Code 67 NPS Circuit Failure

[Marccus]

I'm getting a code 67 which states that there is NPS (neutral pressure switch) circuit failure.

What is the NPS and what system does it correspond to?

Does it have anything to do with the A/C pressure switch?

My A/C was running fine, then stopped working. The clutch won't kick in. The compressor, suction piping, discharge piping and all o-rings are new.

I thought maybe there was a refrigerant leak and the pressure was too low for the compressor to kick in.

I tried to add new refrigerant to the suction side from a can, but none would go in which indicates that the refrigerant charge is not low and there is no leak.

I am going to do a UV dye leak test and check pressures with a manifold gauge set.

But I would like know if this NPS switch is the problem if it is related to the A/C.

I have replaced the A/C pressure switch on the accumulator just about a year ago, so it would be hard to believe this would be the problem.

If the NPS is not the A/C pressure switch is there a error code for the failure of the A/C pressure switch?

 

[projectSHO89]

DTC 67 on an EEC-IV vehicle is usually caused by failing to turn the HVAC or EATC to OFF as the directions say to do.

Turn the AC to OFF and re-run the test.

Alternatively, the same code may be caused by the clutch pedal switch reading the wrong state or, if an automatic, the shift lever is not in the correct position per test set-up.

From the 93 PCED:

TA1 DIAGNOSTIC TROUBLE CODE (DTC) 67/522, 525 or 528: SYSTEM IDENTIFICATION

DTC 67/522, 525, or 528 resulted from the voltage being high at either:

-- Pin 10 = A/C input

-- Pin 30 = PNP/CPP input

while cranking the engine or during KOEO Diagnostic Test Mode (DTM).

Possible causes:

-- A/C circuit shorted to power

-- CPP circuit open

-- PNP open

-- Damaged PCM

-- Starter relay disconnected during Self-Test.

For Manual Transmissions:
3.0L SHO and 4.9L
GO to «TA7».

1.9L SFI, 2.3L, 3.0L, 3.8L SFI Super Charged, 4.0L and 5.0L SFI MAF
GO to «TA2».

For Automatic Transmissions:
1.9L SFI
GO to «TA10».

For all other engines:
GO to «TA8».

 

[llamaking122]

on another note when you put in refrigerant. jump the condenser iirc switch

 

[projectSHO89]

on another note when you put in refrigerant. jump the condenser iirc switch

Isn't necessary, but it will speed up the process.

 

[Marccus]

In other words, it's really not important. Probably left EATC A/C on.
Will run again.

 

[Marccus]

on another note when you put in refrigerant. jump the condenser iirc switch

What does this mean to "jump the condenser iirc switch"? How do I do this?

iirc acronym = _____________ ????

I can't add refrigerant, the suction side appears to be at too high a pressure when the clutch is not engaged and the compressor is not turning.

This to me says there is no leak.

Will your instructions allow the clutch to engage and the compressor to turn so suction is created and refrigerant will be drawn into the system?

Thanks.

New problem stated below.

 

[Marccus]

'89 SHO w/ around 450K? ... who cares at this point.

Ok. RIDDLE ME THIS.

When I turn the A/C on when idling, there is no drop in the rpm's and the clutch/compressor system doesn't engage and I blow warm air - makes sense.

Now I start out of 1st gear. Fine.

Now I engage 2nd gear, as I speed up in 2nd, the car starts to buck wildly, and I get a screeching sound (belt?) from the front passenger side of the vehicle. But it seems to come more the side than up front in the engine compartment. Power steering pump/pulley makes more sense for the noise to come from - didn't touch this pulley when installing compressor/piping etc.

If I back off the throttle and cruise while engaged in second, the bucking seems to subside.

Now it seems that the air is blowing a little colder but I can't be sure; certainly not blowing A/C cold air. If I turn the A/C off, all this behavior stops and the car runs fine.

Now when I stop to pull over (didn't turn off the A/C during this run), I check the air coming from the vents and it doesn't seem to be as cool as before (damn!). When I pop the hood, the clutch is not engaged. Perhaps it was when I was driving and unfortunately, it just happened to disengage when I stopped. (Damn!).

Anyway, car runs fine in idle when stopped whether the A/C is on or off.

It's unfortunate that someone can't sit in the engine compartment or have a video on the compressor clutch to see if it is engaged when the bucking starts. (I could break out my anti-government spy equipment :theyareontome:

The only logical conclusion is that it must be for this bucking to occur?

And a screeching belt would indicate a belt too loose. Correct.

Unless anyone has any other things to try, I'll just tighten the belt and see what happens.

No screeching of the belt occurs when I start the car - typical when you R&R the alternator and don't tighten the belt properly, so I never thought of adjusting it.

BTW, there are belt tightening tensioners that are made, anyone try one?

I've hear that they are pretty useless (except the ridiculously priced exotic ones) and tightening by feel is the best way to go.

Thanks.