More Central Warning system questions.
10-27-2010, 09:39 PM
#1
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More Central Warning system questions.
Quick question:
Still battling the Central Warning system on my '83 5-speed.
I had thought the blinking warning that occurs after the motor wams up was caused by a faulty oil pressure sensor, and the reason I did not see that particular indicator was probably a bad dash light. Tonight I hunted around with a flashlight in an attempt to see the wording, but its not there. Instead there is an antilock brake indicator, and this never lights up.
I only have the first release of the service manuals, which cover up to model year 82, not 83. Does the '83S not have an "oil pressure" warning light, relying on the gauge instead? Does the '83 have antilock brakes? If my model does not have them, is this why the indicator does not come on in the ignition-on key position?
The oil pressure gauge appears to work normally, sitting at full scale when running. Don't want to buy a new sensor if I'm not sure the old one is faulty.
Thanks,
Rick
Still battling the Central Warning system on my '83 5-speed.
I had thought the blinking warning that occurs after the motor wams up was caused by a faulty oil pressure sensor, and the reason I did not see that particular indicator was probably a bad dash light. Tonight I hunted around with a flashlight in an attempt to see the wording, but its not there. Instead there is an antilock brake indicator, and this never lights up.
I only have the first release of the service manuals, which cover up to model year 82, not 83. Does the '83S not have an "oil pressure" warning light, relying on the gauge instead? Does the '83 have antilock brakes? If my model does not have them, is this why the indicator does not come on in the ignition-on key position?
The oil pressure gauge appears to work normally, sitting at full scale when running. Don't want to buy a new sensor if I'm not sure the old one is faulty.
Thanks,
Rick
10-28-2010, 01:23 PM
#4
Rennlist Member
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Another possible cause for a blinking ! light is the brake pressure warning. The brake light switches also monitor the brke pressure in the two systems, and switch failure is not uncommon.
Up thru 1983, the brake lights are operated by twin pressure switches on the bottom of the brake master cylinder. From 1984 - up, the brake lights are operated by a simple plunger switch mounted on the brake pedal under the dash.
The earlier brake light switches do double-duty, operating both the brake lights and the brake pressure warning signal. These switches can cause some problems.
The switches are identical - one in each hydraulic circuit. They are single-pole, double-throw switches. This means that you have only one circuit (single pole) thru each switch, and that the switch chooses one of two outputs (double throw).
Each switch has three connections
ower, central warning computer, and brake light.
Not Activated
There is a power feed into each switch. When the switch is not activated (no pressure in the brake circuit) the power isn't hooked to anything.
When the switch is not activated, the central warning computer and the brake lights are connected inside the switch. Nothing happens, since there is no power applied on either circuit.
Activated
When the switch is activated by brake hydraulic pressure in one of the circuits, the central warning computer connection is broken, and the brake lights are hooked to the power feed. This removes the central warning computer from the circuit, and puts power on the brake lights.
(This might be easier to visualize if you think of three wires: one for 12 vdc, one to the brake lights and one to the warning computer. The lead that goes to the brake lights is connected to the one to the warning computer until brake pressure pushes it off of that wire and over to the one going to power.)
All three leads go to both switches.
When you apply the brakes, both switches should activate. Both switches disconnect the warning computer and connect the power to the brake lights. The brake lights come on, and no signal is sent to the warning computer, so it is happy.
If only one switch activates (either no pressure on one side of the brakes, or a bad switch), then things change.
On the switch that is not activated, the brake light circuit is still hooked to the warning computer.
On the switch that activates, the brake light circuit is hooked to 12 vdc.
The brake lights come on.
In addition, power flows on the brake light circuit back to the non-activated switch. Since in this switch the brake light circuit and warning computer are hooked together, 12 vdc is applied to the warning computer circuit. This set the Brake Pressure Warning light.
If you have a bad brake light switch, I strongly suggest that you replace both switches.
(P/N 113 945 515 G)
Up thru 1983, the brake lights are operated by twin pressure switches on the bottom of the brake master cylinder. From 1984 - up, the brake lights are operated by a simple plunger switch mounted on the brake pedal under the dash.
The earlier brake light switches do double-duty, operating both the brake lights and the brake pressure warning signal. These switches can cause some problems.
The switches are identical - one in each hydraulic circuit. They are single-pole, double-throw switches. This means that you have only one circuit (single pole) thru each switch, and that the switch chooses one of two outputs (double throw).
Each switch has three connections
ower, central warning computer, and brake light.Not Activated
There is a power feed into each switch. When the switch is not activated (no pressure in the brake circuit) the power isn't hooked to anything.
When the switch is not activated, the central warning computer and the brake lights are connected inside the switch. Nothing happens, since there is no power applied on either circuit.
Activated
When the switch is activated by brake hydraulic pressure in one of the circuits, the central warning computer connection is broken, and the brake lights are hooked to the power feed. This removes the central warning computer from the circuit, and puts power on the brake lights.
(This might be easier to visualize if you think of three wires: one for 12 vdc, one to the brake lights and one to the warning computer. The lead that goes to the brake lights is connected to the one to the warning computer until brake pressure pushes it off of that wire and over to the one going to power.)
All three leads go to both switches.
When you apply the brakes, both switches should activate. Both switches disconnect the warning computer and connect the power to the brake lights. The brake lights come on, and no signal is sent to the warning computer, so it is happy.
If only one switch activates (either no pressure on one side of the brakes, or a bad switch), then things change.
On the switch that is not activated, the brake light circuit is still hooked to the warning computer.
On the switch that activates, the brake light circuit is hooked to 12 vdc.
The brake lights come on.
In addition, power flows on the brake light circuit back to the non-activated switch. Since in this switch the brake light circuit and warning computer are hooked together, 12 vdc is applied to the warning computer circuit. This set the Brake Pressure Warning light.
If you have a bad brake light switch, I strongly suggest that you replace both switches.
(P/N 113 945 515 G)
10-28-2010, 02:06 PM
#5
Team Owner
Nice writeup Wally!
thanks, Stan
thanks, Stan
