3 Turbos

rear backup/reverse lite voltage.

Here it is. I have to connect a GPS/DVD/Camera system to my 87 951.

I have to connect a wire to the "positive/hot" side of my parking brake. What is the voltage at the "positive/hot" side of the parking brake switch when the parking is "set?"

I also have to connect a wire to the "positive/hot" side of the rear backup/reverse lite. What is the voltage when the lite is on.

When I have the key on without the engine running, I can't get the backup/reverse lite to come on. Does the engine have to be running for it to be on??

I'm trying to finish my install. Would appreciate any info/feedback that I can get.

Thanks!, Steve

Charlotte944

Why do you have to tie into the parking brake and back-up lights? This sounds totally wrong to me. I can't imagine a situation where a GPS/DVD/Camera whould need to know if the back-up lights were on or if the parking brake was set.

Charlotte944

Oh, the back-up lights should come on whenever the key is on and the transmission is in reverse. The back-up light switch is on the passenger side of the gear box, just forward and above the output shaft.

Sam Lin

Parking brake signal is to prevent viewing video or changing nav settings while the car is moving, it's a legal requirement. Backup light signal is to automatically switch to the reverse camera when the car is put into reverse.

Voltage should be 12V to both signals, but you need to be careful to watch out how much current you try to pull. I'm not sure, but I think the engine does indeed have to be running for the reverse lights.

Sam

Charlotte944

OK, NOW I get it.

I guess I've been out of the auto electronics loop for too long!

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Sam,

It' is a mainly a DE car were I don't use the parking brake after coming in from a DE session. So I would like full functionality of the system witout having to put on the parking brake.

Am I to assume that buy connecting this wire "in question" to the "hotside" of the parking brake switch as per instruction, that this "wire" requires to see a voltage of +12V to "fool" the GPS/DVD/Camera system circuit into thinking the parking brake is on?

If you cannot answer online, please do so offline, as this might be a sensitive issue. Please answer if you know the answer, or anyone else for that matter. Trying to finish install before my trek out to Road America.

Thanks, Steve

Sam Lin

Do what we all do (did I just say that?) - as you suggest, just wire it to a 12V switched power source.

Sam

Sam Lin

Oh, and our parking brakes are an internal drum, specifically designed to allow even cooling of the rotor even when applied. It's fine to use them on hot brakes right off the track - I do it all the time. That's actually the main reason for their design.

Sam

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Just to clarify, should it be "switched +12V" or should it be "non switched - always hot"

Thanks Again! Steve

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I've never heard that before. Are you sure the shoes on the drum won't stick from extreme heat?? The rotors may cool down faster because of the extra heat sink fronm the drum/shoe combo, but I would think that they would somehow cause problems if your rotors are REALLY HOT!??

Steve

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One more question. I also need to connect a wire to a "car speed signal". My mechanic thinks that you can take the signal off the back of the dash where the stock speedometer gets its signal input. Can that signal be "had" somewhere down the line without taking the dash out?

Thanks Again!, Steve

Sam Lin

I would wire the parking brake signal to a switched 12V, rationale being you don't need the functionality when the car's off, and the unit'd be off at that time anyway - it's just wasting that little bit of power.

I've used the parking brake on this car and on the Vette (newer Vettes all use similar design for the same reason) hot off the track (of course there was a cooldown lap, so not REALLY HOT) with no issues. It's not really an issue of cooling faster or slower, just the drum design allows even cooling so no warpage, while holding your car in place.

Car speed I'm afraid the only one I know of is the blue/red stripe speed out the back of the gauge cluster, it's at the top of the vertical "B" plug on the right. I'm sure there's gotta be something around the DME/KLR, but I've not had time to look there. Gauge cluster removal is 5 minutes, don't worry.

Sam

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Thanks Sam!

I have an 87 951 with an air bag. Do you think I have to pull the steering wheel off or do you think I'll be able to get the dash out with the wheel on. If I do have to take the steering wheel off, how do you get the air bag off?

Thanks Again!

Steve

Jon Moeller

Steve,
Sam asked that I follow up. On the airbag cars, removing the gauge cluster can be done without removing the steering wheel.

Pull the surround for the gauge cluster by removing the phillips head screws that hold it to the dash. There are quite a few of these, so be gentle when trying to pull it out, you may have forgotten one or two. The whole unit shifts out to the right, and needs to be compressed somewhat to clear the steering column (It's plastic, so you have tons of give).

Then, remove the 4 cad-plated phillips screws that hold the cluster itself in the dash. Ease the cluster out of the dash, and unclip the 3 ribbon wire connectors that lock into the back of the cluster. That should pretty much cover it.

If you decide that you need more clearance, the airbag comes off with two torx screws, one on each side. Then, a 30 mm (?) nut on the steering shaft needs to be removed, before the wheel slides right off. (If you do this, make certain that you mark the orientation of the wheel relative to the column before removing the wheel.)

-Jon

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Jon and Sam,

Thanks so much for all your responses! I think I'll try the instrument cluster removal without removing the airbag/steering wheel. If worse comes to worse, I'll remove the airbag/steering wheel, but I'll try the simpler way first.

Sam, thanks again to have Jon (and thank you too Jon) answer my questions. It has helped alot!!!

Steve