1995 Peterbilt 379 Blinker Problems

@wore out

 

Look behind the fuse box they are sorta bad to corrode

 

Touching the test light would be providing a ground , so . . . wait.

Any LED’s or a mis match of LED and incandescent bulbs in the flasher circuit?

I had a problem right side only, wound up being chafed power to rear aftermarket mud flap light bracket.

Check any non factory wiring first.

 

If they are all led even if you have the special LED flasher try putting 1 regular light in it somewhere. Especially if you were using a non LED test light.

I’ve got 3 of those trucks. My favorite one your gonna have 1 non led light in the blinker circuit somewhere or they ain’t gonna flash

 

If you’ve got the rear light boxes - mudflap holders and center pieces, pull all that wiring out and check for a chafe.

Is it an intermittent problem?