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Hey all! Been lurking for awhile, bought my '94 Aventurine/Grey coupe about a year and a half ago. In that time I've put over 10k miles on it! One thing that has always bugged me a little bit is the temp gauge when its colder outside. I was hoping you all would be able to tell me I am either insane, or have something to change out.
Excuse the crude markup, but I wanted a visual aid. When I am driving in temps below 50-60s the temp gauge sits somewhere between the two blue hash marks (below the line I've marked as 1). If its colder its lower, warmer closer to line 1. It doesn't ever go into the "white box" at the bottom of the gauge once it warms out of that. Now when it is 60+ outside then the temp gauge rides right around line 1 usually until I'm at a stop and then it'll rise. If it gets to line 2 the fan kicks on and cools it pretty quickly. I've driven it hard above 90 degrees and it never once went above line 2.
I have no idea what thermostat is in the car, I haven't replaced it. I am thinking I might need to change that out since I fear its being over cooled when the temps are lower outside. It's really only a problem in the early spring and late fall here in Ohio, but it still bugs me.
I’ll edit this later with additional info, but me and a buddy both own multiple 968s and I’ve worked on many. I can tell you this - it’s hard to find 2 where the gauge readings mirror each other exactly. I fully believe that to be the inaccuracy of the gauges / issues with power supply and grounds and not the actual operating temperature of the engine although if the thermostat and fan switch are both 30 years old, some fresh ones (of premium quality) won’t hurt.
It is common for the fans to switch on at one temperature and off at a lower, but yours are switching on at a temperature higher than any of mine do. Also, none of mine stay in the blue range when I’m driving in cooler temperatures so your engine thermostat may be opening too early or stuck open. I hope this helps and again, disparities do exist in the operation of these gauges - I’ll edit with some additional info later. Time to go “make the donuts”…
Picture of the normal location of my temp on my 1993 968. At this level, my Durametric software tells me I'm operating at approx 200F so I now only look at this in case it gets a lot higher.
Separately (sort of), it's 75F here today, and when I turn on the A/C compressor - the engine fan comes on almost immediately.
(damn I need to do something about the scratches on the plastic)
Picture of the normal location of my temp on my 1993 968. At this level, my Durametric software tells me I'm operating at approx 200F so I now only look at this in case it gets a lot higher.
Separately (sort of), it's 75F here today, and when I turn on the A/C compressor - the engine fan comes on almost immediately.
(damn I need to do something about the scratches on the plastic)
I don't see that as an accurate representation of 200 Fahrenheit. Again, these gauges read all over the board.
I don't see that as an accurate representation of 200 Fahrenheit. Again, these gauges read all over the board.
Cliff
Huh... speaking of that is there a particular temp that each line is supposed to represent? Though it obviously doesn't seem like an exact science haha. I'm thinking because the gauge behaves normally for me (between lines 1 and 2) when its warmer out, but reads lower when its colder that is probably more likely a thermostat issue. If it read the same(ish) regardless of outside temperature that'd more likely be a wiring/gauge issue.
I had an opportunity to drive one of my cars this weekend. Once the thermostat "cycled" a couple of times, the gauge hovered right over the first white mark and stayed there until the car stopped. When stopped, the radiator fans activated long before 1/2 gauge. The OP stated that his fans activate at the 2/3 mark which makes me question if his low speed fan circuit is functioning. It sounds like his fans aren't operating until the threshold for high speed operation is reached and the 2/3 mark may even be a late activation for that.
I found the following on the Pelican Parts forums here (from 2006! haha), I'll drive the car over the next day or so and pay better attention to when the fans kick on to see exactly where it happens. I'll also check the resistors then as well. I think its worthwhile to note the car has never overheated for me and never has gone above Line 2 (in my image, 100 in the below image).
Follow the diagram above to check the slow and fast speed operation of the cooling fans.
It looks like your slow speed is not working. Check fan resistors. Fan resistors located in the engine compartment below the windshield under the black plastic cover passenger side. Fans run in slow speed when coolant temp reaches 92C or slightly higher. Fans run in high speed when coolant temp reaches 102C or slightly higher. See, 102C is close to red. That's the reason why it's close to overheating. During summer, it might be late for fans to run in high speed and car will overheat.
I found the following on the Pelican Parts forums here (from 2006! haha), I'll drive the car over the next day or so and pay better attention to when the fans kick on to see exactly where it happens. I'll also check the resistors then as well. I think its worthwhile to note the car has never overheated for me and never has gone above Line 2 (in my image, 100 in the below image).
This might be dumb but I'll ask it, that's °C right?
Hey all, reviving this a bit to post the solution! Always get frustrated when I find threads with my problem and no solution in sight.
The issue here was an old thermostat that was not operating in spec anymore. The car had an 83C thermostat but it was opening at 76C and it was fully open at 85C. It's now been replaced with a new 83C thermostat that was tested before installation and the temp gauge is now behaving as I would expect not going below the 80C mark on the diagram in the thread above.
Separately (sort of), it's 75F here today, and when I turn on the A/C compressor - the engine fan comes on almost immediately.
Just to contribute another very late fact into this thread. When the AC compressor is running, the engine fan will also be running, period. You can test this by having ignition ON but engine OFF and press the button to get AC and the fan will kick on (even with engine off and cold). Totally normal behavior for these cars.
04-27-2023, 10:31 PM
Temp Gauge Question
