【Used Jimny DIY】A critical situation where the tail lamp isn’t lighting! Attempted self-maintenance while investigating the cause!

The author, who purchased an old model Jimny and customized it for about 800,000 yen, received a notice one day that the stop lamp and reverse lamp were out. Immediately, I removed the cover for inspection and discovered the previous owner's odd handling. I researched why it happened and tried to find the cause.

Maintenance started!

The likely cause is either a blown bulb or a bad connection, so I first checked if the bulb was blown. The result was that only the left stop lamp was not lit, while the reverse lamp was on.

The maintenance methods are either replacing the bulb or cleaning the bulb contacts to improve the connection. When I removed the cover to take a look, it seemed that the part of the stop lamp that wasn't lighting had a blown bulb. The bulb contacts were also discolored white, so I decided to remove all the bulbs and check the condition of the contacts.

When I checked the right side, the bulb was not blown, but the stop lamp contacts were blackened, and the reverse lamp had something resembling red rust attached to it. Also, the adhesive painted near the reverse lamp seemed to be something the previous owner applied. I decided to clean the contacts, including this one.

For this maintenance, I purchased a 12V21/5W bulb and #400 waterproof sandpaper. I checked the compatibility table from the bulb manufacturer to find out which bulb to buy.

Since replacing the bulb is straightforward, I just needed to thoroughly clean the contacts with the sandpaper. I couldn't tell if the dot at the back was the contact or if the surrounding area was also a contact, but I worked to ensure that the accessible parts were cleaned. When I inserted the bulb and turned it on for verification, the severely corroded reverse lamp did not light up anymore.

It seems that the contacts have a mechanism where they move back and forth using springs, and the corroded reverse lamp appears to have trouble moving out to make contact with the bulb. There was no way around this, so I cleaned the corroded area to ensure it wouldn’t get stuck.

The replacement was completed. The stop lamp is significantly brighter, and the reverse lamp seems to have better connectivity, lighting up steadily. One thing I questioned during the inspection was why there was variability in condition despite being in the same environment. Upon research, it seems that much of the corrosion on the contacts is caused by an "oxidation film," which hinders electrical flow.

Various factors contribute to this issue, but it appears more likely to occur with low voltage input. As indicated, the contacts for the turn signals were clean on both sides, while the stop lamp, which lights up more often, had a lot of buildup.

However, regarding the right reverse lamp, it was clearly rust, which seems to have been caused by gaps created by the applied adhesive and water being more likely to infiltrate through the adhesive. It appears rust may occur on other Jimnys as well, so there may be structural issues or degradation of the cover. For this instance, I removed the adhesive in an effort to improve the situation.

Through this repair, my knowledge about cars has expanded further. Moving forward, I want to make sure not to miss daily inspections.

Interview/Article by Kazuma Tanaka

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