1999 Dodge Ram 1500 pu. the inside of the headlight housing (psgr side) has water vapor forming on the lense. I can't figure out how to remove that assembly to search for the leak. Any help?

sounds like the vavle is bad

I replaced fuel filter 1992 Dodge Ram W150 4wd 5.2 engine...located inside frame rail psgr side just fwd of rear wheel. mounted 1/2 in. bolt.

On the upper grill side of the headlight assy. there
should be 1 or 2 push pins that hold the seal on the
headlight assy to the front of the fender. Also check
for a guide/push pin on the inner top of the assy on
the outer fender side. That should be all there is to
hold the headlight in place. Hope this helps.

I hope describes correctly the detail procedures for replacing 2009 Dodge RAM 1500 Headlight Bulb.

- First, open the hood; Disconnect the negative battery cable;
- Remove the four grille attachment bolts;
- Remove the grille;
- Remove the two headlamp assembly attachment bolts;
- Then reach into the front wheel house ahead of the front wheel to unsnap and lift the cover over the access hole in the front of the wheel house splash shield.
- Access to the bulb retainer can be gained through the wheel liner hole (see picture).



After that reach through the access hole to access the rear lamp retainer and remove headlamp assembly (see below picture).



Disconnect electrical connectors, and replace the bulbs.

Good luck (remember rated this help).

If you are replacing the headlight bulbs, rotate the bulb retaining lock ring counter-clockwise, pull retainer out of headlight housing and disconnect electrical connector. On the drivers side, you have to remove the fuse and relay box screws and move the box to the side to access the headlight bulb. If you are replacing the headlight housings, there is a push pin and 2 screws on the inside, behind the hood and one screw on the outside at the bottom. Remove these and pull the housing out enough to remove the bulb retainers.

Did you take a voltage reading at socket of dim one compared to bright one?

I believe there is a couple of screws under hood at housing, maybe down the side, and a plug inside fender, in front of wheel that you turn & pull out, to undo fastener at rear of housing, then pull housing right out to change it.

Here's a link to a pdf file containing the headlight wiring diagram for your year model Dodge Ram 1500..
I can't help but notice that you say you've replaced the headlight relay? That's quite odd, because there is NO headlight relay on this vehicle- only a 40 amp fuse located in the power distribution box that sits behind the battery inside the engine bay.
The switch is notorious for burning out because there is NO RELAY on this vehicle, and there is a recall (#819) but this only affects 3500 models even though the headlight wiring is the same for 1500,2500 and 3500 model Rams.
Here are two more links that will help you troubleshoot your headlights problems.
HereInformation on Putting a Relay in the Wiring System

There should be two screws on the inside edge of the assembly, one next to top lense and one next to bottom lense. This removes entire assembly not just cover. these are sealed units.