Sorry for the delay in replying regarding this issue. I was unable to find the info I had seen earlier until I accidentally stumbled across it while looking into another issue.
“The primary disadvantages of WAGO connectors in automotive environments include:
- Lack of Environmental Sealing: Standard WAGO 221 connectors are IP20 rated, meaning they are not sealed against moisture, dust, or road salt. In an engine bay or under-chassis environment, this leads to rapid corrosion of the copper busbar and the wire strands.
- Vibration Susceptibility: While they perform well in static residential settings, some users report that high-frequency vibration in vehicles can cause the lever-actuated spring clamps to loosen over time.
- Accidental Disconnection: The lever mechanism can be accidentally released when pushed into tight spaces, such as behind a dashboard or into a wiring harness bundle.
- Bulkiness: Compared to a properly soldered and heat-shrinked splice, WAGOs are bulky and can create "lumps" in a wiring harness that are difficult to conceal or manage, leading to further strain on the connection.
- Not Ideal for Fine Stranded Wire: While WAGO claims compatibility, some specialized automotive electrical technicians argue that fine-stranded, low-gauge automotive wire does not get as reliable a connection as solid or coarse-stranded wire, potentially leading to increased resistance.”