I am working on the same problem. However, I do know it is located on the left side of the engine compartment when looking forward from the drivers seat. A small black, plastic housing covers it. Tom
headlight relay location on a 2004 mercury grand marquis
The 1999 Mercury Grand Marquis air suspension relay switch can be found on the firewall in the engine compartment. The air suspension relay switch will be on the passenger side of the firewall.
how to remove right turn signal relay on 1986 mercury grand marquis
The relay for a 99 Grand Marquis heater is located on the kick panel on the driver's side of the car. The relay is located under the kick panel cover.
Inside the front right and left fenders, just under the side marker light, I believe. If it doesn't work at all, check the relay first.
The relay is located in the engine compartment to the right of the heater hoses if you are looking at them. It dose not look like a regular rely. It has a connector that plugs into it.
It should be located in the Trunk near the right side. If it's not there, it's probably located under the hood with the other relays. hth
Replace the flasher relay if none of them are working.
it is on the firewall and difficult but not impossible to get to and replace.
blower relay located on the engine compartment by the firewall
On a 1998 Mercury Grand Marquis : In the fuse panel under the dash : ( # 16 is a 20 amp fuse for the cigarette lighter and emergency flasher relay )
the black box on the left side of the trunk