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Friday, May 25, 2012

Just In Case You Missed It, Northwest Herald Dr. Gizmo column dated May 18, 2012


05/18/2012

"Dr. Gizmo"
By Phil Arendt

Climate Control Leaves Motorist Roasting Or Frigid 
Question 1
I have a 2005 Ford F250 Super Duty 6.0-liter turbo diesel crew cab with 106,000 miles with a climate control system like most Ford cars.  My problem is that my climate control unit will go completely dead once in a while.  It's never at a good time.  It works fine for months.  Then one day when I go to the store it works fine.  When I return to the truck the climate control is dead.  At other times I can be driving along and it goes off.  There is no heat, fan, air conditioning, nothing.  Sometimes when it is dead while I’m driving it will suddenly start working.

I have tried to get to my dealership while it wasn't functioning since the truck had 30,000 miles on the odometer.  I would make an appointment and by the time I arrive there the climate control is working.  They want to see it when it is not working.

I drive the truck more on weekends.  Service is not available then.  By Monday it is usually working after I spend a lousy weekend either freezing or frying.   At 30,000 miles I had my Ford dealership check the climate control module.  I was assured it is fine.   Any ideas?  S.F., email

Answer 1
I understand your frustration.  The best time for a technician to examine the system is when it is not working.  Consider driving the vehicle more during the week.  When the system quits, drive directly to your dealership.  When you arrive, do not shut off the vehicle, don’t touch the HVAC controls just go to the service area and show a service manager the trouble.  He may be able to immediately assign a technician to your vehicle to determine the cause of the trouble.

Additionally, since you do not use the vehicle much during the week consider leaving the vehicle at your shop.  Give authorization so a technician can drive the vehicle to and from work so he can experience the trouble with test equipment is hand.  

More than likely, the trouble is caused by a faulty relay.  It’s also possible a loose or corroded ground or power supply wire is causing the trouble.  Since there are several pages of wiring diagrams for the system a technician will need to check several connections for faults.

If you can’t take the vehicle to your dealer when the system fails a technician can perform jiggle tests of wiring to find a fault.  Literally he jiggles wires until he hits the one with a fault.  Once this is done repair can be as simple as tightening a bolt.

In the Dark Over Interior Lights
Question 2
The interior lights in my 2002 Cadillac Eldorado do not turn on when I open the doors.  I can turn them on with the headlight switch.  I checked the fuses, but all of them are fine.  Also, I took the car to a local shop where a mechanic did some tests but he is not sure what causes the trouble.

Can you provide some suggestions?  R.O., email

Answer 2
Keep a flashlight on the dash.  That should cure the trouble.  All kidding aside, since the lights work from the headlamp switch and all fuses are good, we know a short circuit is not the cause of the problem.
 
The system is controlled by a body control module, a light sensor and switches.  More than likely there is a fault in either the light sensor or body control module.  A technician should test these units.  In doing so he should be able to determine which part is not functioning as designed.  If my hunch is correct the light sensor is the culprit.

Air Conditioner Quits When Braking
Question 3
Recently, I purchased a 2005 Mazda 6 with stick shift and a 2.3 engine.  It has 66,000 miles.  The car is in really good shape.  I bought it from a private party.  He gave me copies of all the service records.  He changed the oil every 2,500 miles and apparently followed other services in the owner’s manual. 

The trouble is that sometimes when I brake the air conditioner seems to turns off because warm air blows from the vents instead of cold air.  Once I release the brakes, and accelerate, cold air returns. 

I took the car to the shop that serviced the car on a regular basis.  A mechanic tested the air conditioner and heater, but he did not find any problems.  He suggested that I wait until the problem becomes worse before I return for this problem. 

With summer weather coming soon I would like to have this problem repaired.  Do you think the trouble will get worse?  Do you know what causes the air conditioner to shut off?  J.L., email

Answer 3
Perhaps you should release an anchor and not use the brakes.  I’m just kidding.  I would not want you to have an accident.

Perhaps your technician could consider that the trouble might be caused by a loose connection.  It’s also possible a worn engine mount causes the engine to shift under certain braking conditions.  This could place stress on a wiring harness and open a circuit.

Maybe the insulation on a wire has worn away.  When the engine moves while braking, the circuit might open.

Additionally, a search of factory technical service bulletins found you are not alone.  Apparently, other Mazda 6 owners have cars with similar symptoms.  To cure the trouble Mazda engineers developed a fix that includes reprogramming the powertrain control module. 

Ask your shop manager if they have a factory tool to reprogram the module.  If so, that’s great!  If not, it is time to take your car to a dealer shop to have the problem diagnosed.  The repair might be contained in technical service bulletin number 01-005/08 which covers the symptoms and procedures to reprogram the powertrain control module.

Windshield Wipers Out Of Service
Question 4
The intermittent function of the windshield wipers in my 1998 Jaguar XJR does not work.  The wipers work fine at all speeds except intermittent but when I shut them off by turning the switch they will not shut off until I turn off the car.  Obviously when I shut off the car the wipers might stop in the middle of the windshield and not at the bottom as they should.  I try to shut off the car so the wipers are at the bottom of the windshield but this is difficult.

I have taken the car to two different repair shops.  A technician at both shops has checked the wiring, some relays and the switch.  Both technicians feel that the wiper motor has a problem and needs replacement but they are not sure.  Also, they are having difficulty finding a new motor.

The car is in great condition.  It has 87,000 miles.  I’ve owned it since it was new and have done maintenance according to the factory schedule.  It runs great except for this problem.  Do you think that replacing the motor will cure the trouble?  Do you know of a technician who can repair a wiper motor?  B.W., email

Answer 4
It is likely the trouble is caused by a fault within the motor.  Replacing it is the likely cure. 

As for finding a shop technician who can repair a motor, way back in the old days technicians were trained to repair electric motors such as the starter, wiper and even the alternator but today technicians do not do this type of work.  If you are lucky you may find a technician near retirement age who can do the work but most seniors have moved on to other aspects of their careers.    

If both technicians are reasonably certain replacing the motor will cure the problem it is time to replace the part.  The trouble is that it is highly unlikely that a brand spanking new motor is available.  More than likely the technician who is awarded the repair will install a remanufactured unit. 

Broken Belt Might Have Trashed Engine  
Question 5
I have a 2000 Dodge Neon with a 2.0-liter 4-cylinder engine.  It has an automatic transmission, power steering, air conditioning, antilock power brakes and more.  The trouble is that the timing belt broke.  I had just entered the highway and the engine suddenly stopped.  I coasted to the side of the road and attempted to start the engine but it refused.  The car was towed to a shop near my home.

My repair shop has been in business a long time.  They have regularly serviced my car for about five years.  The shop manager called to tell me that the timing belt broke.  He said that his mechanic is 99 percent sure the valves are bent.  He said that he mechanic checked the valves with a scope.  At the very least the cylinder head will need replacement.  He also said that it is possible that the pistons are damaged but he won’t know for sure until the cylinder head is removed.  He said that if the pistons are damaged the engine might be shot. 

My car has 157,000 miles on it.  I have taken good care of it since it was new with oil and filter changes every 3,000 miles.  The body and interior are in great shape.  Up until now it has not given me any trouble.  Why did the belt break?  Is it due to engine wear?  Do you think the pistons suffered damage?  Is it worth repairing?  D.D., email

Answer 5
I can’t place a value on your car.  This is something you need to decide.

As for why the belt broke, it is similar in construction to the drive belt that turns accessories on the front of the engine.  As with the drive belt, the timing belt wears out.  When it is excessively worn it can jump off gears or break.  As with the drive belt it needs replacement before it breaks.  According to the factory recommended maintenance schedule the belt was due for replacement at 105,000 miles.  If this service was not done, it has served its duty beyond its service life.  If the timing belt was replaced at the specified interval, it is possible a part that guides and adjusts belt tension failed causing this calamity. 

As for damage to the pistons, it is possible they suffered damage due to collision with the valves when the belt broke.  Since your technician used a borescope to inspect the valves he should be able to examine the pistons with the same scope.  However, it is possible to miss damage with a scope.  A scope has optical limitations and can’t provide a technician with a full and clear view of an entire piston.  The best visual exam is with the cylinder head removed from the engine.  This gives a technician a clear view of the pistons. 

Ask your shop manager if his technician examined the pistons with the scope.  If he did and did not see any damage chances are great that there is no damage.  If there is no damage replacing the cylinder head will place your vehicle back in operation.

Stalling Caused By Faulty Module
Question 6
Intermittently, for the last two months my 2010 GMC Sierra with 70,000 miles and a 6.0-liter flex-fuel engine stalls.  It’s as though the ignition key was turned off.  The lights and all accessories work but the engine quits.  When it quits I try to restart but it cranks and won’t start.  Everything looks normal on the dash.  I may have to wait an hour before it will start.  When it starts it runs great as though nothing has happened. 

I have taken the vehicle to three shops including a dealership.  Technicians have checked wiring at several modules.  They have tested modules and the alternator and battery.  They have checked several plugs for loose terminals but they have not been able to find the trouble.  One technician found a memory failure code in an engine module but he was unable to confirm that was the cause of the trouble. 

I love my truck.  I need it for work.  Do you have any suggestions?  R.B., email

Answer 6
With 70,000 miles on your vehicle you spend a lot of time behind the windshield.  This needs to be fixed.

Statistics show that it is rare for an engine control module to fail.  Manufacturers test parts that are returned to them under warranty.  More often than not when a powertrain control module undergoes testing it is found that a technician misdiagnosed the trouble and the returned module is functioning as designed.  Technicians are aware of this and are cautious not to replace a module unless they are absolutely sure it has a fault.  This scenario may be why the engine control module in your truck was not replaced. 

I’m not sure which code your technician found in the computer but it might be a read only memory failure code.  If so, it is time to replace the module. 
  
Thanks for all of your great questions.  Dr. Gizmo can’t wait to answer more.

Phil Arendt is a columnist, consultant and A.S.E.-Certified Master Technician.  Readers may send questions to Dr. Gizmo at P.O. Box 548, Cary, IL. 60013 or e-mail address drgizmo@drgizmo.ws. 5/18/2012 ® DR. GIZMO © 1989-2012

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