Radco10

I just started driving my 91 after sitting for over a year (or two). I've noticed that the "Check Gauges" light starts flickering when I'm stopped in traffic for a minute then it will stay on until I get going again. This only happens when hot and I notice the charge needle gradually goes down. I don't know if this is normal or not. I never noticed it happening before. I have seen some TSB's that talk to the charging indicator fading when hot at idle but no mention of the "Check Gauges" light. Is the light supposed to come on like that when the charge indicator drops off? Is there a trip point for the "Check Gauges" light. If so, is it something to be concerned with? Any input would be appreciated.

Hooked on Vettes

With engine running, Check Gauges light comes on if oil temp. or coolant temp. are to high or oil pressure is to low. Look at which gage is in the cross hatch area.

Radco10

No gauges are in the cross hash area. Oil temp always runs low, all others are well within the band. I've only noticed the charging gauge dropping off, but still within the safe zone. The light goes out as soon as I am off idle.

RollaMo-LT4

The "Check Gauges" light will come on if you have high or low battery voltage.

You said your charge needle gradually goes down. Well, looks like it goes down low enough to cause the check gauges light to flicker. And no, it's not normal. When it gets that low (and the check gauges light is on), your charging system is not putting out enough voltage to maintain your battery. It's a warning, and you need to get it checked out.

How old is the battery? Replace it, if it's bad and have your alternator tested.

Radco10

Actually, it is a new battery. I do have a spare that I might try to see if the problem persists. Thanks for the input.

Hooked on Vettes

Check Gauges light is controlled by the CCM if there is High Coolant temp. or High Oil temp. or Low Oil pressure.

Have you verified the oil level?
Have you verified the coolant level?

Since the Check Gauges light flickers instead of being on solid it could indicate a bad connection some where at the CCM connector, the dash cluster connector or the CCM is flakey.

Out of spec. Low or High battery voltage should light the battery symbol on the DIC.

Some people have mentioned they get the SYS displaying on the dash cluster when the battery voltage is low but it causes no other problems.

RollaMo-LT4

From my owners manual:



Of course, it could be low oil pressure since it only happens at idle. But low output from the alternator at idle could also cause it.

Hooked on Vettes

Is that a 91's owners manual?

What does that manual say triggers the battery indicator in the DIC?

RollaMo-LT4

No, it's a 1996 manual

Of course low voltage is supposed to trigger the battery indicator light also.

Hey, I just threw an idea out there based on what he said about the voltage gauge dropping off.

I'll stay out of it now.

Hooked on Vettes

No need to stay out of it. LOL

I'm looking at a 90 owners manual.

I noticed in a 93 owners manual they say low fuel and high or low voltage can also trigger the Check Gauges light.

I also noticed in the 95 and 96 owners manual they said the transmission temp., low or high voltage and low fuel can trigger the Check Gauges light.

So it appears someone with a 91 owners manual needs to chime in and see what it says.



What strange is his Check Gauges light flickers, and the light is not On or Off.

Radco10

Sorry for checking back so late. I was out in the garage trying to isolate an oil leak, but that's another story.

The Check Gauges Light starts out flickering and then if I'm idling long enough it will come on steady and stay on until I take off again. And it only happens when the engine has been hot for a while. The temp gauge is in the middle. Like I said, the only one that seems to be abnormal is the charge gauge. Get this, when I drove home tonight, headlights on, it didn't occur. This is funky. I checked the Batt indicator on the DIC and it works as advertised - key on-engine not running-light on; engine running-light off.

Also, I checked my 91 owners manual and there is no mention of what will trigger the Check Gauges light. It says: "This light will come on briefly when you are starting the engine. If the light comes on and stays on while you are driving, check your various gauges to see if they are in the warning zone."

aminnich

Here is a really silly idea, but what the heck. You can send me a check if I am right (highly unlikely). Based upon the car having sat for a year or two and the voltage fluctuation when hot I would check the condition and tension of your serpentine belt. Like I said, just a thought and easy to check.

Radco10

Last Friday I changed the Oil Pressure Switch due to internal leaking. It was leaking up through the connector and oil was leaking down along the filter. While I had it off, I decided to change the OP sensor also. Not an easy job, I might add. Anyway, I drove it today and no more flickering "Check Gauges" light! I suspect that the leaking oil through the connector was causing a short. Thanks for the input.

Vette73

Found this thread with the new (?) search. Having the same problem with my '90 all of a sudden. The car is driven very intermittently so thankfully problems are few and far between. My son took the Vette out for a drive and was concerned that the temp gauge was way to the right. I explained how L98’s run hot and not to worry unless the gauge goes into the cross-hatch. He came home soon after and said that the Check Gauges light was flickering at idle. Checked the coolant temp thru the C68 and it showed 113C (235F). Very warm, but not hot. Oil pressure and temp seemed normal for a hot engine. Now, I know that the CCM gets it oil and coolant temp info from different sensors than the gauges do. My initial guess is that the oil pressure switch is weak (although it may be the coolant sensor for the CCM). Question: does anyone know how to test the oil pressure and coolant temp sensors? I don’t want to just start replacing parts which don’t need to be replaced.

wro87

On our 87' the gauges were acting up the tac was all over the place when at idle. Found that the battery (13months old) was bad and after the new one in all the troubles went away. Good luck wro87

schrade

See if you can find Mr agent 86 posts with FSM schematic for the spec voltage range on these 2 sensors.

Test is simple. Gettin' to HOT sensors with a multimeter isn't.