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Old 01-08-2019, 11:08 PM   #1
darkmountain
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Default Temp faker board bypass question.

Good day,

In a pinch due to work and lack of free time before a long drive I took my 240 to my usual mechanic who I trust for some work before about 900 mile round trip drive. the service included spark plugs, oil change, diff oil change, and he bypassed the temp faker board due to my temp gauge always reading cold or not registering.

The day after the repairs was when I had to make my 8 hr round trip. The wagon drove great and the temp stayed right in the middle the whole trip. Made it home and got in my car to drive to work the next day. As I drove the temp reached to about halfway between the red zone and normal temp.. about 10 o clock. The previous day it did the same but dropped after a few miles of driving. Now my temp needle stays around the 10 o clock mark the whole time I'm driving as if its running hot. Has any of y'all had this experience after your faker board was bypassed? I just don't like thinking the engine is constantly running hot even at highway speeds.

Just wanted to check or get some advice if it could be something else causing the engine to run hot. I have the plastic shroud under my engine and coolant/oil looks nice and clean. Its a 93 245 with no engine mods. I unfortunately don't know what brand plugs were installed, though I trust my mechanic as both him and his brother drive 240's.

Thanks guys!
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Old 01-09-2019, 12:24 AM   #2
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Originally Posted by darkmountain View Post
Good day,

In a pinch due to work and lack of free time before a long drive I took my 240 to my usual mechanic who I trust for some work before about 900 mile round trip drive. the service included spark plugs, oil change, diff oil change, and he bypassed the temp faker board due to my temp gauge always reading cold or not registering.

The day after the repairs was when I had to make my 8 hr round trip. The wagon drove great and the temp stayed right in the middle the whole trip. Made it home and got in my car to drive to work the next day. As I drove the temp reached to about halfway between the red zone and normal temp.. about 10 o clock. The previous day it did the same but dropped after a few miles of driving. Now my temp needle stays around the 10 o clock mark the whole time I'm driving as if its running hot. Has any of y'all had this experience after your faker board was bypassed? I just don't like thinking the engine is constantly running hot even at highway speeds.

Just wanted to check or get some advice if it could be something else causing the engine to run hot. I have the plastic shroud under my engine and coolant/oil looks nice and clean. Its a 93 245 with no engine mods. I unfortunately don't know what brand plugs were installed, though I trust my mechanic as both him and his brother drive 240's.

Thanks guys!
Had a similar problem after cutting yellow wire and plugging for more direct read and it was thermostat.
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Old 01-09-2019, 12:36 AM   #3
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Had a similar problem after cutting yellow wire and plugging for more direct read and it was thermostat.
That was my next thought. The thermostat is less than a year old but who could know. Im still learning to be honest. Just trying my best to pin point where to start.
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Old 01-09-2019, 12:41 AM   #4
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I had one from autozone barely last me for 2-3 years. Then got few degrees lower from NAPA and drilled super small hole all the way on top of that on and been riding it for few years without problems.
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Old 01-09-2019, 01:21 AM   #5
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I had one from autozone barely last me for 2-3 years. Then got few degrees lower from NAPA and drilled super small hole all the way on top of that on and been riding it for few years without problems.
I guess my main question is the fact that it read normal one day and the next day runs hot? I know with these old cars its a matter of an issue surfacing within the time it takes to fill up your gas tank. I feel like the standard with this 240 and my third now, is that when one thing is fixed another issue presents itself It is funny because this is the nicest 240 Ive owned cosmetically. Im not the most mechanically inclined but I am tentative to my cars and just want to keep it running well and efficiently.
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Old 01-09-2019, 01:33 AM   #6
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I guess my main question is the fact that it read normal one day and the next day runs hot? I know with these old cars its a matter of an issue surfacing within the time it takes to fill up your gas tank. I feel like the standard with this 240 and my third now, is that when one thing is fixed another issue presents itself It is funny because this is the nicest 240 Ive owned cosmetically. Im not the most mechanically inclined but I am tentative to my cars and just want to keep it running well and efficiently.
Normal here, fixed high-idle about a month or 2 ago, then few weeks ago went into fixing >1k rpm stalls, now trying to battle pouring atf and rattling reverse trans.
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Old 01-09-2019, 02:31 AM   #7
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This is normal behaviour when the faker is bypassed, 10oclock is not overheating
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Old 01-09-2019, 08:05 PM   #8
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It could be the thermostat is worn. Without the temp faker. As the enine warms up you should see a peak and then the temp settle down. If the peak takes a long time after warmup to settle down then it could be a slow reacting/worn out thermostat.

You don't say what temp thermostat you are using. It might be that you are using a hot 92C one and it ran cooler because of all the highway driving. Now you are local and it's hotter because of the thermostat. I like to use the 87 or 82C versions.

More wiring issues in my 93 245 than any other 240 I've had. lol. I like it a lot anyway.
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Old 01-09-2019, 10:42 PM   #9
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Wahler or Vernet thermostat. 87 C.
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Old 01-09-2019, 11:17 PM   #10
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It could be the thermostat is worn. Without the temp faker. As the enine warms up you should see a peak and then the temp settle down. If the peak takes a long time after warmup to settle down then it could be a slow reacting/worn out thermostat.

You don't say what temp thermostat you are using. It might be that you are using a hot 92C one and it ran cooler because of all the highway driving. Now you are local and it's hotter because of the thermostat. I like to use the 87 or 82C versions.

More wiring issues in my 93 245 than any other 240 I've had. lol. I like it a lot anyway.
This is good advice. Iíve noticed the peak and drop on mine as well.

OP, you need to get the car to operating temp (when the needle is higher than expected), and then measure around with an infrared thermometer. Temps should be 180F-200F.
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Old 01-10-2019, 08:17 AM   #11
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Originally Posted by apachechef View Post
This is normal behaviour when the faker is bypassed, 10oclock is not overheating
This. 10:00 is still within the normal range. I don't think you need to worry.
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Old 01-10-2019, 09:56 AM   #12
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This. 10:00 is still within the normal range. I don't think you need to worry.
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Old 01-10-2019, 10:25 AM   #13
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Quote:
Originally Posted by apachechef View Post
This is normal behaviour when the faker is bypassed, 10oclock is not overheating
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Originally Posted by 57plymouth View Post
This. 10:00 is still within the normal range. I don't think you need to worry.
not all 240 gauges will have the same readout when the board is bypassed. In fact, the past 3 I have bypassed all read differently, even though coolant temps were a consistent 180F on all 3 vehicles. I had one that reads about 1/3 way up, one slightly over half, and one that reads 3/4 the way up.

The only way to be sure is to VERIFY coolant temps with another gauge, like an infrared thermometer.


My 93 245 had the faker and it worked great, then i bypassed it and the gauge would read 3/4 or so and I constantly thought it was overheating. I made a thread like 2 to 3 pages long, changed out every cooling system component etc just to find out that the gauge just reads there normally even at 180F. Needless to say, I verify temps on every car I own now. No more guessing. I’ll check with 2 or 3 different IR thermometers so I get the best possible guess.

I got so tired of staring at a 3/4 gauge that I added an inline potentiometer and tweaked the gauge to read where I want when it’s at operating temp. Been perfect for 2+ years now. And it still reads linearly so no worries about not catching an overheat situation if there were to be one.
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Old 01-10-2019, 03:19 PM   #14
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I just bypassed one, still needs a 100ohm resistor test to get it exactly to 9 o'clock. However i can't really understand what goes on here.
Brownie has no temp faker board as its an early cluster, but its rock solid at 9 o'clock. By rock solid i mean i never saw it moving anywhere when its warmed up. Beige 1980 donor car just got a cleaned and "calibrated" early cluster (i couldnt see the temp needle when i got the cluster lol) via a 100 ohm resistor. This too works wonderfully in that car.
Newer 240s have the exact same cooling system...
I still did not test a newer faked gauge, but i do think they are calibrated a little bit different because the faker board. I will check and chime in later...

I just dont get it what was wrong with the early setup, which works just perfectly...
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Old 01-10-2019, 03:41 PM   #15
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The temperature fluctuation during driving conditions and during warmup scared all the little old ladies so Volvo added the faker board to calm the stressed nerves over a gauge moving while driving.
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Old 01-10-2019, 03:49 PM   #16
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Originally Posted by petiww View Post
I just bypassed one, still needs a 100ohm resistor test to get it exactly to 9 o'clock. However i can't really understand what goes on here.
Brownie has no temp faker board as its an early cluster, but its rock solid at 9 o'clock. By rock solid i mean i never saw it moving anywhere when its warmed up. Beige 1980 donor car just got a cleaned and "calibrated" early cluster (i couldnt see the temp needle when i got the cluster lol) via a 100 ohm resistor. This too works wonderfully in that car.
Newer 240s have the exact same cooling system...
I still did not test a newer faked gauge, but i do think they are calibrated a little bit different because the faker board. I will check and chime in later...

I just dont get it what was wrong with the early setup, which works just perfectly...
Weird stuff. I have 2 93 240s and when my wagons gauge consistently read high after the bypass, I did so much (useless) testing and parts swapping/cannon to figure out why. I swapped clusters entirely, I swapped gauges separately, I ohm tested the entire circuit from the sending unit to the cluster connector..Can't remember the results but they were probably inconclusive. I cannot remember if the high reading gauge followed the cluster to my other car and still read high, or if it read normally and the new cluster also read high in the 'overheating' wagon. Maybe I'll try again..

All I know is that it's a huge waste of one's time to worry about a high reading gauge after the board is bypassed. Simply get the vehicle to normal temps, wherever the gauge reads, and measure with an IR thermometer. Could read near the red zone, doesn't mean anything at all. I just figure get coolant temps to around 180F-190F, then use a potentiometer or resistor to center the gauge, OR alternatively, deal with a high reading gauge.

One could also just reinstall the faker board to keep themselves happy, but I recommend against this in case of an overheat situation that might not be caught by the gauge. Just my
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Old 01-10-2019, 03:56 PM   #17
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From what I recall the gauge itself is calibrated by bending the pointer so it aims at the calibration mark on the face of the gauge. if the car is running at a good temp. I don't see why you can't bend the pointer to where you feel more comfortable like at nine o'clock.
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Old 01-10-2019, 05:38 PM   #18
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It could be the thermostat is worn. Without the temp faker. As the enine warms up you should see a peak and then the temp settle down. If the peak takes a long time after warmup to settle down then it could be a slow reacting/worn out thermostat.

You don't say what temp thermostat you are using. It might be that you are using a hot 92C one and it ran cooler because of all the highway driving. Now you are local and it's hotter because of the thermostat. I like to use the 87 or 82C versions.

More wiring issues in my 93 245 than any other 240 I've had. lol. I like it a lot anyway.
I want to say it was an 87 that I last purchased. Itís been about a year, but who knows I could have bought a 92c. I did experience the peak and drop the first night I drove the car and the day after during my 8 hr trip. The next day after getting home was when I experienced the peak and it never really goes down after that. It did drop to half way zone today but peaked back up before I got to work. Iím thinking itís a worn out thermostat bc that would make the most sense to me with the gauge readings. Thank you for the input!
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Old 01-10-2019, 05:40 PM   #19
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Going to throw out another possibility here. My gauge after performing the bypass mod always showed just a tick above the 9 o'clock position. Recently I swapped heads and when I swapped the head I also swapped in a better crank pulley/harmonic balancer. When removing the old pulley I realized that it had delaminated from the rubber and had been spinning. After installing the better pulley (that didn't slip) my temp gauge consistently shows at about 7 o'clock.

Just something to consider but after that 900 mile trip your pulley may be slipping a bit. Worth a check.
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Old 01-10-2019, 05:42 PM   #20
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VW/Audi was known for installing oil temp senders that would cause the gauge to read lower than actual temp.
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Old 01-10-2019, 05:45 PM   #21
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Another thing to consider is the design of the water pump impeller.
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Old 01-10-2019, 06:19 PM   #22
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Quote:
Originally Posted by dl242gt View Post
From what I recall the gauge itself is calibrated by bending the pointer so it aims at the calibration mark on the face of the gauge. if the car is running at a good temp. I don't see why you can't bend the pointer to where you feel more comfortable like at nine o'clock.
I think the "bending" gets done from behind, and rather than matching a gauge to a sender, the "special tool" resistor should be the calibration standard (68 ohms) so that a crusty sender doesn't wind up the new reference. Make sure the stabilized gauge voltage sticks at 10.0 over all alternator loads.

In this image, you can see the rest position and the "gain" are separately adjustable through an access hole in the rear of the gauge by moving the toothed platform with a small screwdriver.



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Old 01-10-2019, 08:28 PM   #23
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Thanks for correcting my fuzzy memory Art!
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Old 01-11-2019, 12:58 PM   #24
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I've still got one of those "faker" boards, brand new, with no future in my stable...

Who wants it?
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