Pressure sensor
04-13-2002, 10:05 AM
#1
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Pressure sensor
Hi,
Can someone tell me, what is the purpose of the pressure sensor in the cooling system - That's added to the car from model 1984
Regards from Erik in Denmark
928 S(2)- 1980/84 - Euro - Aut. - Black/Black
Can someone tell me, what is the purpose of the pressure sensor in the cooling system - That's added to the car from model 1984
Regards from Erik in Denmark
928 S(2)- 1980/84 - Euro - Aut. - Black/Black
04-13-2002, 11:28 AM
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Thank you for your logic answer, but ... I tested today, the pressure valve in the cap is opening before the pressure sensor close.
Regards from Erik in Denmark
Regards from Erik in Denmark
04-13-2002, 04:48 PM
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Jay,
I do not think the pressure sensor is mentioned in the shop manual - see page 90-37
I added a cooling system pressure tester to the small hose on top of radiator.
Looking forwards to get you comments - Thank you
Regards from Erik in Denmark
I do not think the pressure sensor is mentioned in the shop manual - see page 90-37
I added a cooling system pressure tester to the small hose on top of radiator.
Looking forwards to get you comments - Thank you
Regards from Erik in Denmark
04-13-2002, 06:13 PM
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The coolant level sensor is connected to terminal Yellow 14 on the Central Warning System, and the sensor is open when the coolant level is OK, closed when the level is low.
The coolant pressure sensor is hooked to the same terminal, and is electrically in parallel to the level sensor. High pressure closes the sensor switch.
Given the way that the sensors operate, and the way that they are wired, the only conclusion that I can reach is:
The pressure sensor will set the coolant warning light if the pressure in the cooling system exceeds the preset limits.
I think that it is a bit odd that the Porsche engineers apparently felt it necessary to incorporate a warning in case the cooling system pressure cap fails to open, causing an over-pressure condition.
The coolant pressure sensor is hooked to the same terminal, and is electrically in parallel to the level sensor. High pressure closes the sensor switch.
Given the way that the sensors operate, and the way that they are wired, the only conclusion that I can reach is:
The pressure sensor will set the coolant warning light if the pressure in the cooling system exceeds the preset limits.
I think that it is a bit odd that the Porsche engineers apparently felt it necessary to incorporate a warning in case the cooling system pressure cap fails to open, causing an over-pressure condition.
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10-16-2003, 02:59 AM
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Hallo,
warming up this old thing, but my pressure switch just broke and I am interested in what it does on my car.
The pressure switch 928 641 513 00 was leaking. Written on the switch is 0,1 + 0,1 bar, 6-12 V. VDO-number 111/006/001.
In my 94 GTS the pressure is connected to ground on one side and to the instrument cluster, connector 3, pin 6 on the other side.
So first I was thinking that it would cause a warning when the switch closes, connecting ground to the pin 6 on the cluster, but simulating the switching function does not!! trigger any warning. Although the drivers manual lists all warnings, no "overpressure" warning is mentioned.
The pressure written on the switch 0,1 + 0,1 is different from the release pressure of the coolant reservoir cap 0,8 - 1,1
Looking forward to get you comments - Thank you
Regards from
Harald
warming up this old thing, but my pressure switch just broke and I am interested in what it does on my car.
The pressure switch 928 641 513 00 was leaking. Written on the switch is 0,1 + 0,1 bar, 6-12 V. VDO-number 111/006/001.
In my 94 GTS the pressure is connected to ground on one side and to the instrument cluster, connector 3, pin 6 on the other side.
So first I was thinking that it would cause a warning when the switch closes, connecting ground to the pin 6 on the cluster, but simulating the switching function does not!! trigger any warning. Although the drivers manual lists all warnings, no "overpressure" warning is mentioned.
The pressure written on the switch 0,1 + 0,1 is different from the release pressure of the coolant reservoir cap 0,8 - 1,1
Looking forward to get you comments - Thank you
Regards from
Harald
Last edited by Harald944; 10-16-2003 at 03:15 AM.
10-16-2003, 04:22 AM
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Hello Harald,
That's a good question - Porsche installed it from the S2 model, and it gives alarm if/when the pressure reach to a certain value and it is simply installed parallel to the flow sensor.
You can easily run without
One reason for installing this could be, that Porsche got a claim from a customer where the radiator or cooling hose cracked due too high pressure (The safety valve in the lid did not open) - If that happens with high speed on the German highway that will cost a new engine!
That's a good question - Porsche installed it from the S2 model, and it gives alarm if/when the pressure reach to a certain value and it is simply installed parallel to the flow sensor.
You can easily run without
One reason for installing this could be, that Porsche got a claim from a customer where the radiator or cooling hose cracked due too high pressure (The safety valve in the lid did not open) - If that happens with high speed on the German highway that will cost a new engine!
10-16-2003, 04:49 AM
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Good morning Eric,
thank you for your answer, but I think it must be different, as a pressure of 0,1 +0,1 bar is completely normal in the system. At 0,8 - 1,1 bar the overpressure cap comes into the play, if that would fail, I would understand a warning pressure switch that would close at lets say 1,3 bar.
But the switch is 0,2 bar only.
Second, if I would close the pressure switch manually, simulating a to high pressure, I need a warning light if you would be right. But there is no warning, regardless if the pressure switch is open ore closed....
So all this makes no sense for me.
Happy if I am wrong and you could get it clear.
Harald
thank you for your answer, but I think it must be different, as a pressure of 0,1 +0,1 bar is completely normal in the system. At 0,8 - 1,1 bar the overpressure cap comes into the play, if that would fail, I would understand a warning pressure switch that would close at lets say 1,3 bar.
But the switch is 0,2 bar only.
Second, if I would close the pressure switch manually, simulating a to high pressure, I need a warning light if you would be right. But there is no warning, regardless if the pressure switch is open ore closed....
So all this makes no sense for me.
Happy if I am wrong and you could get it clear.
Harald
10-16-2003, 06:25 AM
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Dear Harald,
I do not know from where you have the 0.2 Bar - Are we talking about two different pressure sensors?
I found my old sensor and I admit that very difficult to read, but I think it shall be read as follows:
o.1+O, 1 bar, 6-12 V
If you look in the el-diagram you will also admit - When either the flow or the pressure sensor goes on the ground signal goes to the controller unit for the warning lamp
I do not know from where you have the 0.2 Bar - Are we talking about two different pressure sensors?
I found my old sensor and I admit that very difficult to read, but I think it shall be read as follows:
o.1+O, 1 bar, 6-12 V
If you look in the el-diagram you will also admit - When either the flow or the pressure sensor goes on the ground signal goes to the controller unit for the warning lamp
10-16-2003, 10:56 AM
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Is this device a switch or a transducer? Having a low voltage printed on it as you see makes me think it may produce a variable signal (into the fan control module???).
10-16-2003, 11:24 AM
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My pressure sensor was leaking on my 87, I replaced with a new one and now I get the coolant light come on intermittantly and it is the pressure sensor that causes it. If I release the cap then the light goes out ...... the cap is relatively new, just put it down to an overactive sensor.
I heard mention somewhere it is used as an early warning system for head gasket failure.
Chris
I heard mention somewhere it is used as an early warning system for head gasket failure.
Chris
10-16-2003, 12:54 PM
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Chris,
It seams that you got a new 'tired' pressure sensor - Relatively easy to test, if you have access to cooling system pressure tester (A small hand pump with pressure indicator you place on the reservoir instead the lid)
I can't imagine how the pressure sensor can 'smell' a future gasket failure
It seams that you got a new 'tired' pressure sensor - Relatively easy to test, if you have access to cooling system pressure tester (A small hand pump with pressure indicator you place on the reservoir instead the lid)
I can't imagine how the pressure sensor can 'smell' a future gasket failure