Diagnosing and troubleshooting problems with a VW Beetle is relatively straightforward. If you have basic repair knowledge and a set of common shop tools, you should be on your way in no time. Most troubleshooting involves starting or electrical problems. Other problems occur when driving or braking. While this is not an exhaustive list of diagnoses or solutions, these are general troubleshooting procedures to help you handle some of the most common problems you might experience with your Beetle.
Check for fuel in the gas tank. Check the gas gauge reading and fill if empty. A full tank and an empty reading indicates a broken fuel gauge sender. If this is the case, remove and replace following the manufacturer's instructions.
Turn the ignition key but do not start the car. Verify operation of oil and generator indicator lights. Open the rear deck lid. Check for spark by removing one spark plug wire and plugging in a spare spark plug. Have a helper turn the ignition to crank for a moment as you hold the spark plug 1/4-inch or less from bare metal. The colour of the spark determines the condition of your ignition: blue or white is best and yellow is weak, and includes problems with plugs, wire, points or coil. Remove and check each of these parts and replace as needed.
Check for fuel flow by starting the engine and looking at the transparent fuel filter. The fuel pump visibly draws fuel through the filter if it is working properly. Remove and replace the filter if it is dirty or clogged. Blow air into the supply end to verify an unblocked fuel line. Beetle models equipped with a carburettor may occasionally suffer from a stuck fuel float. Give the carburettor a light knock with the handle of a screwdriver to free it.
Remove a spark plug with a plug socket and wrench to check for compression. Insert the compression tester in place of the spark plug. Have a friend crank the engine a few times. Note the compression and replace the spark plug. Repeat this step at all spark plugs. Uneven, high or low compression indicate a problem with the condition of the upper engine, including heads, rings or pistons. No compression indicates a broken piston or rod.
Verify the battery electrical connections are secure. Use the voltmeter to verify six or 12 volts, depending on the battery. Use the jump leads to jump-start the battery if necessary. Replace the battery if it cannot be charged. Test the ground connection by using the resistance setting of the voltmeter between the negative terminal at the battery and the bare chassis. Remove the ground strap and use a file to clean the strap where it connects to the chassis. Use a wire brush or sandpaper to clean the chassis where it connects to the strap and reinstall it.
Inspect all wires visually for loose or broken wire or connections. Splice in new sections of wire of matching size at any frayed wire and wrap with heat shrink tubing or electrical tape. Replace broken push connectors.
Verify 12 volts at the starter switch, all fuse terminals, the ignition coil and the carburettor solenoid if equipped.
Inspect the fuse box and replace burnt fuses. Remove and lightly sand all other fuses to ensure consistent electrical contact. Reinstall the sanded fuses.
Turn the light switch to driveway setting if equipped. Inspect driveway lamps at headlights and taillights for operation and remove and replace if needed. Turn the light switch to the headlight setting, inspect sealed beams and replace if needed. Switch the headlamps to bright setting and replace if needed. Check interior lighting at all settings and replace if needed. Test the brake lamps, indicators, reverse lamps and hazard flashers and replace as needed.
Test the air pressure of the tires with an air pressure gauge. Adjust tire air pressure as recommended in the owner's manual. Inspect the treads for damage and replace immediately with the spare tire if any is found. Use the tire wrench to check that all lug nuts are firmly tightened. Pull emergency brake lever to test its operation prior to driving. Drive the car slowly and test the brakes.
Raise the front of the vehicle with a jack and rotate the front wheels by hand, listening for rumbling. Push and pull on the wheels by hand to determine if the front bearing is worn. Replace the bearing if the bearing rumbles or moves significantly. Rotate the front wheels by hand to test for resistance. Remove the wheels to adjust or replace the brake shoes if there is significant resistance or squealing. Rotate the wheel and listen for a light knocking sound. If you hear any sounds, take the vehicle to a shop for repair. Repeat the steps for all four wheels. Visually inspect underneath the front end for worn or broken rubber covers on the steering components. Fill tie rod ends and steering components with grease.
Start the engine and drive the car. Listen carefully for knocks from the motor, suspension, wheels or brakes. At idle, only the engine should be heard. Thumping from the tires while driving indicates wheel or suspension problems. Vibration from the indicates unbalanced or damaged wheels. Take the wheel to a mechanic for repair or balancing.
Depress the brake pedal and release while the vehicle is at a complete stop. If the brake pedal does not return to the original position, or is squishy, tow the car immediately to the shop for brake work. At speed, feel for pulsation in the pedal or steering wheel when applying the brakes to determine front or rear brake problems.
Check for operation of all gears in normal sequence. Feel for hard shifts or knocks which indicate shifter or linkage trouble. Missing or popped gears indicate transmission problems that a transmission specialist may be able to diagnose further.
Slowly turn the spark plugs during removal or replacement to prevent thread damage.
Gasoline is flammable and volatile. Gas evaporates quickly and vapours may ignite. Have a fire extinguisher handy. Keep loose hair and clothing away from moving parts. Use wheel chocks according to the manufacturer's instructions whenever raising or lowering a car with a jack.