After the first rain here in 9 months or so (but it was a 3.5" rain, which is a lot for here), I noticed a lot of moisture in the driver's side headlight on my 2014 MDX. The passenger side headlight was clear. I waited for it to just clear but it didn't even after a week or two, even during a very dry (< 10% humidity) sunny and hot (upper 80s) spell.
One of the first things I did was to check on this forum to see if anyone else has run into the issue. The only thing I could find were a few posts early on, back in 2014 or so, where some people ran into this, curiously only on the driver's side headlight, but they were under warranty so they took it to the dealer, who replaced the headlight unit. My MDX is out of warranty now and these headlights are ridiculously expensive so I wanted to fix the condition rather than replace the headlight.
I was considering removing the turn signal bulb to be able to open the area to the air for the moisture to escape but upon inspecting the area I found that there's an access port to the headlight housing. I played with it and found that the cover for it is easily removed by twisting it off. This is a plastic cover with an O-ring on it.
I opened that port cover, parked the vehicle so the sunlight was hitting the headlight under the theory it would heat up the inside of the housing and with the port open the moisture could evaporate out of it. I left it like this for a couple of hours and sure enough, the moisture evaporated. I then put the port cover back on and all has been well since then.
We haven't had another real rain yet (that was the only rain in 9 months or so other than one time with a 'trace' of rain) but so far it's still clear. The cost for this fix was $0, which is about what I usually like to pay. The procedure is very easy and no technical knowledge is required. The following are the steps I followed but one might be able to skip taking off the plastic cover and housing if they can snake their arm in there. It's easy enough to just remove the cover/housing so I did.
1. Remove the front engine cover piece, the one over the radiator and whole front of the engine bay, by just popping it off with your hands.
2. Remove the air intake plastic housing, i.e. the one that sort of is over the battery, by removing the 2 plastic clips that secure it to the vehicle.
3. There's now ready access to the headlight housing port. On the back of the headlight housing is a round port cover about 2.5" in diameter that has some tabs on it to permit twisting it off. Reach your hand in there and twist it counter-clockwise to pop it loose from the housing and then let it rest there such that there's now a big gap to allow air into and out of the headlight housing.
4. Park the vehicle so the sunlight hits the headlight. This'll heat up the air inside the housing and eventually dry out the inside of the headlight. When it's dry, put the port cover back on, the intake housing back on, the engine cover back on, and you're done.
Whenever it actually rains here again I'll see how the headlight's doing moisture wise and if it still has an issue I'll probably see if I can do something more about that problem by lubing the O-ring on the port cover or looking for any other way moisture is getting in but not out, but in the meantime the headlight's fine now.
The attached pics show the headlight with a bunch of moisture in it, the headlight housing port I referred to in its closed position (the piece with the plastic tabs on it that are above the bolt in the pic), the port in the opened and not attached position, and then the dried out headlight.
I hope this helps any of you who run into a similar issue.
One of the first things I did was to check on this forum to see if anyone else has run into the issue. The only thing I could find were a few posts early on, back in 2014 or so, where some people ran into this, curiously only on the driver's side headlight, but they were under warranty so they took it to the dealer, who replaced the headlight unit. My MDX is out of warranty now and these headlights are ridiculously expensive so I wanted to fix the condition rather than replace the headlight.
I was considering removing the turn signal bulb to be able to open the area to the air for the moisture to escape but upon inspecting the area I found that there's an access port to the headlight housing. I played with it and found that the cover for it is easily removed by twisting it off. This is a plastic cover with an O-ring on it.
I opened that port cover, parked the vehicle so the sunlight was hitting the headlight under the theory it would heat up the inside of the housing and with the port open the moisture could evaporate out of it. I left it like this for a couple of hours and sure enough, the moisture evaporated. I then put the port cover back on and all has been well since then.
We haven't had another real rain yet (that was the only rain in 9 months or so other than one time with a 'trace' of rain) but so far it's still clear. The cost for this fix was $0, which is about what I usually like to pay. The procedure is very easy and no technical knowledge is required. The following are the steps I followed but one might be able to skip taking off the plastic cover and housing if they can snake their arm in there. It's easy enough to just remove the cover/housing so I did.
1. Remove the front engine cover piece, the one over the radiator and whole front of the engine bay, by just popping it off with your hands.
2. Remove the air intake plastic housing, i.e. the one that sort of is over the battery, by removing the 2 plastic clips that secure it to the vehicle.
3. There's now ready access to the headlight housing port. On the back of the headlight housing is a round port cover about 2.5" in diameter that has some tabs on it to permit twisting it off. Reach your hand in there and twist it counter-clockwise to pop it loose from the housing and then let it rest there such that there's now a big gap to allow air into and out of the headlight housing.
4. Park the vehicle so the sunlight hits the headlight. This'll heat up the air inside the housing and eventually dry out the inside of the headlight. When it's dry, put the port cover back on, the intake housing back on, the engine cover back on, and you're done.
Whenever it actually rains here again I'll see how the headlight's doing moisture wise and if it still has an issue I'll probably see if I can do something more about that problem by lubing the O-ring on the port cover or looking for any other way moisture is getting in but not out, but in the meantime the headlight's fine now.
The attached pics show the headlight with a bunch of moisture in it, the headlight housing port I referred to in its closed position (the piece with the plastic tabs on it that are above the bolt in the pic), the port in the opened and not attached position, and then the dried out headlight.
I hope this helps any of you who run into a similar issue.
