I had one in 1982..here's a hyperlink for a sales brochure on Ebay http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=34228&viewitem=&item=270096551493&_trksid=p3907.m29
I was looking at the 1999 Mercury Cougar Owner Guide and it does not show that it has a gas cap warning light
it looks like a little orange engine in lower left on dash
There is a diagram inside the fuse box and also one in the owners manual if you have it.
Very few cars have a low coolant light but will have a overheating light. You can be sure it will look like water or a thermometer. Why not just raise the hood and check the coolant level.
follow the raditor hose it will have to bolts look for the bolts take them off and it inside the hose.
Look at the lower rear end of engine - follow cable from starter solenoid
cougar 1989 no lighting in dash instruments or speedometer. Where do I look for an open circuit. Fuses all checked good.
Take a look under the left drivers side dash, it may be there, I have a 1991 Cougar and that's where they hid mine.
it is black and on the drivers side front of the motor it is aluminum looking under the cap
Look either in the kick panels or the driver's side trunk panel
look inside the glove box on the door itself..most cougs have em right there
As of February 14 , 2013 you can still view the 1996 Mercury Cougar owners manual online at : www . motorcraft service . com ( no spaces ) Click on Owner Guides ( the fuse section starts on page 269 , it has the diagrams and lists )