biturbomax

it's not true.
the fans if the a/c is switched on do not operate at fully voltage (12v) but the fans are controlled by the frigen pressure sender when the a/c is switched on the voltage is 8,5v from about 3,5 bar of pression until 15 bar.
From 15 bar until 19 bar the voltage increase until 12v at 19 bar.
The flap are open at 30% from 3,5 bar until 15 bar and after open at 100%.
If your fan operate at fully speed immediately when you switch on the a/c your frigen pressure sender is defective and the security systen if the a/c is on set the fans at 12v.

Jim bailey - 928 International

Ken I really dislike the use of "Bla blah, blah" if you feel the need to edit please just use " ........ " The guy needs to understand how his car was designed to work and all that boring verbage is paraphrased from the workshop manuals. And just exactly how does your comment help him with his problem ? Now he is probably looking for a fan clutch . And by the way a "quattroporte " typically means a four door car. Quattrovalvola is probably what you wanted to say. see how a smiley makes everything O K !

biturbomax

in fact I had understood that Ken had a Maserati Quattroporte
No quattrovalvola but quattrovalvole
like lamborghini countach 5000 quattrovalvole.

Mrmerlin

I think Ken has the Quattroporte, its a big 4 door Maserati.
Not sure if its the Quattrovalvole version.
From the use of the IR gun it seems that his coolant system is operating correctly just the gauge is reading a bit hi. If the output water from the top hose is close to the thermostate temps than the hard parts are functioning the way they were designed.

I wonder if he may have had some water wetter in the coolant system this might have lowered the temp readings since it lets the water more fully touch the interior parts of the coolant system

Bituromaxx try cleaning the elex connections at the sender on the engine and make sure they are both insulated you can put on a piece of heat shrink on these wires.
The temp gauge should have a light that comes on when the bulb test is being conducted, clean the sender contacts first.
You may also want to look at the hot post connection and clean the big wires there and the 14 pin connector with a pink ereaser, disconnect the battery first/ (Hot post connection is under the hood and on the right side of the engine compartment sitting in the drivers seat)

biturbomax

I've noticed that when i turn my key on start but not when the engine is not running i don't have any red light in the position that i have signed on the photo.
Can be a signal that the temperature gage sender is defective.
Nobody can give the resistence value at the large pin of the temperature sender at about 18-20C° 65 F°.

PorKen

He could 'upgrade' to a clutch fan, if he really wanted.

My mistake, '86 quattrovalvole is what I wanted to say!

The light is probably burnt out. Those are special bulbs from '85, 928 641 983 00.



You can test the light by connecting the smaller connector at the gauge temp sensor to ground (earth).

Bill Ball

Seems that you have got a good handle on that part of the system. My basic point was just to indicate that the fans should come on with the AC switched on as a quick test of whether they are operating at all. If they don't then there is a problem that could have multiple causes but that might explain your high temperature complaint. The fans seem to be about the only thing you have not replaced other than the gauge and its sender.

I think I can sense your frustration, maybe with me for the incomplete information as well as with your temperature issue. Sorry I have not been of any help to you.

biturbomax

thank you Bill for help me.
Tomorow i will retire the new temp sender and i will instal it.
I have read this post on greg nichols site.

Instrument Pod


Temperature Gauge Troubleshooting

If you look in front of the oil refill port on top of the engine, there is a temperature sensor used by the vehicle's brain. Behind that is a round sensor with two spade lugs. The large one to the front is the temperature send signal which goes directly to the temperature gauge. The smaller one to the rear is the "engine has reached critical temperature point" sender, i.e.. it illuminates the overheat indicator at the top of the temperature gauge range.

You need to know whether your gauge is okay. The easiest way to check this is to briefly short the temperature send signal lug to earth and see if the needle goes to the far end of the hot range of your gauge. If it does, the gauge is good and the sensor needs changing. If so, check the resistance of the sensor relative to earth. It should be (from memory) about 140 ohms cold to around 50 ohms hot give or take.

To check the wiring, you need to check the continuity between the temperature send signal lug, and the respective point it enters on the LH brain cabling entry on rear of instrument cluster. Whilst there, again, short the temperature send signal (except at the instrument cluster end), briefly to ground and see if the needle goes to the hot end of the gauge. If so, a wiring problem, if not, the gauge needs repairing or replacing. I have repaired the gauges before although it is very fiddly work. Quite often, one of the fine inductor wires severs close to the solder post end and it can be fixed with a careful steady hand.

Regards,
Jarod


Nobody can confirm me this information?

Jim bailey - 928 International

The sending unit you want to look at is the one with a blue with yellow and blue with green wires the one on the driverside of the thermostat housing that screws straight down from the top vertical. It does not have a fuel injection style connector. The blue with yellow wire talks to the gauge. The blue with green goes directly to the central warning brain. The sending unit is grounded to the engine. Neither is connected to the LH or EZK brains. The temp sensor to the brains is NOT this one but is the one on the passenger side with the fuel injeection style connector but has nothing to do with the gauge or warning. The water temp sensor has a variable resistance element and an off on switch.

ew928

biturbomax, have you done a pressure check of the coolant system and the coolant cap?
I've been traveling so may not have caught up to everything.

And no one has done any work on your instrument pod so plugs to the instrument panel have not been disturbed. (disturbed as in cleaning the electrical contacts)

Mrmerlin

check the connection of the fuel injection style connector at the front of the radiator on the left side bottom. it could have come off and be affecting the fans operation

biturbomax

today i have replaced mi temperature gage sensor but nothing is changed.
i have also tested the temperatute switch on the bottom of the radiator and i have measure strange values.
I have measured with a thermocouple the water in the expansion tank and it was at 75 C° and the resistence was about at 5800 ohm the workshop manual say that the corret value must be about 3862 + - 150 ohm at 60 C° (i have meauserd the resistenze on the plug of the fan control unit and also directly on the fan switch)
I think there is a possibility that my fan goes on too much late because the resistence values are not correct.
The system work but don't work in the correct way.
What do you think about my idea? There's a possibility that the fan switch is defectice in this way?

NOTE:

I had not controlled the fan switch before because approximately 600 km ago I had already controlled it for a temperature problem.
One fan was blocked because my mechanic had mounted a A/C tube in wrong way.

Mrmerlin

its not uncommon for the lower rad switch to fail or lets say get lazy , try replacing it,

biturbomax

Hi people
I have solved my temperature problem.
The temperature gauge is out of calibration about 8 months ago the temperature gauge has decided that with the engine at normal temperatures would indicate the third white marks
When I bought my 928 about 4 years ago the temperature gauge had always indicated half way between the two white lines but now indicate the upper white line.
After changing 2 thermostats 1 radiator 1 fan switch 1 gauge temperature sensor on the thermostat body 1 expansion tank cap 1 expansion tank checked the operation of the flap and fan ECU controlled all temperatures of the engine with an infrared gun i have discovered that my temperature gauge is slightly mad slightly defective.
I discovered this with a fairly simple method i have attached my old gauge temperature sensor with the wiring of the gauge temperature sensor mounted on my engine plus a good ground on the engine i immersed the sensor in hot water i checked the temperature of the water with a thermometer and when the water was at about 90 C° (194 F°) my temperature gauge indicate the third white mark.
I think this is a common fault in many 928

Mrmerlin

your first clue was that the IR gun was telling you the internal temps of the top hose, if thats close to the temp of the thermostat then your system should be working properly.
Glad you figured out that you had a defective gauge.
Did you readjust your gauge or replace it??