Central Warning Light comes on when accelerating
 

Does anyone have a idea why my Central Warning light on MY82 928 comes on when accelerating? No other individual warning light comes on with the Central Light. I can turn the light off by pressing the reset button, but the next time I accelerate, the light comes back on:confused:http://forums.pelicanparts.com/uploa...1283889753.jpg

Check your coolant level. Maybe it sloshes backwards as you accelerate, moving away from the censor?

Auto or manual gearbox?

Beautiful car btw!

check your timing belt tension with a proper gauge, the extra forces of acceleration may tighten the pulling side of the belt just enough to slacken the tensioner side of the system causing the tensioner to send a "loose" signal to the central warning system.

Wouldn't the belt tension warning light come on as well then? But good call Anthony, that's probably it.

Do you have one of these:
http://members.rennlist.com/pirtle/tb17.jpg

Good suggestions guys. I'll check both the coolant level and the TB tension.
(I need to borrow the tool from tmpusfugit first SmileWavy ). Thanks.
Mike

But the light wasn't added until 1985 -- there is no timing belt tension detector.

That said, if it were an 85-up car, that would be a good thought.

Thanks 'riber.bentsen'. I went out and checked the water tank and found that it was pretty low. I had a hard start / no start condition since May of this year. While trying various things, I think I may have caused the coolant level to recede. A lot of backfiring and rough running. Since then we've got the car back running fine. :D
I just added coolant, but since we are having the affects of a tropical storm (lots of rain here in Conroe, TX), I have not taken the car out to test it. BTW it is an automatic.
I'll post results later.
Thanks again,
Mike

You can call me Nick.. (Or Niels, but you 'mericans don't seem to be too familiar with that name)

;)

And Landseer you have an incredible knowledge about these cars. I learn something in here every day!

Thanks Niels. I totally agree with you re: Landseer's knowledge. He was a great help in getting my shark running.
Mike

Fluid Slosh -
 

Hey mproseusa, Perhaps you have the very rare “High G-Force Sensor” option. ;)

As mentioned above, you are right to normally expect an accompanying dash warning light for the specific problem that triggered the master warning panel. Perhaps, you are getting a "liquid level slosh" from a marginal fluid level that turns on - then - off the dash light while the master warning panel's holding function makes sure it has your attention. This could be potentially any fluid on board - low fuel, oil level, radiator reservoir, etc…

One other thought - I have seen the brake pad thickness warning circuits trigger some very strange results as well. This is especially true when the wiring had been poorly spliced, jumpered or hanging loose.

Good Luck, Michael

Thanks Michael. Good points. I have been '928' educated beyond my imagination. I am also concerned with the wiring as I've been able to "pull" insulation off wiring without much trouble. I do believe though that the water level in the tank was low. I had noticed fluid on the floor of my garage after running the engine for quite a while. The fluid appeared to be clear, and I took a slight taste of it. It was sweet, which is a good indicator of antifreeze. So when Niels suggested low coolant level, I wasn't to surprised, just embarrassed.:o Once I get the TB/WP changed out, I have brake pads, wiring, etc. on the to do list.
Thanks again,
Mike

if you getting low coolant i would suggest to replace the heater control valve and the short hose as well as the coolant bottle bottle cap, this should cure most leaks. usually a light coming on during hard starts is a low fluid.
you might consider adding fluid to the washer bottle,
top up the oil ,
and the coolant.
Also check the E brake connection under the hand brake lever ( single brown wire to switch)it can work loose and cause a temporary light

Thanks Mrmerlin. I didn't know the washer fluid level would give you a warning. I'm pretty sure that bottle is empty as I've never used the washers. Hopefully, today I'll get the car out and see if adding the coolant fixed the problem. I'll post the results.
Mike

if you look in your owners manual it should list all of the warning lights that come on when you twist the key to the run position IIRC yours should have a washer fluid level

Right Again Mrmerlin. It's right here on Page 28...Washer Fluid "warning light comes on when level in the windshield / headlight washer reservoir is down to 2 U.S. quarts". I never realized it was there. The light is in the Coolant temp / Fuel level gage.
Thanks,
Mike

any of the warning lights that come on can trigger the I light,
then the original issue can stop the trigger when the fluid returns to its just enough level

Hi :)

Its not just fluid level warnings that can cause this...

I had exactly the same thing...master light came on but no other light to indicate which was causing it...

After a couple of weeks of it driving me nuts, my ABS light finally came on as well, which after a LOT of fault finding turned out to be one of the two ABS relays under the front wing....

So it COULD be ANY of the warning lights that come on when you turn on just the ignition....

And it may or may not be the coolant level ..... there is also a sensor for windscreen washer fluid level by the way...

All the best Brett :)

Thanks Brett ... very good information. Hopefully it was just the coolant level. It's been raining too much for me to check it out ... don't want to get the shark dirty:)
I'll post when I find out.
Thanks,
Mike

Usually the dash warning lights will burn out but the warning system still works.

IE a low coolant or washer may get left unattended for a while from a previous owner and the light may eventually burn out.
Since the new owner may not be aware of what the actual warning lights and positions should be,
the owners manual should be consulted,
this way you know what you should have VS what you do have .

Hi :)

Thats interesting as they DO have ABS in the UK in 82....

All the best Brett :)

Brett thanks for the additional info, are you sure about the ABS on an 82???

US didnt get ABS till, middle of 85.
IIRC it may have been an extra cost option as early as late 84 or early 85 for the US cars, but not 100% sure.
My early 86 5 speed US car has ABS.
my 84 Euro 928S with twin dizzys did not have ABS and it was an early 84.

My 86.5 auto had an ABS fault when I got it,
the CE panel relay was bad.
The ABS light came on when the key was turned on, fitting a new relay fixed this

Hi :)

My brother has an 84 S and he has ABS (in the UK) although it could have been special order...

I have had BOTH types of ABS faults at different times....

TYPE 1 .... ABS light came on with ignition and wouldn't go out ...was relay...

TYPE 2 ....ABS light came on after moving around 50 yards.... was sensor wire...





All the best Brett :)

Introduced in 84. (might have been std in Europe?)

USA option in 84 and 85.
USA standard in early 86.

Right around VIN XXX1000, ie, 86.5, system changed to axles with less tooth count and different electronics.


The 84 Euro we have here has antilock but triggers a warning. Am hoping Brett's experience with relay will help me.

If Stan's 84 Euro was sans antilock, that perhaps indicates it was ROW optional in 84.

The relay fixed my ABS light as well, but Brett, the 928 was the first Porsche to be offered with ABS and it was in '84..

I added coolant to the reservoir and bled the cooling system as instructed in the owners manual (did not need to add coolant after). Took the beast out and made a few "gentle" acceleration runs. Those runs did not cause the Central Warning light to come on. However a couple of WOT runs did turn the light on, AND the coolant temperature Light (at the top of the temp field) did come on. But only briefly. The engine coolant temperature was in the normal range. The COOLANT light at the bottom of the Coolant/Fuel Gage did not come on. That could be due to a burnt bulb, but I'm only guessing. I think I have a coolant system problem, but not sure what it is. Any ideas?

How does one "see" the windshield washer fluid level? All I can see is the filler neck, and through the fender well back to ???

Best regards,
Mike

Hi :)

On the washer fluid level....you CANNOT see it ever.... the bottle is under the inner wing behind the wheel shield and cannot be seen....and its HUGE , it contains around 2 gallons when full,,,, what you do is keep adding washer fluid and water to the filler neck .. until it overflows...
Then you know its full lol...

Hope this helps ..

All the best Brett :)

for the coolant i would first replace the heater control valve and the short hose this is a common failure point also replace the cap,
and inspect the bottle for cracks.

top off the fluid in the washer if you dont know if it will hold try filling with water first see if it holds .

As an aside to the washer tank try this,
remove the tank and remove the metal collars in the fill tube and the tank inlet then wash out the tank this will remove all of the rusty crud in the bottom of the tank so it wont plug your washer jets

I had my '83 checked at two shops - my alternator was going out and was the cause of the Central Warning Light flashing each time I accelerated from a stop. I replaced it with a Delco model today; seems fine now and gauge shows battery is getting charged (had been at zero)...

Thanks for the input, I'll keep plugging and let you know the results.
Mike

I continue to drive the beast, and push the cancel button on the Warning light when ever I accelerate! I filled the coolant tank to the very top thinking the sensor was located high in the tank. When I accelerate, the light at the top of the arc of the coolant temperature gage comes on and then the ! light comes on. When I stop accelerating or just reduce the acceleration the light turns off. The coolant temperature is showing normal or even a tad below normal temp. The coolant warning light at the bottom of the gage does not come on. Again, the engine runs great, but there must be something it's trying to tell me. Any more suggestions?:confused:
Mike

I would check the wires at the sender for the gauge, its quite possible that one of the connections is corroded or loose.
the gauge sender has 2 male pins sticking up . refresh the heat shrink on the female connectors

Thanks Merlin, I'll work on it today.
Mike

Sorry to revive this old thread, but I recently purchased this beautiful 82 from Mike, and this issue he was troubleshooting back in 2010 still exists. Since lots of experts were involved in this thread, I thought I'd ask again for any ideas.

To recap the issue, when accelerating briskly, and sometime when taking a turn quickly, the high temp warning light comes on and also triggers the central warning light. The needle on the temp gauge is in the normal zone. The High temp warning light goes off fairly quickly, and when you push the ! button, the central warning light goes off. I've also noticed that at highway speeds, the high temp light sometimes flickers a bit, which triggers the ! light, making me think maybe high speed air flowing through the front of the engine compartment is moving some wires around that may be shorting.

There is lots of talk in this thread about coolant level, but I don't see how that could trigger the high temp light.

I've checked the wiring and plugs to the temp sensor on the water bridge, but they look ok. I also had my son watch the light in the car while I wiggled wires all over the engine compartment trying to get the light to come on, but no luck.

I'm thinking swapping out the sensor might be a good next step. Haven't done a good ground cleaning yet, but need to. To confirm, the high temp warning light gets it's signal from the sensor near the water bridge correct? Is it direct, or is there some circuitry interpreting the signal that could be faulty? If it's the same sensor as on one of my other 928's, I'll just swap it out and test (86.5, 87 & 89).

swapping out the sensor is a good idea, they do go bad,

Note that there are 2 different sized connectors on the wires,
it is a good idea to swap in new connectors,solder them on.
radio shack has the both sizes of the female connectors.

NOTE also inspect the 14 pin connector and the engine side harness wires for shedding insulation the harness could be shorting .
spray deoxit onto all of the connections

Stan,

Thanks, I'll check the 14 pin and sensor connections. Have some deoxit as well. I can't quite figure out how acceleration triggers the issue though. The engine does rock when reved, so maybe there's enough engine movement during acceleration to move some bad wiring around, causing a short.

It was good to finally meet you at 3rd coast. I hope you will become a regular...

It was good to meet up at 3rd Coast.
Great people in the middle of the country.
its probably the 14 pin harness area that is causing the shorting look for shedding insulation,
NOTE this is a common fail point.

Don,
A tidbit that might assist you that I pulled from the WSM (90-29):

The Central warning system monitors the following functions:
1- Oil Pressure
2- Oil Level
3- Brake Circuit failure
4- Brake fluid level
5- Parking brake
6- Coolant Level
7- Coolant Temperature
8- Fuel Reserve
9- Washer Fluid level
10- Brake pad wear
11- Stop lights
12- Tail lights

Either a short/grounded wire or one of these systems is causing the warning.
BTW, the Single Component Test starts on 90-34 of the WSM. It is really very interesting.

John,

Every time the central warning light comes on, the high temp light comes on first, so I'm convinced it's only being triggered by the high temp warning light circuit, but the needle shows normal temps. I'll check out the test procedures.

Don,
I saw in the earlier posts what was happening. I am pretty sure that Stan got it right in the last part of post #35. Since the temp sensor wiring runs through the front engine harness, I would guess that somewhere in that circuit, a lack of insulation is causing the false (I presume) reading.