2002 F150 2wd regular cab 4.2 with 199,000 miles so far.

Two issues.

1. The Air bag light blinks and/or remains on. The OFF position light for the passenger air bag is OUT(not illuminated) while in locked off position.

2. Check oil level light illuminates periodically and then the AC will cut off too (no cold air).

I know that the truck has oil pressure because there is a real oil pressure gauge installed.

Is the oil pressure sensor and AC control related electrically - as in body computer or GEM.


Are all three systems connected somehow?

 

1. Count the flashes to decipher the two-digit fault code. Post that code.
2. Is the engine trying to stall when that occurs? Any other symptoms?

I know of no connection between the oil pressure idiot switch and that the operation of the A/C clutch. However, the state of the oil pressure switch IS available to the microprocessor in the cluster and the cluster communicates with the PCM and the PCM does have the control over whether or not the clutch relay gets energized, so there is a plausible path for it to happen. I've just never seen it, heard of, or have found any such reference in the factory service manual. I do know that on newer NBS F150s, at least, a severe misfire will disable the compressor and i could never find that in the factory manual.

This hypothesis is easy enough to test. Simply locate the pressure switch, it's above the oil filter on the 4.2L. With the engine running, normal oil pressure indication, A/C on and operating, disconnect the switch. The light should come on in the dash and you'll see what happens to the A/C compressor operation. Let us know.

 

Last night I noticed that the engine coolant gauge was registering HOT, but the truck was running fine.

This morning I did some looking around and I may have a small leak at the water pump. It was raining earlier so I could not tell if there were any water drips

from the pump on the ground.

Anyway, I added about 1/2 a gallon of coolant in the tank and I took a rather long drive to see what happens.

So far it looks good.

I never noticed the HOT coolant gauge until last night. I wonder if the truck was going in to a "LIMP" mode by shutting off the AC compressor?

Coolant is running in the NORMAL range now and the airbag "OFF" light is illuminated now(at least for now).


Do you think the FORD engineers placed the flashing AIRBAG light near the TEMP gauge for a reason? Yet I never bothered to look AT the temp gauge at all?

I drove the truck pretty hard on the way home to get a catastrophic failure, but the truck is holding together so far.


Iʻll keep everyone posted.

This is one tough truck.

 

Except it's not. There are two additional lamps in between them. They had to put it somewhere.

The idiot light above the fuel gauge, if you look at your owner's manual, is a dual-purpose idiot light both for temp and oil pressure.

That is likely. If the PCM was detecting over-temp condition, reducing the load on the system by cutting the compressor would be a logical engineer's choice.

It sounds like you have an intermittently open circuit for that bulb. Next time the SRS lamp flashes, you'll likely end up with an LFC 27.