"Dr. Gizmo"
By Phil Arendt
A/C Warms When Cruising
Question 1I have a 2003 BMW 760 Li with air conditioning that has my shop puzzled. When the engine is idling or when I’m stopped the temperature of the air blowing from the system when set to full cold hovers around 60 degrees. When I’m driving on the highway the temperature drops to near 50 degrees. The trouble is that after I drive 15 minutes or more at cruising speed the temperature at the vents rises until it is the same temperature outside the car.
My repair shop has done
extensive tests. They found codes
related to a fan at the front of the car and a sensor. They replaced the sensor and the code for
that is now gone. They also drained the
system and recharged it. This did not
cure the problem. Further tests still
show a problem with the fan but they say it is working fine and they don’t want
to replace it unless they are sure that is causing the trouble. At this point the car is not repaired. They think the core in the dash is freezing
but they can’t verify the trouble.
Do you have any
suggestions? W.L., email Answer 1
Winter is on the way. You need the air conditioning system to remove humidity from the cabin to defog the windows.
Generally, when an
evaporator core freezes before the unit becomes a block of ice, ice pellets
blow from the vents. If you or your
passengers have been smacked with ice pellets your shop needs to know. This verifies the core is freezing. If this is the problem your shop needs to
find the cause.
If ice chips are not
shooting from the vents the problem is caused by a fault in the fan or fan
circuit. It appears the circuit is
functioning as designed so likely the fan has an affliction and needs
replacement.
Battery Replacement Leads To
Trouble
Question 2The battery in my 2001 Mitsubishi Montero died. It has a 3.0 engine. I installed a new battery and now the engine stalls upon starting. I can keep it from stalling as long as I press on the gas pedal. I can drive without any problems and it does not stall when I come to a stop. The check engine light is not on as I drive or after I start the engine. It only stalls when I start.
I went to an auto supply
store where tests found no codes. They
have no explanation for the trouble and suggest I take the vehicle to a
shop. Do you know what’s wrong? T.M.S., email
Answer 2
Sometimes when a battery fails
computer modules lose their memory. This
might be what has occurred in your vehicle.
Drive ten miles in normal
traffic at highway and residential speeds and return home. Once home don’t shut off the engine. Park and allow the engine to idle for 20 or
30 minutes before you shut it off. If
the modules are operating normally all of your efforts will cause the modules
to relearn functions and communications.
This might cure the condition. If
not it’s time to head to your favorite repair shop for diagnosis.
Aftermarket Radio Might Be
The Cause Of Transmission Trouble
Question 3I have a 2004 Volkswagen Beetle that every once in a while the transmission does not shift properly. I went to a transmission shop to have the problem checked out. They did some scan tests and test drove the car. During the drive the transmission shifted normally. The problem they found was that their test equipment did not communicate with the engine control module or any other control module in the vehicle. They suspect there is a broken wire somewhere between the plug where they connect the tester and the car’s computers. Since they specialize in transmission rebuilding and repair they suggested that I go another shop.
A second shop tested the
computers but once again their test equipment did not communicate with any
computer in the car. They searched for
broken wires at several locations and removed the speedometer to check a module
and circuit in there. They did not find
any broken or loose wires or loose plugs.
They think the module in the speedometer is bad but they are not sure
and don’t want to replace it unless they are absolutely sure. They also test drove the car and the
transmission worked fine for them. They
suggested that I drive the car until the trouble becomes worse. They also advised that the car won’t pass an
emissions test until all the computers are communicating with test equipment so
I should have the trouble repaired before the required emissions test.
I love my car. It only has 70,000 miles on it. It’s in great condition. I take great care of it and even updated the
radio so that I can use my cell phone through it. It’s never given me any trouble until
now. The transmission acts up once or
twice a week. It’s as though it does not
know when to shift. When the problem
appears no warning lights turn on. It
may happen one time and afterwards everything returns to normal. Do you have any suggestions? Do you know what’s wrong? C.H., email
Answer 3
The good news is it is
likely there is nothing wrong in the transmission. Two shops have driven the car and agree the
transmission is not in trouble. The bad
news is both shops have attempted to communicate with control modules and have
been unsuccessful. The second shop did a
lot of work tracing circuits without finding a direct cause for the
condition. They only have suspicions.
The really bad news is that
suspicion points to the recently installed aftermarket radio. Ask your favorite shop to fully disconnect
the radio including the wiring harness that modifies the factory original
wiring. Doing this might restore communication
between all the control modules and resolve all issues. If so, the transmission should return to
normal operation. After this your next
step is to return to the facility that installed the radio for a resolution.
Emissions Warranty Might
Cover Repair Cost
Question 4I have a 2009 Chevrolet HHR with a 2.4-liter engine and 32,000 miles. The check engine light is on. I went to an auto supply store for a test. The employee found code PO449. He said it indicates a problem in the evap system solenoid. He said he could get me a vent valve but he also said there might be other troubles causing the light to turn on.
I bought the car last
year. I really like it. Do you think replacing the valve will cure
the trouble? S.B., email
Answer 4
It’s possible replacing the
valve will cure the trouble but your parts store employee is correct. There may be other problems in the system
causing the issue. It might be caused by
corroded terminals in a plug or faulty ground connection.
Your car has very low
mileage and a problem such as this could be repaired under a warranty. Consider discussing the issue with a service
department manager at your local dealership.
If the repair is covered by an emissions warranty or another warranty
you won’t shell out a dime for the repair and your car will have factory
original repair parts.
Replacement Engine Module
Due For Programming
Question 5The other morning my 2002 Ford Ranger cranked but did not start. A friend who knows a lot about Fords took a look at it. He had a scan tester and found that the engine module was bad. He suggested getting a used one with the same part numbers as the one in my truck. I searched EBay, Craig’s List and a junk yard and found one. He installed the part but the antitheft system prevented the engine from starting. The theft light was blinking. Now he says the module needs reprogramming but he does not have the tool to do the work. He thought that if he installed a part with the same number the engine would start.
Do you think the replacement
module is bad or does it need programming?
K.B., email
Answer 5
Your friend apparently has a
tool to determine if a module has a fault so perhaps he should test the part. If it has a fault it’s time to return it for
another if possible. If the module
passes tests it likely needs programming.
If his tool can’t complete the task consider towing the vehicle to a
shop that has the equipment to program the module.
Also, more than likely a
shop will request that you have two keys.
The programming likely needs two keys to accomplish the task.
New Relay Fixes A/C But
Clicks
Question 6The air conditioner in my 2005 Volkswagen Passat quit working. I took it to a local repair shop where they found a relay was bad. They replaced the relay and the air conditioner is working. The trouble is that when the air is on I hear a constant clicking sound. I returned to the shop. They told me that the new part is clicking. They replaced it again and the clicking continues. They don’t know what is causing it to click and said it might stop once I drive more.
The clicking is
annoying. Does this seem right to
you? D.H.A., email
Answer 6
No. The relay should not constantly click. More than likely there is an issue in the
circuit such as a loose or corroded terminal.
Maybe there is another relay in the system that sends power to the
recently installed relay that has a fault.
Issues such as these are causing the annoying clicking.
Ask the shop owner or
manager to consider these suggestions when you return to the shop.
Thank you for all the 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 mailto:drgizmo@hotmail.com. 09/23/2013 ® DR. GIZMO © 1989 - Present
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