On my 98 suburban the rear turn signal is out,I went to change it
And the bulb was still good but it had some yellow stuff on it look like putty
I put a new one in it and it still don't work.anyone no what that yellow stuff is
And why it don't work

 

The yellow stuff is most likely dielectric grease. You most likely need to replace the bulb board (sockets)

 

MDTAHOE is right, I just had to replace the board that has the bulb sockets in it on my 97 Tahoe.

 

Thank you guys for the information I change the bulb board and all the bulbs and
It works fine thank u