Engine Temp Gauge
 

Hi all,

I'm just wondering, can the dealer or a specialized Volvo shop reprogram the dash computer (by removing the hysteresis from the engine temp gauge) so that the engine temp gauge needle would actually fluctuate and show real engine temp values? You see, what I don't like is that once the engine warms up, the temp gauge is pretty much useless because as long as the temp stays within roughly 160-210 deg F the temp gauge readings never change!

In older cars the temp gauge needle would move up and down (or left to right) as appropriate for engine running conditions. If you have noticed, the gauges these days no longer have proper scales with temperatures written on them and that's because the temp gauges no longer provide the information they were once designed for - engine temp!

I guess this is a problem in all recent cars. I'm not sure why they have made the temp gauges pretty much useless these days.

If anyone can provide an authoritative response to this I would appreciate it.
Thanks.

Piterrr

It's not a problem. As long as the temp is with those temp ranges, the car will operate properly.

If you want a true reading, get an OBD-II tool that shows other values and exact measurement.

www.ScanGauge.com

www.Ultra-Gauge.com

Doubt anyone at the dealer would know what you're talking about (using all those engr words..!) so in word, no, even if they understood what you were saying, they don't have the means to "re-program" the cluster; you're talking about re-engineering the firmware in the flash or prom of the cluster control module. Unless you're a really good hacker, or had the source code, or etc., not gonna happen.

At the end of the day, do what rspi suggested; that will get you the closest, but even that will have some substantial latency; but probably good enough for what you want I would think.

Yeah...I do realize this is somewhat of a technical shop talk, but I would expect a competent tech to know what I'm talking about. After all, what are all these dealers charging sky high labor rates for if not hi levels of knowledge? I do have an OBD scanner that will easily show the true engine temp readings but driving around with this tool hooked up at all times is, diplomatically speaking, inconvenient. As an embedded systems engineer, I have some idea how these systems are designed. The software that runs on the cluster microprocessor likely includes code along the lines of this conceptual pseudo code:

1. take current sensor reading
2. convert it to digital form
3. if the reading falls within the range 160...212 deg (sample range, different on different cars) do not change the position of the temp gauge needle, ELSE increase or decrease the position of needle slightly (as appropriate) but only when the reading is outside of this range
4. repeat steps 1-4 above

What I hope is doable is that the range in step 3 should be programmed to be much smaller and thus affect the position of the gage needle much more frequently.

I'll ask the local Volvo shop on Sat, just curious what they will say.

Piterrr

Huh??? Is likely what you will hear. I drive with mine installed all the time, I have no issues with it.

Cool; an embedded engr huh; we should talk...

Back to your question; yeah but remember, step 3 in your list (latency and/or hysteresis) could be inherent in the hardware (sensor and measurement circuit) and/or designed into the cluster firmware. How do you intend to modify either w/o knowing the original design? Unless you got a source at volvo (in which case we really need to talk!) you're talking about reverse engineering your car and then modifying it to do what you want; what i was inferring in my first post.

gdog,

There are certain software parameters that every car manufacturer makes certain the dealers have easy access to for the purpose of reprogramming. I just hope that the temp gauge hysteresis is one of them. Example? - Consider speedometer calibration. Typically, on many cars you have different options for tire sizes (the diameter matters here). If you fit bigger tires without speedometer calibration you would be showing too low a speed, and too high with smaller tires. So they install whatever size you want and then download the correct conversion parameter to the cluster computer so that your speed shows the proper value regardless of tire size.

You suggested that the latency and hysteresis could be done in hardware. It is certainly possible but I can guarantee you this is not how they do it. That's because it is FAR cheaper and more flexible to do this in software. Consider what would happen if a manufacturer designed the hardware for the temp gauge with hysteresis, say, 160-210 deg. If the following model year they release a car with more efficient engine that runs cooler, the new engine's "comfortable" temp range might be 150-200 and I can assure you they are not going to redesign their electronics to handle the cooler engine. All they do is they update the software that controls the cluster computer.

This is the whole point of embedding microcontrollers into every imaginable electronic device, from toasters to rockets. You design hardware once and then modify software if you want to change functionality (within limits) and far cheaper at that, due to reduced number of electronic components.

Piterrr

Good luck with that. Stop by the dealer and let us know how things work out.

Just for clarification, i didn't suggest the latency of the hardware was designed in, just that it may be the nature of sensor and hardware circuit response. Which is taken into account in the firmware design too of course...

Let us know how many confused looks you get from the guys at the dealer; but then maybe you'll get lucky; let us know...:)

Actually this is a big problem. When the fan fails the engine can easily boil over as just one example,.. all the while the temp gage stays put right in the middle. Many engines have been ruined by this insane design. Apparently there are a lot of novice posters here that are unaware of this issue. Many have upgraded their DIM units to post the actual temp. But once again this is a serious issue and just another design flaw that has cost loyal Volvo owners much.