I've noticed that at night my key fob does not work unless I'm a foot from the door. This happens only at night. I'm thinking it is my motion activated light on the outside of my garage (I keep the truck in the driveway). I do not have this issue during the day, only at night. Anyone else have this issue? I think it has to be that because I can't think of any other reason and I've actually come across something like this before when I used to install satellite and certain tv screens would block the remotes IR if the receiver was put under the tv. I know the key fob isn't IR but I think the same concept applies here.

 

What year is your truck? Is this the factory system?

I've never heard of that exact issue. Maybe this is a known issue @raysorenson may be aware of? But it honestly sounds like pure coincidence to me.

 

It's a 2002. I thought it was coincidence at first as well, but over time I noticed it would literally only happen at night. There is literally nothing else that I can think of in my area that would cause that other then the motion light above the garage.

 

Is it only when the light is on?

 

Are you able to unpower the light fixture tonight and see if the action repeats with the fixture unpowered? It may be something unrelated to the light but both related to night.
Is it the Ford remote? Aftermarket? It should have an FCC number on it and if aftermarket that number would help.

 

Your keyless entry system is RF and light or lack there of doesn’t affect it. I’m an automotive locksmith and can tell you over 90% of keyless entry issues that we deal with are battery related. Change the battery/batteries in your fob if you haven’t.

 

Yes to all you said.
But if range is good in day and poor only at night, well batteries do not know day from night. The remote may have poor range all the time.
Compact fluorescent lamps with poor shielding (or poor design) give off RF but that is usually in the HF range, not VHF.
Who knows, Someone could be firing up an ungrounded arc lamp for their pot plants. Could be a unscrupulous ham with an overpowered transmitter. Either of these would cause interference across much of the spectrum.
But to find the actual interference we should know the freq. of the remotes.
315 or 433 is the normal for ford but if the remote is aftermarket it could be on 900 and that range is full of poorly designed crap that could interfere.

edit: Another source of possible night interference would be near "Clear-Channel" AM stations. The night interference from these is only 1/4 mile at most but if an AM transmitter is near it could certainly cause problems.

 

It's a factory ford fob. I have 2 of them and both act the same at night only. The range in the day is great, but at night it's literally either 1 foot away or right next to the window. On the back of the fobs it says : Ford Motor Company 2L3T-15K601 - AA FCC ID CWTWB1U331 CAN 1786 104 575.
It's not the batteries b/c I've changed those out to no effect. I also cannot turn off that light, there is no switch, it's just directly wired in to some breaker I'm sure. I suppose I could flip that breaker if I can find it. It only happens at my house tho, not anywhere else when it's night. I suppose I should have mentioned that but I didn't think of it.

 

Find the breaker and relieve the mystery. It's the only way you'll know for sure if you're suspicion is correct.

 

Please power off the lamp fixture and see if range increases.
Looked up the FCC # and application data. Alps Electric of Osaki Japan. 315 Mhz and very, very low power output. This thing barely whispers. That does make the batteries last longer though.
The max range of the transmitter is 3 meters, You are only getting 1 foot of range so that is a fail. Do you get 3m in the day? I have the same remote and barely get 3m with fresh batteries. I always get 2m or more though.
I feel something is bleeding over your frequency only at night.
I looked at all the other things in that frequency range that would be in a household that would normally be active at night (this eliminates things like TPMS and garage door openers) and found that many wireless alarm systems use this frequency with a higher power to communicate with remote devices.
There were thousands of licenses in the range and I got tired of looking over them. Most were of types that would be of very short transmissions like garage remotes. But some were of types that had higher power and longer transmission times, like handheld scanners, barcode readers, etc. The only one I saw that made sense to relate to night was alarm systems with remote device monitoring.

And like I posted above, there are several items that if not operating properly could cause wide spectrum interference.
The way to find it is with a spectrum analyzer (expensive unless you know someone who has one) or to turn off items while the phenomena is occurring and see when a change happens.