Front left turn signal dies in warm weather

1993 Ford Explorer XLT with 230,000. Left front turn signal doesn’t work in warm weather–above 60 degrees F. Cold weather it works fine. One other effect in warm weather is that the dashboard indicator for the turn signal does not light up. I’ve confirmed that the left rear lamp works normally. I can hear the clicka-clicka of the flasher. I’ve replaced the bulb. No fixy. I put a multimeter on the socket and I get a weak signal when the turn signal is on–just not enough signal to light the lamp. I asked a friend about this and he said to get rid of the junker. I jiggled all the relevant cables I could find, but still no fixy. Can anyone help?

Do the emergency flashers work normally when the turn sig is whacked?

if so the multi function switch is probably the problem

If Ranger’s idea does not work, start working back from light carefully cleaning every connection (including the one to the bulb) you find.

Front left doesn’t work when emergency flashers are on. Left rear works.

There is a high resistance in the path to the light that is causing the trouble. I would try disconnecting any connectors you can find in the cabling running back to the firewall and under the dash tieing to that light and then reconnect them. That may solve the trouble. The trouble may also be in the flasher unit itself so if the connector trick doesn’t work you might try replacing it.