to about 200 psi, I disengaged the clutch and the pressure settled back to about 165 psi.

I decided these readings didn't mean mutch since it was about 45 degrees F at the time.

High pressure side pressure meter hooked up and test wires in place. Only the yellow wire was being used at this time to energize the clutch coil.

Leaning over the driver side of the  front wheel looking at the relay and fuses.

I  removed the relay and stuck the blue electrical connectors in place so I could grab the connection better with a pair of aligator clips.

Once I confirmed the relay was not working, I decided to cut it open and investigate.

Anvil, chisel, hammer...

Silver legs energize the coil to magnetically operate the contacts.  Put 12 volts acros the 170 ohm coil and you should hear a "click". The brass colored legs are suppose to close with low resistance.  This relay clicked fine, but  made no contact between the copper feet.

Fuse and relay map inside the lid of the fuse box. The relay we care about is labeled "MG CLT" for MaGnetic CLuTch.




Fall 2012

The air conditioning started operating intermitently.  A green light would flash on the panel button, and the compressor failed to operate, so of course no cool air came out.  Eventually, it totally quit working and all I got was a flashing green light after about 5 seconds of "on time".  Big tip for you up front:  you can bypass all the hassles I had by noting if the compressor comes on during those 5 seconds and then stops, or whether it does not engage the clutch at all.

I took this to the shop and they quoted a bill of $600 to replace a sensor on the compressor pump - $300 in parts and $300 in labor.  They said the sensor cannot be purchased separately from the compressor.   Uggh.. I wasn't ready for this, so paid him a $70 diagnostic fee and took the car back home.  We'll live without air conditioning for the winter.

March 2013

I had good luck with Omega Environmental Technologies (retail covered as AC Compressor Pro) when buying a compressor installation kit for my old Dodge van, so I ordered a compressor kit for the Toyota.  I later found out the switch on the compressor is not a pressure switch but an inductive speed sensor like an ignition pickup coil.  Plus I later found out it did not come with the compressor!  I figured at least I'd pay the repair shop to install it because I didn't want to get into recovering the freon with a home-made dry ice and alcohol cold bath and old propane bottles.

I took the package to the shop and he said he'd get back to me with a quote. I reminded him about the diagnostic work he had already done, and told him I already purchased the replacement compressor kit.  He said, "Oh, you already know what you want done?  Let me go get a quote for you."  He came back with a quote of $700.  What?!  Labor was $300 last fall, and now it's $700.  Including parts, that's slightly over $1000 to replace a broken sensor!!  Something is not right.

Well.. he explained that it's not a pressure sensor, but rather a speed sensor.  To replace the sensor, he has to replace the compressor.  To replace the compressor, he has to replace the expansion valve,  to replace the expansion valve, he has to replace the evaporator, and to replace the evaporator (which I hadn't purchased yet), he has to disassemble the instrument panel.  Uggh.. really.. this is gross.   The story was changing quickly.  I didn't know if he was intentionally trying to squeeze me, or whether he didn't care to estimate with any degree of fidelity better than what was required to get my work signature.

I took the $1200.00 repair problem home a second time.

Early April 2013

I called the local Toyota dealer and asked if I could buy the sensor and fix the problem myself.  Sure, they said.  It's a $117.73 part.  What?!  You ~can~ buy the sensor separately?  Why did the repair shop say otherwise?  I researched on the web with a proper search for "a/c speed sensor" instead of "a/c pressure sensor" and discovered that the entire freon pressure needed to be emptied to replace the sensor. 

I had already paid $300 for the compressor kit.  They will take it back, but charge a 25% re-stocking fee.  Does anybody believe the repair shop might reimburse me for taking me unecessarily down this path?

I decided to go to a different shop and get a quote to simply empty the system, replace the sensor, and pump up the system again.  I asked for a quote and they called back to say the sensor could not be purchased separately.  Hmmm... this story is sounding repetitive.  I let him know Toyota offered to sell me the sensor and he said that if I brought it in, he'd be happy to evacuate the system and replace the sensor and pressurize the system for $173.10 in labor costs.

At least this was reasonably priced, so all I had to do was make sure the sensor was bad.  I no longer trusted the first repair shop.  I poked around on the web and found an article by Dan Marinucci specifically addressing blinking green dashboard lights and a/c speed sensors (Motor Magazine copy or local copy).  This article also confirmed that replacing the sensor would require depressurization of the system. [later note - Dan Marinucci's article is not correct; the green light blinks for other reasons I found out; he has not replied to my email.]

Thursday (Scoped the sensor)

With confidence that I now understood what the sensor was, I decided to remove all the fancy car computers and controls, and just let the engine manually spin the compressor (+12 v to the clutch coil) and measure the inductive sensor with my oscilloscope.  This was fine to do since I was sure that the system had sufficient gas pressure and oil to not burn up the compressor.

I connected a scope directly to the speed sensor and recorded a speed sensor video.  Look at the photo in row1 column1 above first, and then watch the video.  Right at the beginning of the video, you can hear the compressor clutch engage, and see the engine load down, and then it stabilizes back at a higher idle RPM (pulses closer together).  When I release the clutch, the pulses go away.  Everything looked good!  Contrary to the repair shop quote, the sensor was not bad.

Let me repeat: 
Does anybody believe the repair shop might reimburse me for taking me unecessarily down this path?  I cannot believe they were going to charge me $1200.00 to fix a phantom they fabricated.

Still, the compressor won't run on it's own.  Apparently the green flashing light and no-run will occur if the compressor speed doesn't track well with the engine RPM due to slipping belts.  I diddled with the belt and other little things but became convinced that when power was applied to the clutch, the compressor immediately engaged and the compressor worked fine.  No slippage even though the green light came on.


Since the compressor worked fine, I went back to see if there is some other cut-out that was preventing the system from running.  I figured I better check the hi/lo and operating hi/lo pressure more carefully.  Everything measured low.  I referenced a generic pressure chart that came with the pressure gauge and connectors.  The chart didn't even go below 75 degrees and I was working in 45 degree weather.  I decided the pressures probably ~should~ be low!

I decided to wait until warmer weather.

Friday after Work

Came home, changed clothes and got outside before the temperature started dropping in the evening.   Pressures looked good.  I monitored the high-side pressure as I manually clicked on the clutch coil while the engine ran.  Pressure slowly built up to about 225 psi and then the radiator cooling fan turned on and the pressure immediately dropped down to about 170 psi.  Repeated over and over.

The small diameter tube going into the passenger compartment evaporator was a bit warm.  The larger diameter tube coming out of the firewall was a bit cool.  All seemed correct.

I went back and clicked the a/c on and off a few times from inside the car.  And then it hit me. It was taking about 5 seconds for the green light to begin blinking, but because I had just been clicking the clutch on and off, I was used to the sound and the engine response.  The clutch wasn't even trying to come on!  Wait a second.  Dan
Marinucci's Motor Magazine article was clear that the only reason for a blinking green light was a compressor running at the wrong speed.  Mine wasn't running at all!  When I had the compressor electrical plug unplugged to manually turn on the compressor, I accepted that the car computer complained about the speed sensor because it was unplugged for access to the clutch power wire.  But when I put the plug back together and sat in the car, I should have heard the clutch at least come on for a few seconds before the car complained about mismatched speeds.

I did some more web searching about speed sensors and there were multiple rumblings about blinking green lights being fixed with a new a/c relay in the fuse box.  I decided to check mine.  I found the relay using the key printed on the fuse box top.  I pulled the relay and poked and prodded with a voltmeter on the car and an ohm meter on the relay.

With the relay out of the vehicle, I monitored the relay coil connection from the car computer and indeed it was trying to turn on the compressor for about 5 seconds before cutting power.  Interesting.  Why wasn't my compressor turning on?  I pulled the relay and used a 12 volt battery across the 170 ohm coil.  Nice strong click, no sticking. I went back to the car and used a wire to close the coil output contacts.  Instantly the compressor came on.  Bingo!

I went back to the house and measured the relay contacts and I clicked the coil.  Nothing.  Megaohm resistance across the output.  Nice click, but no electrical contact. 

Back to the fuse box, I pulled the fan relay and stuck it into the a/c relay position (it's coil measured almost exaclty the same resistance, so I knew they were compatible).  Voila!  the a/c system was working perfectly.  I didn't leave it on because I had no cooling fan, but I had positively confirmed the problem.

Required: one new a/c relay.  I did pop the old relay apart to see if I could learn anything.  Maybe a slight amount of visible corrosion in by the contacts, but nothing gross.

The air conditioning problem had been one total fiasco by a commerical repair shop:
Was it malicious intent to rip me off?  I think it was simply laziness.  They didn't care what the problem was.  They figured if I wanted to get it fixed, they would just fiddle around putting new things on the car until it was fixed.  They were factually wrong about buying a sensor, and they just didn't care to courteously save me me money by doing the minimum repair possible. 

Need I say how offensive that is to me?   They would have put a new $1100.00 a/c system in the car and it wouldn't have worked any better.  Eventually they would have found the relay.  Then what?  Say I'm sorry, and bill me $1100.00 + $17.00.  They probably would have eaten the $17.00 cost and never told me of their mistake.  I'm sort of fed up with car repair shops right now.

Last time, they quoted me $1600.00 to fix a Dodge van and really all it needed was a new intake gasket (but they put the vacuum line wrong so I had to fix my ventilation control system when I got it home), and they wanted to bill me $450.00 for an exhaust manifold I found for $75.00 on the internet.  I have wanted to believe these guys are a home-town good deal.

They are proving to me that I need to go elsewhere.  I did go back and talk to the manager. He said, "Oh, yea, I think that was Mike (or some other name I can't remember).  He should have checked the relay first before giving you the estimate.  He no longer works here."  Pass the buck.  Okay.  I got it.

For all the hobby wrench turners out there - I have been tempted to believe it's not worth my time to always be fixing cars.  And then I learned again, it IS worth my time to know enough to figure out what's wrong.

[update: nearly 4 years later in 2017, the a/c system is still working fine.]

Spring 2014 - New Rear Tires

Road trip.  new tires.  tie rod bolt sloppy loose AFTER traveling 400 miles.  Took it back to the repair shop. Fixed it with a new tie rod.  When done, they slammed tires on with a power impact wrench, which turned out to be carlessly over tight compared to the spec'd 80 ft lbs, causing a latent effect I didn't find out about until 3 years later.  ]

January 2017 - Wheel Bolt and Stuck Rotors

bolt to pop off rotorsI planned to only rotate the tires.  When I got to the rear passenser side, I unscrewed one of the wheel nuts and the entire bolt snapped.  The only way that could  happen was if the last person who put on the nut way overtightened it and stretched or fractured the bolt.  In any case, I had to get the brake rotor off so I could get the wheel bolt stud out of the hub.

My brake rotors were really rusted on.   The only way I was able to get it off was to follow an idea I found on youtube to remove stuck rotors.  The only difference is that my caliper bolt holes didn't clearly line up with the rotor.  They bumped the inner rain shield and their wasn't room for the "foot nut".   So used 3/16" bolt with only one nut.  Instead of the nut that touches the rotor, I used a flat piece of steel about 1/8" thick for the bolt to directly push against, pinched between the bolt and the rotor.  I used two of these - one of the top caliper bolt hold and one on the bottom.  I turned the nut to apply pressure , which wuold have skated all over the steel plate.  Torque was getting pretty high, I'd estimate about 60 ft lb on the nuts and the caliper flanges were starting to slightly bend.  Enough.  With that much pressure applied with two bolts, I tapped on the rotor central part a few times with a hammer and suddenly the entire rotor jumped outward and was free.

mount new stud Once the rotor was out of the way, I tapped on the wheel stud with a hammer to slowly back it out.  I positioned the new one and in order to pull it through the hub and lock it in place, I piled a stack of washers and then torqued the wheel nut onto the bolt.  As I tighted upward of 100 ft lbs, the stud pulled into and mounted firmly in the hub.

Additional Resources

Video of hi/lo pressure readings, and bubbles going by the sight window.
Pressure switch for sale.
Numbers look right, but weak cooling.
A/C relay is the simple fix!

© 2017 Brian Mork. Please contact me using the copyright link prior to commercial use, or reproducing for distribution in a commercial context.