So this morning I left the house and my truck was running rough at idle and acceleration. Another observation was that the AC was blowing, but not cold and it was obvious that compressor was not on. About a mile later at a traffic light, the AC started blowing cold and the rough performance went away.

168K on the 5.0 clock, and no CEL when it did this. When I got back home, I connected ForScan and there was a DTC for PSCM specifically B1304. Nothing else.

So any thoughts as to what would cause the rough drive and no compressor, then it just dis appear?

 

Low coolant? Bad clutch on the AC unit? Just a couple of thoughts.

 

Ed, don’t you have the digital Helms for your F150?
a quick check on B1304 said
accessory relay problem
https://www.engine-codes.com/b1304_ford.html

might just have a set of stuck points or a bad solid state relay.

 

I do not, I have a Ford DVD for my year model. That is interesting because in Forscan it said this:

Code B1304-Electronic Power Assisted Steering System
Additional Fault Symptoms (-48):

Status (-48):
-Previously set DTC - not present at time of request
MIL is off for this DTC
Test not complete

Module: Power Steering Control Module
Freeze frame #1
PWR Mode Key : Accessory - Power mode key state
PWR MODE QF: Eval in progress - Power Mode Quality
SW ANGLE : -332.20 - Steering wheel angle

 

So episode number 2 today, came to a stop ac went warm but still blowing and the truck started to run rough. Took off from stop sign and about 15 seconds later AC started back cold and engine was smooth again.

When I got home, connected ForScan and no DTC's. Interesting find though. Within the PCM, there is a PID (i guess) and it is: BATT_VLO_ACC - Very Low Battery voltage disabling air conditioner operation. Interesting!

 

Maybe you got a battery that is going bad??? Or alternator?

 

Quite possible, 168K on the alt would not surprise me but I would think that would throw a code or a light? Regarding the battery, I tested it and it tested good at 755/850. I did the old test the fluid tester and it was good. But who knows! In Forscan it indicated 13.57.

 

I'll give you my thoughts but keep in mind I have no hands-on experience with Gen-12 F150s.

B1304 points to the Accessory Delay Relay. If I got the correct fuse panel for for your truck, that is Relay-49 in the Passenger Compartment Fuse Panel. Subtype 48 is a Supervision Software Failure. My guess is the the PSCM is seeing a exceptionally low voltage due to a relay sort to battery. The low voltage is causing the software issue and producing the code which it is blaming on the Accessory Delay Relay.

What might be happening is the relay shorts to battery soon after being energized, causing battery voltage to drop, resulting in all the electrical oddities you experience. Then after some time, the relay short circuit breaks, maybe due to heat in the relay, which raises the voltage back up to normal and everything starts working normal again.

My suggestion is to buy all new relays. Swap them out one at a time and test after each swap. Hopefully you find a bad relay. If the voltage is getting that low, the resulting DTC could be incorrect as well, after all, the DTC is a binary string and it only takes one error to broadcast an odd DTC.

If this makes any sense, post your results. I will monitor this thread. Good luck.

 

Thanks! Do you think I necessarily need Ford relays? WHich other relays?

 

Ford just buys their relays from OEMs like TE, Bosch, and others. As long as the aftermarket claims to be an exact replacement, I wouldn't worry about it.

The Passenger Compartment Fuse Panel only has the one relay, but there are several in the Power Distribution Box (underhood):

• Relay-1 = PCM
• Relay-2 = Starter
• Relay-3 = Blower Motor
• Relay-4 = Rear Window Defroster
• Relay-5 = Engine Cooling Fan High Speed
• Relay-7 = Run/Start
• Relay-8 = Fuel Pump
• Relay=10 = PCM (3.5L)
• Relay-23 = A/C Clutch
• Relay-37 = Trailer Tow Left Stop/Turn
• Relay-38 = Trailer Tow Right Stop/Turn
• Relay-40 = Engine Cooling Fan
• Relay-62 = Wiper Motor
• Relay-85 = Engine Cooling Fan Low Speed

You don't need to buy all new ones if you don't want to. Just buy a couple of each type. It looks like there is only 3-5 different types. Once You've swapped one out and it is not bad, you can re-install it and go on to the next one. You then have some spares if it is only one relay that is the problem. Don't rule out any of the relays. Who knows which one (if any) could be the problem.