I bought an 08 f150 a couple months ago and recently when I’ve been trying to accelerate last 60 everything on the interior goes out but I can still use the gas and brake.

 

Explain 'Everything on the interior goes out"
you mean "past" 60?
Meaning the truck vibrates so bad the cluster goes blank?
Does the radio quit too?
If so, check rear driveline U - joints and yoke for the vibration, and maybe replace your ignition switch if the plastic is getting loose from the metal

 

Reminds me of when the alternator went out on a truck I had in the past. Probably not the problem for yours though if it keeps running. Still, might be useful to get a free battery and alternator test at an auto parts store.

Have you tried adjusting or tapping on the dimmer switch when it happens? How about banging on the top of the instrument panel? Any dash warning lights on?

 

That is what I was thinking
A bad cluster connection or battery connection maybe even at the fuse panel or the ignition switch

 

For example I just want to accelerate past anything and if I go fast enough I guess the dash goes out the radio and ac turn off. Then a couple seconds later everything comes back and the check engine light is on blinking and the truck shakes for the duration of the check engine light blinking

 

Flashing check engine light is a serious misfire. Continuing to drive it like that can lead to serious engine damage.

 

I did think it was the alternator at first but I tested it disconnected the battery terminals while the truck was on and it was still going smoothly. The dimmer switch would it be the scroll looking type thing that adjusts the lights when it’s night? If so no I haven’t tried. Yes I have the check engine light on for my tire pressure and for the brake. I had it tested for the check engine light at autozone and it’s like saying spark plugs, low volt connection, the maf sensor and the o2 sensor

 

Your dimmer switch is on the turn signal stock, just pull it back for high beams and pull back again for low beams
That rotating **** is the rheostat for the dash illumination (dims and brightens the dash only)

 

I also thought it was something with the battery when I had it tested at autozone it came out as good. I thought it was the battery cause when I tightened the terminals after checking the alternator one terminal was loose and I tightened it and when I took it to drive the check engine light had been gone and the truck was driving good but it had started a couple days later doing the same thing:/

 

• Since tightening it worked for a while, did it get loose again? The cables should be tight enough that you cannot twist them.
• Also are both the battery posts and the inside of the cable connectors clean?