I hadn't given it too much thought; it seems like it causes more problems than it fixes.

From what I gather, the temp compensator board takes the (linear?) input from the temp sensor, and flattens it near the center. When it works the needle spends most of it's life near the center of the gauge, making the owner feel happy that they own such a precision piece of machinery -regulating the heat to within 5 degrees or so.

If I'm right, then I'm rather pissed off. Don't get me wrong, I like the idea of having a steady temp needle, but I HATE the idea of instrumentation purposely giving your wrong data. Damn trick!

I would absolutely rather know what the engine is *really* doing. Does anyone have any experience with eliminating the compensating board alltogether.

Any thoughts?

Am I totally off base on what the board does to start with?

Grr..

As an aside...

Volvo may be guilty, but they aren't as bad as Ford...My pappy has a 1993 Ford F150 that has an oil gauge in the cockpit. I noticed that the needle is ALWAYS 2/3 of the way to "high". After a bit of research I find out that the gauge is indeed real, but the "sending unit" is just a switch with a resistor in series. If you've got enough oil pressure to close the switch, then the gauge reads 2/3. Junk, junk, junk! (the truck caught on fire this week, too)

That's all for my nightly rant.

-Steve

Steve,

Here's a proposed "fix" for deleting the Temperature Compensation Board as originally posted by Alan Furman on Monday, 15 January 2001, at 6:36 p.m. (I was going to try this on one of my cars, but haven't had a board go bad lately--knock on wood). All the standard disclaimers apply . . .


"After evaluating and tracing the entire circuits of the temperature gauge and the temperature compensation board, here is the solution for eliminating the board entirely from the system. This will make the gauge more accurate and allow it to fluctuate precisely with the engine temperature."

"Note also that this was done after doing the "don foster" fix (new op-amp and transistor), which was unsuccessful."

"Remove the display panel, and remove the cover (unscrew and unplug the voltage regulator, and remove the front window panel)"

"You should be able to see the infamous temperature compensation board on the lower right. Unplug it."

"For reference's sake, assume the following numbering for the pins. Looking down at the display (speedometer should be facing you and in the middle), the furthest pin to the left is ONE, then two, three, and four. (These are the pins that normally connect into the temp-comp board)."

"Solder a wire from pin 1 to pin 3 to bridge past the temperature compensation board."

"Now, for all of those who are wondering how this works. Power goes into both the gas gauge and the temp gauge from pin 4 (which comes from the voltage regulator). This power runs three places: both gauges and the temperature compensation board. Since both gauges are still powered from the printed wire that powers pin 4, disconnecting the board does not affect power into the gauges. Pin three runs to the wiring harness that runs directly to the temperature sender-- a temperature-varying resistor on the block. Pin 2 is an internal ground for the operational amplifier on the temperature compensation board. Since you now do not have a temperature compensation board in your dash, this pin is now irrelevant. Pin one receives current after it has passed through the gauge but before it has made it to the temp-sender. Therefore, by connecting pin1 to pin3, you safely eliminate the ever failing temperature compensation board from your system."

Hope this helps,

Steve A-
--
Steve Anderson (3 x 83 + 91 = 700k+ miles)

Does this Temp Compensator board exist in 1991 700 series as well??
--
Regards,

Here's the procedure to bypass the board, go to ... http://www.brickboard.com/RWD/index.htm?id=406894

Good luck
--
Bill Crump ('91 245SE & looking)

Actually...I think that what it does is "compensate" for minor variations in temperature to keep the gauge reading steady. My understanding is that the board can be disabled/bypassed, but your gauge will be very erratic and fluctuate with every minute change in engine temp.

I was having a look in my 86 245 cluster and found that the TCB was not there (the guide it sits in and the PCB pads were there), I think this is unusal for that year, perhaps the cluster was replaced by some PO. Anyway I do not see any weird fluctuations however it does get hotter as you stop in traffic after cruising for a while. Mine has been known to rise to 2/3 in summer in traffic but it always comes back down as you get moving.
Pretty much what you would expect the actual engine to do. Should I feel lucky.
Karl

I think you should feel lucky, yes. The boards are prone to failure, and whenever a gauge is reading high on the temp scale, the first thing is to "make sure the engine actually is running hot"

Good advice considering how erratic the gauge/compensator boards are, but not acceptable (in my book, anyway) for a gauge. So with your setup, if you are reading hot, your engine probably is running hot.


Maybe all the board does is even out minor fluctuations,but it sure seems to hae a strong bias towards the center of the gauge. I will be sitting at idle and the gauge will be PINNED to the center, then SUDDENLY, within a few seconds, it shoots up to 2/3 or so. It's more than just a simple low-pass filter, that's for sure.

I would rather see my needle start to creep up so I can react before it's at 3/4 or whatever.

I think it would be interesting (and just maybe it's interesting enough for me to do) to put a second gauge in the car, uncompensated. It would be interesting to compare the two readings as the car warms up.

-Steve