I was able to fix some stubborn issues with two red battery cars with the following tricks. And without ripping things apart.
Step 1: Identify battery car as the problem. Check that all batteries have power. Check that cables between engine and battery car have connection and plugs are clean. Check that your motor is not dead.
Step 2: Check battery & cable connections. Clean all metal parts which connect with batteries and cable sockets.
Step 3: Check circuits. Check that battery car base’s circuits are ok. When the main switch is to the left, you should have connection from the left socket (a) to the left battery connector (b) and from the right socket (c) to the right battery connector (d). If the main switch is to the right, you should have connection with the left socket to right battery connector and from right socket to left battery connector.
Step 4: Check roof connections. If you have ok circuits on the base, but you can't get current out of the battery wagon, problem is with the roof. Remove dirt & corrosion from metal parts both inside the roof and on the top side of the battery car. Check that no metal parts are missing and they connect with the metal strip on the top side of the battery car.
Step 5: Check semaphore disconnecting switch. Check that circuit is closed between points (e) and (f). The red button under the battery car should move freely up and down and you should feel slight pressure when pressing the button. The circuit opens when you press the button and closes when you release it. Make sure that the connection is clean and metal touches metal. Spray the connection with cleaner and use finger to move part (f) gently sideways to rub the connection clean. If it does not help, use small patch of fine sanding paper (1000) to clean the metal surfaces, just few passes is sufficient. If the moving metal strip on the bottom of the battery car (f) is bent upwards, bend it slightly back down to add pressure to the connection. Make sure the red button still works & cuts the circuit when pressed.
Step 6: Check main switch connections for corrosion. If you have eliminated all the problems described above, the issue is with the main switch connections. They can get corroded or bent. First clean connections with CRC Oxide Clean & Protect Pro or similar cleaner. Scrape gently the long metal strips on sides & center with a cotton swab, scalpel or other suitable metal tool, if necessary. You need to get your cleaning product also inside the switch, as the problem may be with the connections under the switch. Move the switch several times back and forth to clean the contacts.
Step 7: Fix bent main switch connectors. If the battery car still does not work, the likely culprit is bent main switch contacts.
Check connections with a multimeter:
Turn the main switch to the right and check that:
- (h) is in contact with (j)
- (h) is in contact with (l)
- (g) is in contact with (k)
- (g) is in contact with (i)
Then turn the main switch to the left and check that:
- (h) is in contact with (j)
- (h) is in contact with (k)
- (g) is in contact with (i)
- (g) is in contact with (l)
Small metal strips (g) and (h) are bent under the plastic switch in L shapes towards the centre of the switch and towards outside. If for example main switch is turned right and there is no contact between (j) and (h), but there is contact between (h) and (l), this is means that the inner “L” does not touch the (j). And if there is no contact between (h) and (l), this means that the outer “L” does not touch the (l).
Go easy with the multimeter, you can get false results if you press hard and make the two disconnected metal strips meet.
Check which side of the switch is the issue. Only tamper with the contacts which do not work, leave the working connections alone, as it is easy to press them out of whack. On the right side (g) try to press down the metal strip on the switch or insert small plastic strip in between the plastic switch and the metal connector. On the left side (h) insert small plastic strip into the small slot on the bottom of the battery car (sliding it in between battery car bottom and the metal connector) and another in between the metal connector on the switch and the plastic switch. See drawing below. I used two plastic strips which were 0,3 mm thick and 3 mm wide.
