Fluctuations in temperature guage readings - Page 2 - Alfa Romeo Bulletin Board & Forums
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post #16 of 49 (permalink) Old 08-05-2015, 03:55 PM
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When I make a hard right turn, the temperature can spike up to 220. On a hard left turn, the temperature dips slightly below the normal reading.
I've seen this a number of times on various L4 Alfas. The root cause was the connection at the temp sending unit. Some were repaired by squeezing the female spade for a tighter connection while others required a light re-staking of the rivet that holds the male spade to the sender (I've seen some male spades so loose they could be spun in a circle!).
Also ensure that the sparkplug wires are well clear of the sender.
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post #17 of 49 (permalink) Old 08-06-2015, 12:01 AM
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On my S3, the temperature guage normally reads between 175 and 185 depending on the season. When I make a hard right turn, the temperature can spike up to 220. On a hard left turn, the temperature dips slightly below the normal reading.

Are these fluctuations normal? I'm imagining either a bad temperature sensors or an air pocket in the cooling system that allows the coolant to slosh around.
As long as your coolant levels are OK I really cant see a problem - its an Alfa and Alfa's have their foibles - on the S2 it is difficult to airlock the system - don't know about the S3

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post #18 of 49 (permalink) Old 08-06-2015, 08:09 AM
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I've seen this a number of times on various L4 Alfas. The root cause was the connection at the temp sending unit. Some were repaired by squeezing the female spade for a tighter connection while others required a light re-staking of the rivet that holds the male spade to the sender (I've seen some male spades so loose they could be spun in a circle!).
Also ensure that the sparkplug wires are well clear of the sender.
this is the most sensible suggestion yet... but it begs a question... since the sensor is a resistance to ground device where zero resistance ( grounded ) is full scale and " open circuit " is "zero temp" then if he is seeing 220 sometimes and lower temps at others and it is a loose sensor wire then the higher temps would seem to be accurate as the connection thru the sensor to ground is occasionally good vs the lower temps which would indicate a loose or worse connection to ground... so... if you are right ( and probably are ) doesn't this imply that the guys car is actually running pretty hot ?
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post #19 of 49 (permalink) Old 08-06-2015, 08:17 AM
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so... if you are right ( and probably are ) doesn't this imply that the guys car is actually running pretty hot ?
Agreed.

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post #20 of 49 (permalink) Old 08-06-2015, 11:05 AM
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My Spider's temp gauge does this slightly even on gentle swerves. Sure looks and acts like inertia induced to me.

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post #21 of 49 (permalink) Old 08-06-2015, 06:26 PM
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My Spider's temp gauge does this slightly even on gentle swerves. Sure looks and acts like inertia induced to me.
then why don't all the instruments do it like synchronized swimmers ? they all share the same movement type except the mechanical tachs...
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post #22 of 49 (permalink) Old 08-06-2015, 10:23 PM
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Temp gauge on my S3 does the same thing.

Al
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post #23 of 49 (permalink) Old 08-07-2015, 03:40 AM
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Temp gauge on my S3 does the same thing.

so let me understand this... everybody's instruments here wave their needles around in the corners like a Madonna video and mine is the only alfa whose instruments actually behave like real instruments ? wow... what a lucky guy I was when I bought this car...
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post #24 of 49 (permalink) Old 08-07-2015, 07:57 AM Thread Starter
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I checked the spade connector to the temperature sending unit. The male spade is secure to the unit and the female spade is clean and tight. I didn't see any problem with the wire connected to the female spade. Just for fun, I checked the gauge when the wire is disconnected (needle to far left) and when the wire is connected to ground (needle to far right). I also checked that the wire has enough slack to handle shifts in the engine position during turning and I rerouted the wire to go below the fuel injectory wires. No change in symptoms.

I will next change the radiator cap and try to bleed the system as stevesxm suggests.

Earlier stevesxm asked when I first noticed this behavior. It was after I changed the head gasket in June 2014. Prior to that, I think I recall slight motion in the temperature gauge on hard turns, but not to the magnitude I described in my initial post.
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post #25 of 49 (permalink) Old 08-07-2015, 09:57 AM
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I'm not buying the inertia theory. On a right turn the needle will move to the left. If inertia were the root cause then on a hard right turn the temp would read cooler not hotter.

Jason
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post #26 of 49 (permalink) Old 08-18-2015, 08:41 AM Thread Starter
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Thanks ljayr for pointing out that inertia can't be the root cause since the needle moves in the same direction that I am turning (needle moves right when turning right).

I thought I would provide an update on a few more things that I have tried.

With the engine running, I tried wiggling the wire to the temperature sending unit to determine if there is an electrical problem. I wriggled every portion from the blade connector to the bundle that goes behind the firewall; no change in the temperature reading.

I next tried bleeding the coolant system again with a new radiator cap. I jacked up the left front portion of the car to ensure the coolant bleed screw near the thermostat was at the highest point. I opened the heater valve, cracked the bleed screw, and ran the car for 15 minutes with a steady coolant drip. I then removed the radiator cap, topped off the coolant, and reinstalled the cap. No change in symptoms.

At this point I am stumped. I don't think the engine is running hot since the reading is 175-185 when driving straight, which seems about right.

Kim - 1987 Spider Quadrifoglio (~170K original owner miles)
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post #27 of 49 (permalink) Old 08-18-2015, 09:12 AM
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Originally Posted by bongju View Post
Thanks ljayr for pointing out that inertia can't be the root cause since the needle moves in the same direction that I am turning (needle moves right when turning right).
You can't really assume that, no, as the needle is counterbalanced around a pivot.

Anyway, if you're really worried you could get an IR thermometer and measure some temperatures. But given everything you've done at this point it sure sounds like you're chasing an instrumentation issue and not an actual problem.

Tom

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post #28 of 49 (permalink) Old 08-18-2015, 02:13 PM
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Could be a magnet/electromagnet issue. The gauge has a coil and a permanent magnet inside it. If a wire carrying a good amount of DC current (ammeter wiring?) was moving around it might cause this.
Just a WAG on my part............
Bob

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post #29 of 49 (permalink) Old 08-19-2015, 02:51 AM
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well... if its not kreeger waves from planet zircon, then what is it ? remember engineering rule number one... think horses... not zebras.

what do we know for fact ?

1) simple electrical automotive instruments have been built the same way for a 100 years from the cheapest brit ones to the most expensive veglia in Ferraris and such.

2) they are all built the same way. they are ALL just voltmeters with wheatstone bridge circuitry ( if I remember correctly )where the dial face is changed to indicate whatever value they are measuring....

3) they all work the same... a measurement is taken of resistance between a reference signal and ground. less resistance gives you longer scale... more resistance gives you less scale.

4) no gage I have ever seen in all conditions has ever demonstrated movement due to g force nor would I expect it as the physics don't support that conclusion in any way. we are not talking gas gages here which have mechanical floats that are affected etc.

5) since all the gages are effectively the same, then every gage in the car would have to be affected the same by whatever the cause is... and they are not. so that implies that it is not a systemic problem...

so... what does that leave you ? a sensor that needs a good ground and a reliable system voltage. variation in either will give a calibration error or cause the needle to shift position... we know it isn't system voltage because all the gages would do it.

so... what if the engine ground were weak and the threads on the sensor corroded such that when the car turns one way, the engine ground is weakened and the other way returns to normal... ?

how do you test this? strip a wire and hose clamp it to the hex on the sensor and run it to a perfect ground NOT on the engine and secure it.

measure the resitance from neg bat to that wire to confirm its good... now try it.

after that all there is is changing sending units and gages. all this is predicated on the notion that there are no real temp swings occurring that are actually being accurately indicated.
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post #30 of 49 (permalink) Old 08-19-2015, 03:42 AM
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My temperature gauge must be from planet zircon because it swings slightly when swerving the car, even just a little. It's enough to notice if you're looking at it.

John Stewart
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91 164S
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