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Ironing Out Cold Solder Joints
Q: I have an '01 Corvette with 40,000 miles. Recently, the digital temperature display on the automatic climate-control system has gone very dim—it can only be seen at night, and even then it's barely readable.
Can you recommend a fix for this issue? I'm hoping I don't need to replace the whole display.
Jason A. Bryan
West Des Moines, IA
A: This is a common problem on C5 Corvettes, and it can usually be traced to what are known as cold solder joints in the climate-control module. In this column, we'll show you an easy, no-cost way to repair them.
The term cold solder joint refers to a solder connection that was either heated insufficiently or cooled too quickly during manufacturing. A cold solder joint can also develop when component pins are moved before the solder has a chance to solidify. Additional causes include vibration over time, as well as deterioration resulting from repeated thermal cycles.
The hardest part of this job is removing the climate-control module from the vehicle. Note that if you have a convertible, you'll need to remove the console "waterfall" before getting started.
Start by removing the console. Gently remove the trim plate and all of the wiring connections. Loosen the attaching hardware, then lift the back of the console to clear the rear studs. Next, slide the console back to clear it from the front studs. (The front of the unit is slotted to allow it to slide all the way out.) If your vehicle is equipped with a manual transmission, remove the shifter boot. Don't forget to unplug the button inside the console that releases the fuel-cap door
Next, remove the instrument trim panel. This is the piece that runs from the console toward and around the air-conditioning and radio controls. Gently pry out the trim panel to the left of the ignition switch; then, remove the ashtray and the Torx screws. Gently pull up the panel at the bottom and remove the wiring connector. You should then be able to remove the panel.
You can now easily access the climate-control module by removing the two screws holding it in place and detaching the wiring connector in the back of the unit.
It's now time to locate the offending repair cold solder joints. Use a light and a magnifying glass to examine the various components' pins for hairline cracks in the solder surrounding them. (When in doubt, solder any suspicious connections.)
For repairs, you'll want to use a low-wattage, pencil-style soldering iron and rosin-core solder, both of which can found at Radio Shack or any auto-parts store. Start by applying a small amount of solder to the heated iron. Use the tip of the iron to heat the joint and apply the solder at the same time: The solder will flow evenly on the joint, repairing the connection.
Note that the soldering process should only take a second or two. Too much heat can damage the circuit board and surrounding components.
After the repairs have been made, reinstall the module and reattach the wiring. Turn the ignition to the on position and verify that the appropriate climate-control lights illuminate. If they do, follow the steps in reverse order to put everything back together. Otherwise, reexamine the module for additional cold solder joints.
Repairing cold solder joints can remedy many of your Corvette's intermittent electrical problems. They are commonly found in the remote keyless entry fob, as well as in the ABS/TCS and seat-control modules.
Don't be afraid to try this simple repair yourself. You could end up saving yourself $300-400.
A Depressing Condition
Q: I need advice on an issue I've had since I bought my '08 Z06 with only 3,200 miles on it. At times I get a "Service Traction System" warning message, along with a fault code of P2138.
I have been told this is a gas-pedal-sensor issue. What do you think?
A: The Accelerator Pedal Position (APP) sensor is, in fact, the most common cause of a P2138 code on these cars. There is even a Technical Service Bulletin (TSB) for this issue, 07-06-04-019C. Unfortunately, the entire pedal unit will need to be replaced, because the APP sensor is integrated into the assembly.
The APP monitors throttle inputs using an internal variable resistor, then sends these inputs to the engine controller. Think of it as being a bit like a dimmer switch in your home: As you move the switch, it allows more or less voltage to travel to the light.
Considering the mileage on your vehicle, I believe the APP pedal assembly is the most likely source of your problem.
Q: I own an '84 Corvette that has been plagued with problems. I do my own repairs, mostly because there always seems to be something that needs attention.
I am currently having a problem with a rough/erratic idle, the cause of which I've been unable to locate. Can you help?
A: The most common cause of an erratic idle that occurs at both high and low rpm is a vacuum leak. On '84 models, a leak often results when the top plate bolts on the intake manifold become loose. One or both of the throttle bodies' shaft bushings may also become worn and leak vacuum.
Another item that can cause a rough idle is a faulty coolant-temperature (CT) sensor. (It's located in the front of the Cross-Fire intake manifold, with a small plastic shield around it.) It may be possible to diagnose this by using a scanner to monitor the coolant-sensor temperature in the data-display section. You want the number displayed on the scanner to match the actual temperature of the coolant. If it doesn't, a faulty CT sensor is the most likely culprit.
As an aside, I love to see Corvette enthusiasts working on their own vehicles. It's people like you who truly keep the hobby alive.