MainePorsche

Guys,

This indicator went on while driving today, and now goes on at my startups. MY COOLANT TANK SENSOR IS FAULTED AND I'VE HAD IT DISCONNECTED FOR 3 YEARS. The sensors two wires (Blue/Red & Brown) are well capped and separate. I've went through the WD and it is a simple circuit switch to central warning brain.

I do plan on dealing with the reserve tank change out, but not now. My engine coolant system is not factory anymore (DC Control now) and works great. I am very attuned to my system and watch it carefully, but this RED light is most annoying.

Your thoughts on something I am overlooking would be appreciated.
Thanks in Advance,

Craig

dr bob

Look at the coolant pressure switch, mounted in one of the vent lines just forward of the coolant reservoir. It's wired in the same loop as the level switch, and is probably causing the light. It's there to "qualify" the low level alarm.

MainePorsche

Thanks Bob.
Will do tomorrow.
Just wondering why the pressure switch would fault independently when the ACTUAL fluid level was normal upon inspection and the system is functioning fine.

FredR

+1 on what Dr Bob says.

The coolant switch appear to be two halves bonded together- on mine the thing literally split in two. This puzzled me a bit as to why coolant was not all over the place but in the end I concluded that under normal circumstances the system does not reach atmospheric pressure boiling point.

In your case it would seem that the pressure switch has gone to the alarm condition for whatever reason. If you pull the plug off the switch and the alarm dissappears that should verify the issue [I think].

There was a general consensus that there is no real reason for having this feature and most who have this issue by-pass it with a small tube of the same size/length as I did for a work around.

MainePorsche

Fred, thanks for the info.
My system runs very cool and I'm just puzzled as to why the switch failed and alarmed. Like the coolant level tank sensor, it is a simple circuit switch so is very simple to bypass. Will get into it when the sun is up here.

MainePorsche

Fred, just curious when you're switch split (and failed ? ) did you get the central warning ?

FredR

It's a bit like me- getting old and knackerred I suppose!

I assume that under "no pressure" the diaphragm inside the switch has no contact. As to what caused your switch to detect an alarm condition remains to be seen.

I am not even sure if my tank coolant level alarm is working [or not] but then I regularly scan the temperature indicator on the dash to ensure that appears to be working normally as that and the oil pressure gauge are the engine status indicators I value most.

Rgds

Frd

FredR

No central alarm that I remember. I would be interested to know what you find when you take a look. Hopefully this explains the alarm but it is possible it could be something else

I was working on the cooling system pre-emptively changing hoses and decided that I wanted to remove the expansion tank and clean it out. In the process of disconnecting the small lines to the tank the pressure switch literally fell apart in front of my eyes. It looked as though the bonnet was bonded to the body but....?

No idea what they cost to replace but all these stock item little gizmos seem to have a $100 minimum purchase price whereas something "generically fit for purpose" can probably be found for bottom dollar if only one knows where to look. My approach is to refurb or omit if possible but for anything absolutely essential I stump up.

Rgds

Fred

MainePorsche

I was hoping to use the pressure sensor switch as my 'early warning' sensor as I disconnected the level sensor. I've had an experience on my first 928 (an 86.5) when the short hose ruptured. The 'early warning' coolant warning came on BEFORE the temp went up. I wasn't as knowledgeable at the time and did NOT immediately take measures to keep the temp from going up. The result was misfiring and coolant on one of my spark plugs.

The reservoir change out is on the horizon, but I understand it is a bear of a job and I don't have the time right now. I'll examine the pressure sensor with a mind to change it out (looks like a quick and easy) and keep that as the 'early warning' sensor until I can change out the reservoir with it's level sensor which I deem the more reliable of the two for the 'early warning' function.

FredR

I cannot visualise how the pressure sensor could provide an early warning but then I do not fully understand how this sub system is supposed to work.

My original thinking was that the system pressurises as an indication of system healthy but practical experience suggests the system does not get hot enough to initiate boiling and thus no pressure being generated. I seem to remember Bill Ball experienced this when he was puzzled as to why his system was not capable of holding pressure and yet he had no issues with boiling.

The expansion tank is a bit tricky to remove and replace but it is quite do-able- just expect to lose skin on a knuckle or two!

I omitted the pressure switch out of immediate necessity following a credible list recommendation - have not experienced any issues since but that does not mean all is well. I would feel a bit more comfortable if I fully understood how this system works.

MainePorsche

Fred,
Thanks for all your comments.
I'll have a look at matters shortly and will most likely perform a tube change out to bypass if physically damaged. I am very conscious of the issue of overheating with our aluminum heads. With my DC Control system I am able to set the temp at 180 deg for the fluid, and it has remained as such even after the warning went off. I just need to have piece of mind regarding the physical state of this inline sensor.
Kindly,
Craig

FredR

Craig,

What exactly is a DC control system? Is there a modulating control valve rather than the self regulating thermostat?

Feel free to respond when you have had some kip!

Rgds

Fred

MainePorsche

Fred, after my amplifier failed I researched in order to find a more 'modern' replacement. I used the FK-95 unit. This unit is our controller and amplifier in one waterproof unit. It is configured to measure radiator temp via an included sensor we install, AC fan activation at 30% and can be increased by 10% if desired. I also used other input pins to have all of our sensors (torque converter temp, intake temp, high pressure AC sensor) to activate fans at 30% if tripped. I had a lengthy thread called something like 'Alternative Fan Control...' Alan helped me configure the secondary temp sensors to tie into the system. I did this under the front seat where the controller lived. The secondary sensors are all grounded switches and I configured them into a SPST relay so as to activate the respective pin on the new controller. The unit has a built adjustment so one could set engine temp at what you want. I kept the 180 deg factory setting. System works like a charm with adjustable fan speeds. The only oddity it has is when I turn off a hot engine, the fans run a bit to cool it down and right before turn off it makes a high frequency 'electrical sound'. I like it as it sounds 'modernish'. Ducman uses this unit too, and like it. I placed the unit where the amplifier was. Aside from inserting the sensor into the radiator, it was mostly careful wiring work. The company is in Silicon Valley and Brian Baskin, proprietor, was very knowledgeable and helpful.

http://www.dccontrol.com/constant_te...ontrollers.htm

FredR

[QUOTE=MainePorsche;14141186]Fred, after my amplifier failed I researched in order to find a more 'modern' replacement. I used the FK-95 unit. This unit is our controller and amplifier in one waterproof unit.

Craig,

Interesting- I will try to read up on this. I presume the bit that failed was the kit that controls the fans. I am a bit suspicious of these things in that when I tried to do some check [a good while ago] it seemed to me that they do not send full bus voltage to the fans- more like 10 to 11 volts if my memory serves me correctly thus why I was looking into different ways of running the fans on full voltage- at least during the hot season.

MainePorsche

In regards to the new DC unit I replaced the original system with there was a failure when it had gotten wet. I called Baskin. He sent me a new one saying that the first one was not sealed correctly. He said he personally oversaw the construction of the second unit.

In my running the car my fans never go to max. They did go to max when they first got wet and they were running like an aircraft. I know they were at 100% for I was on the phone with Baskin performing diagnostic tests at the various points and pins on the unit.