Reading the Analog Temp gauge

[Bruce Nunnally]

I don't recall who posted this originally, but here was one interpretation of the temperature readings at different lines on the Northstar V8 analog gauge:

Let me know if you made this gif and I will be happy to credit where due.

[JasonA]

That doesn't go for all years, if it's accurate for one particular year.

On my '97, the 12:00 mark is valid for all indicated temperatures of about 185-222. It will creep off the 12:00 mark towards the "12:30" mark (1st to the right of straight up) if the temperature creeps up into the middle 220s. From there, it'll quickly move over to the 1:00 mark (2nd to the right of straight up) if the temperature climbs to 230 or higher. I've only seen 230+ once, and it didn't really go past the 1:00 mark, indicated as 224 in the image above.

[Ranger]

That does not look right Bruce. Both my '02 & '03 as well as my daughters '99 run at 12:00. According to my '97 (digital), normal was 206 (summer) -213 (winter) which would lead one to believe that the guage should be at about 1:00 (or less) according to that gif from my observations.

[Bruce Nunnally]

Well, glad I posted then. Can someone with a northstar and a digital temp on the DIC display start resaving some values and we can make a new image file.

[JimD]

I can obtain some readings for my '98 and '04 with my interface box and laptop. Understand any pictures and data gathered will be very specific to the manufacturing tolerance of my coolant temperature sensor and the degree of damping applied to the gauge signal.

One limitation is that the highest temperature I am willing to sample is the point at which the cooling fans are commanded ON at low speed (approximately 223 degrees).

I will have to think long and hard about blocking air flow to allow the temperature to rise enough to command high speed fans.

[JimD]

Here is the readings I get from my '98 model using this interface box http://obddiagnostics.com/index.html and sampling only coolant temperature at more than 2 times per second. No airflow, parked in driveway, ambient air at 77 degrees.

The gauge needle sits rock steady at 12 o'clock for temps. from 190 to about 216 degrees. Remember the display is digitally driven and tends to be well damped to avoid alarming movements in this range.

The needle will be at one full needle width north of 12 o'clock when the fans come on at low speed at 223 degrees. You might not even notice one needle width if you were not paying (too much) attention. The needle moves down quickly to the 12 o'clock and the fans go off at 212 degrees.

The engine would sit there all day at idle cycling the fans on and off and you would never see the needle higher than one needle width above 12 o'clock.

I had to completely block airflow with cardboard plus torque brake the engine at 1,500 RPM to get the temp. above 223 degrees. At 230 degrees, the needle is one width below the first mark (past 12 o'clock); at 235 degrees, the needle is one width beyond the first mark. The temp. at the second mark is in the range of 248 to 250 degrees. Needle movement "appears" to be less-damped in this range.

The fans go from low speed to high speed at 234 degrees.

Sorry, but no pictures; I had all could do to make notes and pay attention to the temp. readings.

[JohnnyG]

As far as I can tell, without the benefit of the interface box, my '99 operates identically to the description that JimD has posted. I have never had the needle go more than one needle width past the 12:00 position, except for a short period in Florida while sitting in traffic on I95. 99% of the time the needle never strays from that middle mark...........I like it!

[WarrenJ]

I've followed this thread with some amusement. It seems that some of the most technically aware folk I know have reduced themselves, like a gaggle of housewives, to discussing:

12 o'clock.

1 o'clock.

A needle width before/after 12 o'clock or a particular hash mark.

And, "what year is that valid for?"

Here's a question: WHAT IS THE darn TEMPERATURE? Answer me that and I'm happy (hopefully). Cadillac dropped the ball on this one, likely because they didn't want to field questions about wide temperature swings. The long-term damping and lack of numeric indicators on the gauge is just simply wrong. If the gauge is to be useless, simply replace it with an "idiot" light as in previous years and let's simply be done with it..

How would you feel if your tachometer displayed average RPMs for the last 10 minutes?

Regards,

Warren

P.S. I didn't write "darn" and I sure didn't write the other word in lower case!

[JimD]

....

Cadillac dropped the ball on this one, likely because they didn't want to field questions about wide temperature swings. The long-term damping and lack of numeric indicators on the gauge is just simply wrong.

....

I still miss the days of an oil pressure guage and an ammeter; at least give me the display option with a soft toggle.

Cadillac and most of GM (with the possible exception of truck chassis vehicles) has a long term track record of mishandling the ball on certain features. That's part of how you go from making every other domestic sale to one in four.

[Bruce Nunnally]

Warren makes an interesting point, but in summary I would offer the following instructions on reading the analog temp gauge: if the needle is in the red, the engine is too hot, and you should be concerned. If it is still in the white, then that's still ok.

My CTS temp guage is always straight up, which I prefer. I did note that Time-sert has product for the 3.6L now.

[thu]

The 2000 Ford F-250 PowerStroke that I used to have had the exact same issue. The needle pointed to the 'normal' position for a range of coolant temps.

[WarrenJ]

if the needle is in the red, the engine is too hot, and you should be concerned. If it is still in the white, then that's still ok.

Isn't that the near perfect description of an "idiot" light? Go vs no-go?

I'm far more interested in that in-between area that allows me to anticipate potential problems and see them approaching . . . . THAT is the part of the meter scale that should be expanded.

Regards,

Warren

[JasonA]

Here's a question: WHAT IS THE darn TEMPERATURE? Answer me that and I'm happy (hopefully).

Warren, does your Eldo not allow you to display the temperature via the DIC? That's the only way I know my real temperature...

Isn't that the near perfect description of an "idiot" light? Go vs no-go?

That's what these gauges are. "Analog idiot lights". As Thu pointed out, that's how many Ford gauges operate as well. Engines are so reliable today that you don't really need to be keeping a constant monitor on temperature, oil pressure, etc anymore (although many of us still enjoy doing that). But your average Cadillac owner doesn't know or care. That's not exclusive to GM. I'd wager that not 2 out of 10 luxury automobiles give you a true un-buffered temperature reading...heck, not just luxury automobiles...anything anymore. Our Grand Caravan is the same way. The temperature gauge reads one position...unless the temperature REALLY climbs like sitting in traffic without the A/C on. The cooling fans on that engine come on slightly sooner than the Cadillac's fans (about 215 if I recall correctly), but it's the exact same setup.

[JasonA]

To add to the above, I took note this morning of what the marks "below" the midpoint map out as:

1st mark (bottom): after about 95*F, the temperature indicator will start to move off the 1st mark.

2nd mark: the indicator will reach the 2nd mark at about 105*F.

3rd mark: the indicator will reach the 3rd mark at about 135*F.

4th mark: the indicator will reach the 4th mark at about 165*F.

5th mark (straight up): the indicator will settle here when the coolant temperature reaches about 190*F. On my car, the indicator actually settles a touch RIGHT of straight-up, to make the needle APPEAR straight up from the driver seat. 190*F is right about where my car normally runs, so if the engine cools down a bit, like coasting down a hill in colder weather, the gauge will actually fall to the left a little bit as the temperature might sag into the 185*F neighborhood.

On the hotter side of the scale, my '97 operates generally as described by the posts above.

It's been so dadgum hot here lately that when I get in the car in the morning, the temperature gauge usually starts at or above the 2nd mark. Yes, the coolant never cools to below about 105-110*F. The inside of the garage stays sweltering in the evening, and is still "sandy beach warm" in the mornings, even if the temperature outside has dipped into the mid 70s.

[JasonA]

My interpretation of the gauge is included here.

[The Fred]

To add to the above, I took note this morning of what the marks "below" the midpoint map out as:

1st mark (bottom): after about 95*F, the temperature indicator will start to move off the 1st mark.

2nd mark: the indicator will reach the 2nd mark at about 105*F.

3rd mark: the indicator will reach the 3rd mark at about 135*F.

4th mark: the indicator will reach the 4th mark at about 165*F.

5th mark (straight up): the indicator will settle here when the coolant temperature reaches about 190*F. On my car, the indicator actually settles a touch RIGHT of straight-up, to make the needle APPEAR straight up from the driver seat. 190*F is right about where my car normally runs, so if the engine cools down a bit, like coasting down a hill in colder weather, the gauge will actually fall to the left a little bit as the temperature might sag into the 185*F neighborhood.

On the hotter side of the scale, my '97 operates generally as described by the posts above.

It's been so dadgum hot here lately that when I get in the car in the morning, the temperature gauge usually starts at or above the 2nd mark. Yes, the coolant never cools to below about 105-110*F. The inside of the garage stays sweltering in the evening, and is still "sandy beach warm" in the mornings, even if the temperature outside has dipped into the mid 70s.

Are your ceilings well insulated?

Do that and make sure you have airflow in the attic

[JimD]

....

The inside of the garage stays sweltering in the evening, and is still "sandy beach warm" in the mornings, even if the temperature outside has dipped into the mid 70s.

My garage is attached. When I put a hot car in the garage, I pop the hood open, turn on a box fan and leave the garage door open at least 12 inches for as long as possible.

This reduces the major heat load on the common wall between the house and the garage.

[JasonA]

The ceiling is probably not well-insulated. I did what Jim suggested today. Actually, I just left the whole garage door open for a while. It dramatically affected the temperature inside the garage, for the good.