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I drive my 240 (SuperPolar B200F 1992) from 1996 as my daily driver, well cared for, and everything (now +650k km on the ODO).
I bought her when she was 4 years old with 110k km on the ODO.
Now I suspect (after 27 years, so no complaint) that the temp comp. board has failed since it's stable over 10 o'clock, so I got ready to do the infamous bypass. Of course, I have done all the needed maintenance in the cooling sector.
The temperature measured at the thermostat cover is around 88°C (the thermostat is 92°C) so there is no need to worry, but I can't stand to see the hand well over the middle.
But once I opened the instrument box I found no compensation board at all, and no bypass was done. I can exclude that something could have been done by the first owner (a failure in the first 4 years, no way!).
So, what is this mystery?
Until 3-4 months ago the hand was sitting in the middle with minor movements up.
My curiosity is how the meter can correctly work without the board and without the bypass.
Your help in solving this case is very much appreciated! Thanks!
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The Temp Compensation board was only equipped to USA Spec 1986 and newer 240s.
Judging from your post, you likely have a 240 that was sold for a different market.
Your car never would have had one from the factory for this reason.
--
http://dylans544.blogspot.com
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I guess you're right... my fault is to following brickboard.com only, and no European discussion boards :-)))
But I was misled, too, by the fact that in the past, the indicator was so permanently stuck just in the middle that I assumed I had a compensation board!!! :-)
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If you're running with a 92 deg thermostat then in my experience it's normal for the temp needle to run a bit above normal. Volvo specs two thermostats for B230s, Type 1 @87 deg and Type 2 @92 deg (ref 1994 240 Pocket Data Book). I've seen various arguments as to which one is most approprite to use under various operating environments and as well between turbo and non-turbo engines. People variously run with thermostats anywhere in between, even up to 94 deg, depending on personal preferences and thermostat availability. In my experience, and this may depend on market, the 87 deg thermostat is what normally came with the car from the factory. The temp guage would have been calibrated to that temp, so a 92 deg thermostat would read a bit higher. In my experience the difference with a 92 deg thermsoatat is reading more like 9:30 o'clock, so over 10:00 isn't what I would call normal, something's going on. In my experience with clusters without the temp comp board, they don't get that badly out of whack, in fact I find they remain quite consistent and stay in whack over the life of the car. An IR thermometer reading on the thermostat housing will of course be lower. How much, I'm not sure. Those temps stamped on the thermostats are opening temps. Full open is listed as 10 deg higher in the data book. Restricted coolant flow could drive the temp a little higher, especially if the ambient temp is summer extreme highs. When was the last time your cooling system had a good flush? new thermostat? new rad?
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now
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Mine is a B200F (n.a.) LH 2.4 and the original equipment was 92°, and, as you say, the hand of the gauge has always sat just a bit over the middle.
The problem came out some months ago, with normal outside temperature (75°F). During this summer, when we hit 105-107°F, and with AC working all the time, the hand didn't get any higher than over 10.
As for the cooling department, I made a complete refit 4 years ago (Nissen radiator, Hepu water pump, new visco-fan, new pipes, new reservoir, new metal pipe from the pump to the back of the block, and Glysantin Basf G64 antifreeze. Then, while trying to solve the issue 1 month ago, I got a new thermostat, fresh antifreeze, and a new reservoir cap (black 75kpa).
So I am almost sure (and I hope) it is an electrical problem (sensor, wiring, or stabilizer)
Unless it is something happening in the head (as I said the car has >650k km...). In that case... mmmh... I have to ask my wallet for a favor :-)
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The Volvo thermostat specs for the B200F are the same. This problem came on relatively recently and may be worse after the anti-freeze change? If so then you may have an air lock on the block side of the cooling system. Happened to me once after a water pump change and the temp needle went high, but I soon realized what was going on. When you installed the new thermostat, did you make sure it was installed right way around with the spring side down into the block and coolant? Did you make sure it was turned with the little jiggle valve weep hole at the top?
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now
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No, the issue came up before. The new antifreeze was part of the attempt to solve it. The thermostat install is correct (spring inside, bleed hole at the top)
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I'm gonna take a stab here and guess the
Temp Faker - Or That Temp Comp Board didn't become part of non-North American market cars.
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Art Benstein near Baltimore
The average dog is a nicer person than the average person.
-Andy Rooney
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Hi Art, your site has been my bible for years!!! And here is the right occasion to thank you for your great work!!!
I totally ignored EU 240 don't sport a compensation board.. but I suspect that >92 cars sold in Italy with the name Polar and PolarSuper have a lot in common with USA Limited Edition, so maybe ODO and Tach box (in KM of course). My mechanic who was the head of maintenance in an old Volvo dealer, suggested some failure in the compensation board, and I am sure he never have seen an American one! :-)))
But let's assume you are right (and I think you are...) the only check I can do to solve this misalignment between what the hand says and the measured temperature is the sensor and its wiring. Am I right?
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There are three components in your list of suspects, and yes, the sensor is probably the more likely of the three to cause an inaccurate reading.
Here's what I would do. Check the instrument voltage stabilizer first. It is so easy to do. All you need is a multimeter on voltage range. Pull the yellow wire from the sensor terminal at the cylinder head, turn the key on and measure 10 volts on the free end of the yellow wire with respect to the negative post of the battery. Run the engine briefly and ensure it stays right at 10 volts, not 11.5, not 13. If it sticks at 10V you've eliminated one not-so-likely cause.
Assuming it isn't the stabilizer at fault, I'd swap in a new sensor. They're not expensive and you don't have to drain all the coolant to put one in -- just be quick with the replacement.
The third item is, of course, the gauge itself. Not so easy to source and replace unless you're lucky to have a spare panel.
Then, there's always the possibility some flow problem exists in the head affecting the sensor's ability to be in the mainstream of the cooling. Well, that's one of the things a high reading is supposed to warn about, but I haven't seen it happen yet among my small fleet.
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Art Benstein near Baltimore
The reason a dog has so many friends is that he wags his tail instead of his tongue.
-Anonymous
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I have done today the first test: multimeter on sensor wire.
Engine off (the car was unused from yesterday): reads 9.88v
Engine on for around 3 minutes: reads from 10v up to 10.37v as a final value
Engine off after the test: shows 10.03v
Should I consider the test passed or failed? Can it be just the multimeter drift/accuracy?
Then I measured the resistance of the sensor and it was 378 ohms (real engine temp was around 40C°/105F degrees)
I guess I have to explore further, but in any case, at the next intake manifold cleaning, I will replace the sensor that is the original one (but 31yrs and 650k Km deserve a replacement...)
BTW: I found a temp gauge replacement (Volvo Genuine) currently sold at Skandix at 90.00€ ... a little bit expensive...
https://www.skandix.de/en/spare-parts/electrics/instruments/gauge-coolant-temperature/1038312/
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