Operating temp & coolant level clarification

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Sep 2, 2013 | 11:46 AM

SeeFourSix

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From: Claxton GA

Operating temp & coolant level clarification

I see a lot of posts saying that "my car runs at 2xx degrees or 19x or 18x..." so my question is, are these numbers that were just converted from the Celsius reading or do some cars have Fahrenheit readings instead of Celsius like my 91 L98??

Reason I ask is I'm uneasy about the operating temp of my 91 because the analog gauge stays a little over halfway between the 100 & 260 mark (closer to the 260 side) but I've read where the gauge isn't linear so half way isn't 165.. My HVAC (Celsius reading) stays around 86-89 and has gotten to 90-93. When I see 91+ on the HVAC controls, the analog gauge is a hair closer to the 260 side than 'normal' and makes me very uneasy.. I have a feeling if my HVAC ever said 109 (228F) then my analog gauge would be pegged! I'm used to temp gauges showing less than "12 o'clock". This one is more like 12:30 or 1 o'clock if that makes sense... I have a feeling this is considered normal for the C4 but how can I be sure that what I'm seeing is accurate? I'm not used to cars running this "hot". I have a 180* thermostat, new hoses, fresh coolant, freshly cleaned radiator, and newer WP.

Also, should the coolant level of the surge tank by the passenger side windshield be at the very top (touching bottom of cap) all the time?

Sep 2, 2013 | 09:24 PM

SeeFourSix

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From: Claxton GA

anyone?

Sep 2, 2013 | 09:57 PM

vetteoz

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Quote:

Originally Posted by SeeFourSix

When I see 91+ on the HVAC controls, the analog gauge is a hair closer to the 260 side than 'normal' and makes me very uneasy..

I would only go by the ECM (HVAC ) temp reading

Sep 2, 2013 | 11:04 PM

OldCorvetteFan

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From: Athens, GA

We're quoting degrees F because that's the scale that the temperatures are displayed in. Why are you using the Celsius scale? Does your ENG/MET button not toggle the scales for you?

What do you mean when you mention readouts on the HVAC controls? Doesn't the HVAC control panel (on the center stack) only display either the AC setpoint or the outside temperature? If it's reading in degrees C, and you're seeing temps of 90C, then Claxton GA is a LOT hotter than I remember it!

Is this the display you're referring to when you talk about the HVAC?

You should be able to get the temp in degrees F or C on the center LCD display:

For your other question - yes, the coolant in the tank by the passenger side windshield is always full.

Steven

Last edited by OldCorvetteFan; Sep 2, 2013 at 11:11 PM.

Sep 2, 2013 | 11:12 PM

vetteoz

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Quote:

Originally Posted by OldCorvetteFan

We're quoting degrees F because that's the scale that the temperatures are displayed in. Why are you using the Celsius scale?

Because that is what is displayed by the HVAC head unit he is using to access the true temp seen by the ECM from the CTS

Sep 3, 2013 | 01:15 AM

tpfarm

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From: Palm Desert California

I also have a 91 that I have owned for 17 years and the temp gauge goes to about 245 or 250 before the fans come on . The gauges are just not accurate . Probably reading about 15 degrees to high. I think the 90 and 91 cars were the worst for this. I finally installed toggle switches in the forward cup holder and wired them to the fan relays so I can manually turn the fans on and off at will. I live in the Southern California desert and temps of 110+ are the norm in the summer.
BTW I used to live in Woodstock Ga. for most of my life.

Sep 3, 2013 | 06:44 AM

OldCorvetteFan

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From: Athens, GA

Quote:

Originally Posted by vetteoz

Because that is what is displayed by the HVAC head unit he is using to access the true temp seen by the ECM from the CTS

OK - I didn't know that you could use the HVAC head unit to read ECM data. How do you do it?

Does this mean that there are THREE data sources for coolant temperature? One for the analog gauge, one for the digital display, and yet another for the HVAC unit?

Or is this something that's exclusive to the early hybrid dash cars (1991 & 1992)? Wasn't 1993 when the LCD display was revised (along with the analog gauges)? I know that the LCD from the early hybrid dash is different from the one in my '95 (early LCD shown below).

Wait - I may have answered part of my own question. One of my other pictures of the early hybrid dash shows that it doesn't have a Gauge button.

So I guess I should reword my question - can you display the coolant temp on the HVAC panel with the newer hybrid dash, and is it from a third source or from the same source that displays temperature on the LCD?

When did the LCD display change from the 1991 style?

Steven

Sep 3, 2013 | 07:33 AM

SeeFourSix

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From: Claxton GA

Thanks for the info guys. This is proving to be a helpful thread for me. I'm using the HVAC controls by holding the up & down arrows until "00" displays then toggling to 16 and hitting the fan button. It will display the ECM temp reading but only in Celsius. If my instrument cluster will display the coolant temp digitally then that's new to me. How do I do that? Also, my black surge tank by windshield doesn't stay 100% full. Maybe its not drawing coolant back up from the expansion tank when it cools down. I'll dig into it.