Where does parking brake release get vacuum from? ('75 Eldorado)

[benji808]

Automatic parking brake release doesn't work. I traced the black-with-red-stripe vacuum hose to the passenger side of the car where it appears to go into a box with a bunch of climate control hoses. I do not see any other vacuum hoses coming out of the firewall that I have not identified as being for some other purpose (antennae and heater on the passenger side, cruise control brake shut-off and more climate stuff on the driver's side). The hose seems in fine condition, but I don't register any vacuum from it when shifting into gear...I think it's supposed to "suck up" the parking brake release thing which pulls the handle.

Any thoughts on how to troubleshoot this?

[TJ Hopland]

I don't remember if it was on my 75 or 78 but I do remember thinking it was tied to the climate control source on at least one of those cars.  Does the climate control sort of work so its got vacuum?  I only remember this because one of the two systems was broken and I just thought no point in hooking this line back to the engine but then the other system wasn't working either and I needed that to work.

Again just fuzzy memories here but I'm thinking on the 75 the vacuum like source for that is kinda in the middle of the firewall and on the 78 it was way over on the drivers side...  again fuzzy memory talking here so if that doesn't look right its probably not.

[benji808]

It does seem to be hooked into the climate system. Climate system seems to blow air out of the correct vents, so it seems weird that I'm not getting vacuum out of that  parking brake hose. Hmmm.....

["Cadillac Kid" Greg Surfas 15364]

You will only get vacuum when the car is placed in "D"  or "R". That is if the neutral safety switch is functioning correctly.
Greg Surfas

[benji808]

I checked that - didn't get vacuum in R or D. What/where is the neutral safety switch?

[The Tassie Devil(le)]

On top of the steering column, inside the cabin, just back from the firewall.   It is held in place by a single clamp that goes under and around the column.

Bruce.

[benji808]

I found it! Looking in the shop manual it appears that this has three functions:
1) Turns on back-up lights in reverse
2) Locks doors in drive
3) Vacuum to automatically release parking brake

Initial inspection shows that the back-up lights do come on in reverse, the door lock terminals are unplugged (would love to find them sometime, because that would be cool). The parking brake release vacuum lines appear to be in good shape and plugged in appropriately.

Is there anything I can do to troubleshoot the unit itself? I may spend a bit more time tracing the hoses tomorrow.

Thank you!
Benjamin

[cadillacmike68]

The line goes to a vacuum manifold (at least through 1970 ) which is up on the firewall, or another primary vacuum source. Make sure the line from the NSS goes to Somewhere that is a vacuum source. If the line is disconnected or wrongly connected, then there is is No Way vacuum will go to the pull off.

[benji808]

A couple updates here:

1) I was wrong about where the vacuum hose from the vacuum release - Greg and Bruce were correct - it runs into the safety switch, not the climate system (that was a DIFFERENT black-with-red-stripe hose lol).

2) I am getting vacuum to the switch, but no vacuum, out when I shift gears, so I'm assuming that part of the switch is bad. I may follow this guy's tutorial and see if I can fix it myself: https://www.youtube.com/watch?v=kURiDTeRCds

3)  I'm trying to find my automatic door lock wires (they are not plugged in to the safety switch). Does anyone have any information on where they come from, and/or what color they were from factory?

Thanks!

[benji808]

I successfully repaired the neutral safety switch following this video from one of the Chicago clubs. Only thing I really did differently was to use M2.5 nuts and bolts to close it back up, rather than rivets: https://www.youtube.com/watch?v=kURiDTeRCds

Fairly simple, and I now have vacuum getting to the release diaphragm. It does appear that the diaphragm is leaking, so replacing that is next up for this project. Getting closer!

If anyone has a '75/'76 (maybe '71-'74) with doors that automatically lock when shifting to drive, I would be very interested to see your wiring setup off the safety switch...I'm not finding wires that I think would go there, so wondering if they were removed, or if my model didn't have the feature. 

[TJ Hopland]

I have never seen the door lock feature unless it often fails or has been disconnected by the time I saw the cars.

[benji808]

Fair enough - that's what I'm hearing from most people, so I'll likely let it go (although I'm thinking it wouldn't be hard to hack it...I think just need power constant into the safety switch and then a line out to the lock feature...maybe some day  )

[1776-1976-Eldo]

I have never seen the door lock feature unless it often fails or has been disconnected by the time I saw the cars.

I have working auto door locks and a working brake release, I will see what info I can provide.

[benji808]

Neat! I would be interested to know what the setup was...I know how the switch works - just a simple sliding metal piece that bridges a connection when going into gear, so I assume that you have a plug with power going into the safety switch, and then a wire coming out that connects with the door lock trigger somewhere.

[TJ Hopland]

It would be the same time the parking brake releases so maybe a vacuum switch?

[76Caddy]

I believe the the automictic door lock feature was a new option for 1976 models (except for the '57-'58 Eldorado Broughams).

Tim

[Roger Zimmermann]

I believe the the automictic door lock feature was a new option for 1976 models (except for the '57-'58 Eldorado Broughams).

 

Tim, the '57-'58 Broughams had this feature only at the rear doors, disconnecting the interior handle. When locked with the gear lever in Drive, the rear doors could be  opened with the exterior handle.