Robban_C

I have a 1990 C4 that has started showing "Check Gauges" most of the time.
It flickers, blinks or lights constantly.
The drivers manual says that it means a problem with one of the values on the gauges but the gauges all show normal values.
Any ideas?

In guess that "Check Gauges" gets its information internally in the instrument cluster and that means that the signals from the engine works as they should since the gauges show normal values.
So, is it a bad solder in the instrument?
It all started after an engine wash and an engine wash wouldn´t affect the intrument.

Or are there a double set of senders on the engine?
In that case it could be a sender that lights up the "Check Gauges" lamp while still sending normal values to the gauges.
Or a sender cable in the engine room that got damaged while washing the engine .

antfarmer2

I would remove and clean all sender connections most likely you sprayed some crap up in them or rusted from the water

Cliff Harris

I suggest cycling through all the digital readouts to see if something is wacky.

I think the check gauges light is controlled by the PCM, so it might be seeing something funny that the analog gauges are not seeing.

Robban_C

Cycling the digital readouts? Sorry, I don´t understand that. Maybe it´s to early in the sunday morning here in Sweden?

Anyway, I´ll start checking the senders just as antfarmer2 suggests.

antfarmer2

Push the gauge button many times and see what it shows.

Robban_C

Gauge button?
I´m quite sure there are no gauge button on my car. Where should that be?
Or are you thinking about the pre -90 Corvettes? They have different switches, panels and gauges.

I have disconnected the oil pressure sender (that´s the one behind the distributor). Still get the "Check Gauges" light.
I have also diconnected the sender directly under the throttle house/thermostat housing. I guessed it was the coolant temp sensor and I was right since the temp gauge dropped to cold but "Check Gauges" was still shining.
I haven´t tested the oil temp sender yet. That one is close to the oil filter?

Note how the Check Gauges doesn´t light with full power.

bill mcdonald

If the C5 took on the same type set up as the C4 has, you probably are on to something here. I had so much strange **** happen in that car with that damn light. It would know if the charging system was off... then it would be okay. or the fuel sending unit would go crazy. I could reset it on the fly and it would be fine.

I don't know if it was more then a dummy light, or triggered by other strange things happening.

OP!
there is another sensor on the passenger side head for the coolant temp. so yes, some things are doubled up, but not really. I believe this is the one that goes to the gauges. I think the other by the throttle body one goes to the Computer. I don't know if it is smart enough to know if one or the other is messed up. I think you would be looking at check engine light instead

Also you say you washed the engine. Usually after a wash, the alternator dies. How is yours?

If you go around unplugging all of the sensors, you might find they connectors are brittle and they may start breaking. Maybe they already did. Maybe you put water into the electronics.

Push all those buttons in that picture and see if everything is working.

I would probably disconnect the battery. It is more a study in witch craft then anything technical.

antfarmer2

No mine is a 94 and mine gauge button is where your range button is. When I push it I get the differant readings from the sensors yours should be the same I would think.

TA

I think that started in 92 with the LT1. My 91 doesn't have a gauge button either.

Robban_C

Thanks, I´ll check that tomorrow.


It´s ok, 14,0-14,2 volts at idle.


Those that I have worked with wasn´t brittle at all but I agree, 25 years in a hot engine room kills plastics.


Already done that. No result regarding "Check Gauges".


I´ll try that tomorrow.

Robban_C

I only got some numbers of the range. I`ll try that again but if it is like TA says it wont help.
A function that cycles "Check Gauges" would really help as this might pinpoint which value is the one that initiates "Check Gauges".

I´ll read the electric scheme, hopefully to find if "Check Gauges" uses the same signals from the senders as the gauges do or if it has it´s own senders.

The oil pressue must have its own signal since "Check Gauges" most certainly only "listen" if oil pressure is ok or not (on-off) but the gauge uses an analog value.
But it would be the same with the temperatures as well? "Check Gauges" only lights up above a temperature threshold?

Robban_C

May I ask another question reagrding the same car? It will be off topic to the subject of this thread.
If I´m supposed to start a new thread in this subject, just tell me and I´ll do that.


The AC has stopped working. No, it didn´t happen at the same time as the "Check Gauges" problem.
All fuses are ok.
Zero volt at the AC pump clutch and if I connect the contact to clutch to the battery the AC pump starts spinning and one of the tubes on the pump gets cold and the other gets warm.
Is there a sensor somewhere that stops the pump if there isn´t enough AC fluid in the system? And does it close or open the electricity at low level?
Is there a relay to power the pump clutch and in that case, where is it?

Cliff Harris

You should start another thread because it gets too confusing with answers to both threads mixed together.

The low pressure switch does that. It is located on the top pipe that comes out of the evaporator housing.

Some cars have a relay and others don't. The earlier cars had the compressor control in the blower control module. There was a change to an external relay around 1988 (I'm not sure exactly when). Look next to the blower motor housing.

Cliff Harris

The coolant temperature sensor is different for the PCM (it is mounted on the water pump in LT1s). I don't think the other parameters have separate sensors.

Robban_C

I´ll do that but I´ll just report what I have done to the AC here and then we´ll continue the discussion in another thread.

There are totally three switches/senders on the evaporator pipes, one in the upper pipe just as you said and two on the lower pipe. The upper one looks like one of the lower ones while the other one is different.
I guess that it is two temperature senders and a low pressure switch.
All three senders/switches has two cables connected to them.
I removed the connectors one by one with no result and I connected the cables in the connectors with each other, one by one, but no result.
I took a brief look around the blower for a relay but didn´t find one.
That´s all about the AC for now, I´ll start another thread on that subject as soon as I can afford some time on it.

Robban_C

I just did that for 15 minutes and suddenly the AC started to work again!

And now it has been running for almost 15 minutes and the AC still works and no "Check Gauges" (yet)!
I don´t believe in witch craft but I might change my mind on this subject.
Is it common that disconnecting the battery solves such problems??

I would rather have found a real problem (such as a faulty sender) and fixed that. Then I would know that the problem was solved. Now I only know that the problem doesn´t show, for now.

I´ll get back with a report after driving the car in to the city and back later today.

Robban_C

Ok, so I drove it to town for an errand, 15 minutes there and 15 minutes back and had no "Check Guages" and I had the AC running as it should.

Still confused about the "witch craft" but it runs and that´s the most important for the moment.
Thanks everyone for your help!

bill mcdonald

Black magic every time!


When you get corvettes wet, they become possessed.

feel like washing the engine again?

Robban_C

Not until at least year 2020.