Dr. Gizmo Column

"Dr. Gizmo"
By Phil Arendt

Electrical Connections Have Built-in Corrosion Resistance 

Question 1
I am an avid reader of your column and greatly appreciate your automotive insight and advice.  A common condition that is frequently given as a possible fix is to check for loose or corroded ground connections.  Is there an application or lubricant you can recommend to apply to these connections that might resist corrosion and maintain a good connection?  Also, many car manufactures are now recommending 6,000 mile oil change intervals, have you changed your recommendation of 3,000 mile oil changes? B.W., Oakwood Hills, IL

Answer 1

Thanks for reading the column.  In the manufacture of vehicles carmakers use materials in electrical connections that resist corrosion.  It is not recommended to use grease or other products on ground connections.  Certainly over time corrosion might develop in between layers of connections and often they loosen especially in high mileage vehicles.  Sometimes the metal under a connection corrodes causing the trouble.  When a connection causes trouble it might need a thorough cleaning.  Sometimes all it needs is tightening.  What action is needed to cure a condition is determined on a case by case basis.

One of the most common connections that corrode or become loose are the connections on the battery.  Many people believe they should apply corrosion prevention grease to the battery posts or install a felt washer around the post that carries a preventive greasy compound.  More often than not such products do indeed prevent corrosion but the greasy substance eventually causes a poor connection that causes electrical problems.  The best solution is to monitor battery connections.  When corrosion develops, disassemble the connection.  Clean them with sand paper or non-metallic brush inside and out until the mating surfaces are sparkling clean.  Then, reassemble.  No goo is necessary.

As for oil change intervals, I remain steadfast to 3,000 miles oil and filter changes.  And with more turbo-charged engines arriving on the scene, it’s even more important than ever to consistently change the oil and filter at 3,000 mile intervals or sooner.

Heat Causes High A/C Pressure 

Question 2
I own a 2006 Ford F-350 Super Duty truck with a 6.0-liter diesel engine.  I love my truck and use it for work down here in Florida.  The only problem is that the Freon blows a valve in the air conditioner.  When this happens the air conditioning quits.  I have been to two different shops for the trouble but they cannot find the cause.  One shop replaced a pressure valve.  The other shop did a bunch of tests and can’t find a cause.  The second shop told me that when the pressure in the system rises above 350 pounds per square inch the pressure valve is designed to open and relieve pressure but they are not sure why pressure exceeds the limits of the valve.  With summer on the way I need to get this fixed.  Do you have any suggestions?  T.K., email

Answer 2

Move to northern Canada.  Problem solved.  All kidding aside after researching professional web sites your favorite shop might consider testing the operation of the electrical clutch on the cooling system fan.  Research found that on several occasions the temperature of the air conditioning condenser rises too high due to a malfunction in the fan.  When the temperature rises, so does system pressure.  Replacing the electronically controlled fan resolved the trouble in several vehicles.

 

Concern Over Heater Repair Costs

Question 3

I have a 2004 Honda Accord with a troubled heater.  If I set the control to maximum heat cool air comes out of the vents.  It I turn the knob one notch down I get plenty of nice warm air.  I went to a repair shop that has been maintaining my vehicle for a few years.  A technician tried to perform some tests but his test equipment would not work with the computer that controls the heating and air conditioning.  He did do some electrical tests and found everything normal with a motor that changes the temperature.  He is not sure what is wrong but says that it is likely the control panel module is faulty.  He says he is not sure if replacing the part will cure the trouble.  He suggested that I take the car to a dealer to make sure.  He said he will install the part if the dealer verifies it is the cause of the trouble.

My dealer service is expensive.  Do you think replacing the heater controller will fix the trouble?  C.G., email

Answer 3

I appreciate your concern over the cost of your dealer’s service department.  After all with labor costs generally around $115 per hour the cost of repair rises quickly.  Fortunately, generally speaking minimum diagnostic test charges are 30 minutes to an hour.

I also understand why your independent shop technician is suggesting more tests at a dealership.  The part is expensive.  If he installs it and it does not cure the condition he cannot return the part for a refund or credit. Then you will be charged for labor and newly installed part that did not correct the trouble.  This is a poor situation that can cause frustration for both of you.

So, how can this be resolved?  You could live with the condition.  You might search for another independent shop that has a repair manual that can guide a technician through testing procedures and has the diagnostic equipment to perform tests.  Another alternative is to set an appointment with your dealer who is required by contract with the auto manufacturer to have a factory trained technician, repair manual and tools including diagnostic equipment to repair your make vehicle.  The decision is yours.  If you authorize your technician to replace the part, cross your fingers that the condition is cured but if not be prepared for that as well.

Don’t Guess

Question 4
I own a 2006 Ford Expedition.  The front passenger window stops when powering it down and then it won’t go back up.  If I wait a while I can close the window but sometimes it takes several attempts before it closes.  It does not matter if I use the switch at the driver’s control or the one in the right front door.  All the other windows work normally from the driver’s door or at their respective door switches.

Do you think the motor is bad?  C.J., email

Answer 4

The symptoms suggest that the motor has a fault but it is possible a relay or even a switch has a fault.  If you are an experienced do-it-yourselfer consider testing the switches and relay before installing a replacement motor.  After all, it may be fine.

Wiring Needs Extensive Probing

Question 5
After I start my 2001 Dodge Grand Caravan the power windows, radio and windshield wipers quit after about a minute.  If I shut off the engine and not the ignition switch the wipers, radio and power windows will come back to life.  Unfortunately, once I start the engine about a minute goes by and the equipment shuts off again. 

I took the van to a repair shop.  A technician who has been servicing the van for many years said it’s likely there is a problem in the wiring.  He might need many hours to find the trouble.

My van is in great condition but with 190,000 miles I don’t want to put too much money into it.  Can you help?  B.L., email

Answer 5

A lot of work can be accomplished in one or two hours.  If you want to have this repaired you will need to leave the vehicle.  A check of computer modules must be accomplished.  The cost should be less than an hour of labor. 

If modules check okay it is time to troubleshoot wiring.  The use of a wiring diagram will help your technician locate the power and ground circuits of the affected devices.  Since your vehicle is older more than likely he will find a corroded connection or perhaps loose or chaffed wiring is the cause of this condition.

Faulty Axles Impair Transmission

Question 6
I have a 2006 Dodge Charger SXT with an automatic transmission that won’t shift out of first gear.  I took the car to a local transmission shop.  A mechanic said tests found nothing wrong in the transmission.  He determined two sensors on the rear wheels quit working.  They were not sending speed information to a computer that controls the transmission.  He replaced the sensors but the trouble continued.  Now he says the axles need replacing. 

My car has 22,000 miles and a 3.5-liter motor.  The mechanic says there are magnets in the rear axles that the sensors use to send a signal to the transmission computer.  He said the magnets must have fallen off.  I find this hard to believe.  The axles are expensive.  What do they have to do with the transmission?  M.G., email

Answer 6

This indeed is unusual.  Magnetic rings are supposed to be on the rear axles.  Why they disappeared is unclear.  Perhaps corrosion is to blame. 

As the axles rotate the magnetic rings pass quickly over the speed sensors.  This creates a voltage signal that the computer uses to determine transmission shifts points.   Without the magnetic rings the sensors do not develop a signal and the transmission remains in low gear.  To fix the trouble replace the axles.

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@hotmail.com  03/18/2013 ® DR. GIZMO © 1989-Present