Electrical Gremlin

ahklein · ahklein's Garage

My 73.5 T Targa recently started a dash-light gremlin. For as long as I owned the car, if my handbrake was up while the engine was running, the buzzer would sound and both turn signal indicators would glow, as would the red light on the top of the oil pressure/temp guage. Now, these occur regardless of the handbrake position. I assumed it was a shorted out switch. I disconnected the wires from the handbrake, but it is unchanged.

Anyone have any thoughts?

Thank you!

steely · 11-23-2010, 04:39 PM

what are the turn signals doing when this happens (outboard)?
any change if you use the turn signal? open the door?
and now it happens when you drive?

Bob Kontak · Bob Kontak's Garage

Speculating here but I am seeing a connection amongst the components. I am a novice, but actually pretty slow in thinking.

Let's pretend the e brake switch was still connected and the problem only occurred when you pulled the e brake lever.

I see the following connections:

The seat belt warning light and buzzer are wired to the e-brake switch.

The e brake switch is connected to the oil temp/idiot light gauge
The e brake light is fed from the oil temp/idiot light gauge

The "Turn Signal / Emergency Flasher Unit" is connected to the same e-brake switch and e-brake light connection in the oil temp/idiot light gauge (but travels thru a bulb first)

The connection on the Flasher Unit (I am thinking this is the relay) also travels to the Emergency Flasher Switch.

I think that lifting the e-brake should normally kill the seat belt buzzer and seat belt light. How it does it I don't know - through the connection between e brake switch and the seat belt light somehow.

Here is my layman's theory. In the e brake switch, something was wrong - wires backwards or switch defective in a harmful way. When you lifted the e-brake you actually fed the seat belt warning system juice and / or the belt warning system fed the e-brake indicator system juice (along with the oil gauge and the flasher system). I think the flasher relay is cooked.

Here is a question: Did the seat belt warning system work (through your ownership) with the e brake in the off position?

ossiblue · 11-23-2010, 05:22 PM

The handbrake switch is a switch to ground. When working properly, pulling up on the hand brake grounds the circuit causing the red light in the gauge to blink as the power comes from circuit track 40 from the flasher relay. You state the light glows, which I read to mean a steady light, and continues after the ground switch (handbrake switch) was disconnected. I'd suspect a problem with the flasher relay as it also feeds the turn indicator lights in the gauge and they are lit also. Try swapping out a know good one and see if that cures your problem.

Note, you also have a warning switch (also a ground switch) in your master cylinder that's wired to the dash gauge red light. Take a look at the wiring diagram for the 73.5 on this site's home page ( click on "Welcome" tab at top of this page, look on the left side of page that pops up, click on Elec. Diagrams) to help track down this gremlin.

Bob Kontak · Bob Kontak's Garage

I hear you on the switch to ground but how do we account for the seat belt buzzer?

Edit - I am thinking out loud with that comment - not challenging.

steely · 06:56 PM

I admit not being familiar with 73's and I agree it could be related to the flasher - I was hoping to get more clues from the questions I asked.

major spit ballin follows.

I could be wrong, but I think the buzzer may just be a door-open buzzer - starting with the key/ign (sig 51 on buzzer 53) and held until the door switches close.(?) My seat belts just have a light. on edit: this still doesn't answer Bob's question.

The turn sig lites glow if they have a return thru the flasher that shouldn't be there (and no flash in this case) and why I wondered (shotgun) about the state of the outboard TS lites. I didn't get a chance to tie the "oil" lite and e-brake sw to it all. Suspect the flasher is on the hairy edge and the slight change in gnd by the e-switch was enough.

on further edit: I don't think the signals themselves would lite since the ts sw blocks this path when it is in the off position.

E Sully · E Sully's Garage

Bob Kontak · Bob Kontak's Garage

Quote:

Originally Posted by steely

I was hoping to get more clues from the questions I asked.

Yes, we need some feed back from the OP.

Here is part of the diagram. Note the connection between the e brake switch and the seat belt buzzer.

I don't know what the yellow wire does but it is the only connection to the buzzer I can find in the drawings. I thought the yellow wire may kill the buzzer and light if you lift the handbrake.

Bob Kontak · Bob Kontak's Garage

E Sully - Thanks - That is the whole shooting match.

ahklein · ahklein's Garage

Thank you all for your thoughtful replies.

When I use either turn signal or 4-way flashers, the buzzer immediately goes out, and the turn signal indicator acts normally (One side flashes, other side goes out. Same when I use the 4-way flashers). Buzzer and green TS indicators returns as soon as TS or 4-ways are off.

The turn signals work properly.

I have since disconnected the wiring plug from the bottom of the e-brake handle. Now the buzzer and turn signal indicators are the same, but the red light is non-functional.

I have owned this car for 7 months, and in the past I only heard the buzzer when the ebake was up. I believe the seat belt triggers for the buzzer had already been disconnected.

Any additional thoughts?

Bob Kontak · Bob Kontak's Garage

I would start simple. Find the buzzer and make sure the red and black wire is on connection 15, yellow and red wire is on 50a and the white and black wire is on 86.

Also, determine where the seat belt system has been disabled.

I have the diagrams and can e-mail you if you private message me your address.

ossiblue · 11-24-2010, 09:43 AM

You may have two problems, one with buzzer circuit and the other the flasher relay. I only suggest the flasher relay because it is the common power source for the brake warning light and the turn signal lights. Disconnecting the ground for the handbrake has turned off the brake warning light as expected so that switch is probably not the problem. The fact the turn signal lights remain on make me suspect the relay.

As for the buzzer, it may be a fault in the ignition switch, the buzzer itself, or the seat/seat belt switches. I would explore the connections/wires to the seats and seat belt switches first, as Bob suggested--these are easiest to access. The buzzer is constantly "hot" but the ground which sets off the sound comes from either the ignition switch, position 1 I believe, and the grounds from the seat/seat belts. Let us know what you find.

Bob Kontak · Bob Kontak's Garage

Is the red light on top of the oil pressure / temp gauge the e-brake light? I bet it is. I was thinking it was the oil pressure idiot light ahklein was talking about in the first post.

ossiblue · 11-24-2010, 04:30 PM

Quote:

Originally Posted by Bob Kontak

Is the red light on top of the oil pressure / temp gauge the e-brake light? I bet it is. I was thinking it was the oil pressure idiot light ahklein was talking about in the first post.

Yes, the red light on top of the oil pressure/temp gauge is the brake warning light on a 73.5. When working properly, it should blink when the handbrake is raised, not glow steadily. That's another reason to suspect the flasher relay.

ahklein · ahklein's Garage

Any thoughts on getting to the flasher relay? On my car I can hear the relay, but it seems to be covered by a plastic shield and the ventilation fan. Do I have to remove this entire panel to access the relay on the drivers side?

E Sully · E Sully's Garage

You can get to it by removing the speedo or tach.

ossiblue · 11-25-2010, 06:45 AM

Quote:

Originally Posted by E Sully

You can get to it by removing the speedo or tach.

Actually, it's easiest to reach by removing the gas gauge as it sits directly in front of the hole for the gauge, once it's removed. Hint: open the trunk to allow some light (you can even remove the cardboard cover) to easily see the relay, especially for replacement.

Bob Kontak · Bob Kontak's Garage

I don't have carpet in my 81 trunk and can reach in from the trunk on the outboard side of the master cylinder and access the part.

http://www.pelicanparts.com/cgi-bin/smart/more_info.cgi?pn=914-618-303-11-M44&catalog_description=Hazard%20Flasher%2FBlinker%20R elay%2C%20911%20%281969-84%29%2C%20Each

ahklein · ahklein's Garage

I replaced the Flasher relay and now the buzzer off, but the red light above the oil pressure/temp Gage flashes red. Also, the relay is "going crazy"

Turn signal indicators work while TS is activated, but not with 4 ways.

Any thoughts?

ossiblue · 12-04-2010, 01:04 PM

Quote:

Originally Posted by ahklein

I replaced the Flasher relay and now the buzzer off, but the red light above the oil pressure/temp Gage flashes red. Also, the relay is "going crazy"

Turn signal indicators work while TS is activated, but not with 4 ways.

Any thoughts?

Thoughts? Yes, the system is now working properly in that the dash light is blinking and, of course, the relay is clicking. What is not proper is that it is working when it shouldn't. Since the relay is now known to be good, something is apparently activating the brake light warning circuit. Have you checked the brake warning switch on the master cylinder?