A/C gas indicator light

[NewJerseyZ]

A quickie here ... I've removed my A/C system (completely) in order to adapt some of my mods, but now there's an annoying red light that's continuously on located on the top left of my center console, near the temperature setting slide lever. No doubt it's detecting a low amount of refrigerant pressure. Is there a simple (non destructive) way to have this light be off --- for good?

1985 Turbo 5-speed GL

Thanks.

[Trbulnt]

As far as I am aware there is no low refrigerant pressure indicator on these cars. Solution is to remove the control console and remove the bulb.

[les_joey_paul]

probably just jump that switch

[Rick88ss]

Press the button and it should turn off.

[NewJerseyZ]

It's a button/switch? That's news to me ... but hey, I'll try it.
It is a very tiny light ... we are on the same page, right?

Here's a photo of what I'm speaking of ...

Gas Light.jpg

It's that little bright light to the left of the A/C switch/button.
It stays on all the time now. Pushing the A/C button in or out does nothing at all.

PS: There's also a cassette tape stuck in the player ... any suggestions?
(That's why that arrow light is on.)

[Trbulnt]

Well I learned something new! It does indeed mean freon is low. Makes me wonder where it gets its reading from and if its just a pressure transducer that completes a circuit with pressure in the system. If thats the case than it should be as simple as jumping that sensor to either ground or 12v depending of if its a one or 2 wire setup. I believe with all the questions you've had lately that a Factory Service Manual would be real handy for you to have.

[NewJerseyZ]

I have one ... imagine the number of questions I'd have if I didn't!

[wbnethery3]

Based on the FSM schematic, it looks like a simple switch. You ought to be able to jump the wires to each other (assuming you can find them after the delete) to make it think it's got refrigerant. Of course, there are other things that may happen when you do that. Not sure what else that switch keeps from coming on... this is on page HA-30.
AC schmatic.jpg

Good luck...

[NewJerseyZ]

It looks as though a bit of luck did come my way ... thanks wbn.

My mods required me to increase my fuel pressure to 3 BAR, so I changed my FPR to a Nissan 3 BAR piece, but unlike the z31 unit, it had no sender for fuel temperature. I read somewhere that one can simply ignore it and just leave it unattached, the wire that plugs into the fuel temperature sender. The FSM (EF & EC - 50) shows that a working sender is a thermistor that when tested should have given resistances for noted fuel temperatures. Leaving it unconnected is basically like having infinite resistance, and higher resistances indicate colder fuel --- very cold. Colder fuel is denser than hotter, so to compensate the ECU is leaning the mixture, perhaps too much. So I wired up a fixed resistor of what I feel is for an average temperature range --- 750 ohms, for around 100F. Once I wired up the resistor and turned the engine over to start, I immediately noticed that the GAS warning bulb no longer came on. Pushing the A/C button on and off did not make it come on, nor did running the blower fan. Does the car run any better? ... maybe, but at least the ECU doesn't think the fuel is colder than -20F. That's right, 20 below.

Why this works I have no effin' idea ... but it did.

Totally unexpected.

[Rick88ss]

Weird that now its off. Sorry I got confused with which light you were talking about. My 88 doesn't have it but I see what you mean in the pic. If it comes on again you should jump the 2 wires that used to connect to the pressure switch that was on the a/c drier.

[NewJerseyZ]

I get it now ... you thought I meant the light on the A/C button switch itself. I guess they dropped it (GAS bulb) in later years.
Thanks for the location of that switch. Schematics are great tools, but many times they don't give enough information.

[wbnethery3]

Lingering doubts...

The FSM does also have a wiring diagram, I just didn't copy it since you said you have the FSM... I copied the schematic to show that the switch is a two-wire and can be jumpered. I don't buy that the gas light went off because you wired a resistor to the fuel temperature sensor circuit. On my car, that sensor grounds through the block on a single wire spade connector on the FPR, which grounds through the mounting screws to the intake manifold. My FSM for the '86 doesn't show the sensor on EF-EC-50, but on page EF-EC-71, so maybe there are some differences. Your resistance of 750 ohms would produce a fuel temperature reading of around 120 F according the '86 FSM.

My question is what did you wire a resistor to? You seem to know your eletrical fundamentals, so I doubt you missed this, but is it possible you wired a resistor to the two connectors for the A/C pressure switch? They're in the same general area of the car and might be confused with the spade connector for the fuel temp.

No matter...if you're happy, I'm happy... maybe that little bulb just burned out...

[NewJerseyZ]

I pretty much agree with everything you said, but I'm pretty sure I got the correct wire. Here's a photo of the cut wire (and single spade plug) that was removed and replaced with the 750 ohm resistor ... (I'm keeping this incase I should ever find a way to reconnect an OEM sensor back in line.)
FPR connector plug.jpg

Now look closely at the FPR from this front view; it was taken back when I was still using the OEM FPR. You can make out the sensor connector plug just above the spark plug wires. It's that same plug as in the previous photo. (I strongly doubt that wire could have reached anywhere near the A/C components.)
mgp Front Portrait.jpg

Here's the finished product. The resistor is grounded to the upper intake manifold along with another grounding lug. The one with the resistor is to your left --- rear facing and then snaking forward. The resistor itself is inside the heat shrink tubing being used as an insulator.
Fuel Temp Sensor Resistor.jpg

So it's on the correct wire (99% sure)... and it's grounded through the manifold as the original sensor was.

Now, the question is ... does the light come back on when the ground is lifted? YES

It does not make sense to me either!

[wbnethery3]

Check the wiring color combination for the FPR temperature sensor in your FSM wiring diagram. I don't have mine (at work right now) but I'll look as well. That behavior sounds like it's simulating a closed switch for the refrigerant pressure. Being that yours is a different model year, and turbo vs. my NA, only other difference I forgot to ask about is whether yours had the automatic A/C or manual. The faceplate on yours is silver, mine is black so I'm not sure if that's just model year difference or also the auto A/C. Not sure if all those things matter at all, but better to know.

The other obvious way to confirm what you have wired the resistor to is to find the pin on the ECU for fuel temperature and test continuity.

Again, not sure it's important unless you want to know... I'm a little OCD and I sure as heck do.

[wbnethery3]

Forgot to mention - that connector doesn't look anything like what would plug into the pressure switch on the A/C drier... it also doesn't look anything like what's on my FPR temperature sensor, but I think mine has been replaced with a simple female spade connector. I'm probably the one who did it, but my memory is a bit dodgy...