68 Cadillac MM Combo (Restore thread)

Ed... you almost have the lighting circuit correct, however, the power (+) goes to one side of the bulb holder, and the fixture is always live at the center of the socket, and insulated from the body of the car, unlike most of the other lighting in the car. There is a second wire that goes to the roof fixture that provides a path to ground through the door jamb switch. When the door is opened, the light is illuminated. The reason that this is important to know, is because some of the LED bulbs are polarity sensitive. This means that if you install them backwards, they will not illuminate. When this happens, you have to remove the bulb, and reinstall it 180 degrees from the way you have removed it. Simple thing to do, and you have a 50/50 chance of getting them installed correctly the first time.

The GE#68 bulb is a double contact bulb, and as such, the brass isn't part of the electrical circuit. It is important to know this, and to NOT install a single contact bulb into the socket. If you do put the wrong bulb into the socket, you will cause a direct short across the two terminals, and blow the fuse.
 

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Believe it or not there is a double contact bulb the grounds there the brass. I have a fist full of leds just that way. As i said people selling this stuff dont know what they are selling.

Asked one of them if they were 6 volt. They told me yes as long as you don't drop below 8 volts???
 
John ED Renstrom said:
Believe it or not there is a double contact bulb the grounds there the brass. I have a fist full of leds just that way. As i said people selling this stuff dont know what they are selling.

Asked one of them if they were 6 volt. They told me yes as long as you don't drop below 8 volts???
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Thats always an encouraging answer. I was recommended to use superbrightleds.com from one of the cadillac groups on facebook. Others seem to have had success with it. We will see, as they should arrive Friday, same day as my dome covers.
 
Used them before. I got all my 4 ft shop lights from them.out of the 50 we put in only one has failed in 3 years. But of course they are only the supplier not the builder. What i don't like is the completely different numbers. . Phillips has them numbered correct but at a price.
 
Yesterday my 4 bulbs came in along with my dome covers. Dome cover fit perfect and the bulbs also fit good and were double contact as Paul mentioned.

Only slight problem I have with these LEDs is it works fine on the rear, but the rest of the lights it seems a tiny bit loose. I think the contacts on the bulb itself are not quite as deep so it doesnt connect as firmly.

I am unsure if I can adjust the fixture itself or if it would be safe and feasible to solder a little bit of extra padding onto each contact (on the bulb, not the housing!)

Im open to suggestions, my wife suggested I stuff aluminum foil in there. I told her "no no no, theres two contacts so that will complete the circuit"
 
As long as they work, don't worry about the bulb being a little loose. If you spray the inside of the fixture with some white paint, it might brighten and even the light from the bulb.
 
Paul Steinberg said:
As long as they work, don't worry about the bulb being a little loose. If you spray the inside of the fixture with some white paint, it might brighten and even the light from the bulb.
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I forgot to mention the lights flicker a little as a result of the looseness, which made me a little concerned about fire risk. Thats the only reason I was thinking about padding it
 
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Insert a paper match into the side of the bulb to tighten it after you remove the sulfur end. That should tighten it if it is loose where the brass part connects. If it is the soldered end, then I have no suggestion, since if you put a dab of solder on the ends of the tips of the bulb, the heat might destroy the circuitry of the LED. The only way that you will know for certain is if you try it.
 
Paul Steinberg said:
Insert a paper match into the side of the bulb to tighten it after you remove the sulfur end. That should tighten it if it is loose where the brass part connects. If it is the soldered end, then I have no suggestion, since if you put a dab of solder on the ends of the tips of the bulb, the heat might destroy the circuitry of the LED. The only way that you will know for certain is if you try it.
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Good idea, I will give that a try this weekend. Thanks for the suggestion
 
Then check on the base of the socket. Some have a back o light base that twists in like the bulb and the get lose when you take it out. No risk for fire. If the socket is god it the switch. The led are low current draw and any interruption will make them flicker. Were the light would not.
 
I ended up taking all the LEDs out for the time being, since one of my lights the two springs began touching and melted so its now getting red hot. I will probably try to remove that fixture and see if I can repair it at all. I suppose worst case I can order another fixture now that I know where to find one, but will see what I can do.

In other news I drove to a new carwash yesterday called "IQ" because it has free vacuums, figured it would be a good way to suck up some of the broken glass under the seat and in the cracks of metal parts of the side of the bench (broken glass came with the car). It did work, got 95% of it up, however when pulling out from the place I noticed that I barely had any brake power, in fact the brakes did not even work until the pedal got to the floor, no pressure until the floor. And on the way down it hisses

I carefully got home, brakes did seem to work fine if I really mashed them on the floor hard, but it was far from safe. drove around the neighbor hood a little to test (see if its the same while braking while turning, pumping, etc)

The general consensus of several friends is that its likely a brake booster. So I called a local place that has done good for me several times on my other cars, and told them what I need and asked for a rough estimate, he made some called and called me back...he told me "that part is only available from the dealer".

I paused and said I'm not too sure a Cadillac dealership is going to have that laying around, but I'd do some checking. I laughed because who in their right mind would take this thing to a Cadillac dealership. I'm sure I can probably just find the part online cheaper and then just pay labor.

My question to you all here is does this appear to be the correct part?

https://www.partsgeek.com/catalog/1968/cadillac/commercial_chassis/brake/brake_booster.html

I know that just because it says it fits commercial that does not make it true.
 
Also it took me a bit after reading the shop manual to realize they refer to the booster as a power brake unit. I guess that terminology has changed over the years. Manual says it uses a Bendix or a Delco Moraine Single diaphram. Not sure which im using right now.
 
Brake Booster

Some rebuilders play loose with what fits what. If yours was working ok before I would have yours rebuilt .One source is below lots of other ones out there but I have used them before and always good work.

http://karpspb.com/
 
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Have you looked in the forum section "Recommended Vendors" for a rebuilder of power brakes. I am baffled why you would search the internet for a commercial chassis part, then ask friends and acquaintances where to get a part, etc., when you have the very best resource at your finger tips right here. I guess that this once again proves the adage,

"You can bring the horse to water, but you can't make him drink" :beatdeadhorse5:

http://professionalcarsociety.org/forums/showthread.php?t=807
 
Paul Steinberg said:
Have you looked in the forum section "Recommended Vendors" for a rebuilder of power brakes. I am baffled why you would search the internet for a commercial chassis part, then ask friends and acquaintances where to get a part, etc., when you have the very best resource at your finger tips right here. I guess that this once again proves the adage,

"You can bring the horse to water, but you can't make him drink" :beatdeadhorse5:

http://professionalcarsociety.org/forums/showthread.php?t=807
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When theres a fence around the water the horse cant drink. I've been told about that section of the forum in the past but I do not have access to it. It seems I CAN access that direct link to the Power Brake topic, but I cannot access the forum section itself. Probably because I am not yet a member. Will certainly look into that once I get the part off.

The reason I asked people is because I was utilizing the resources I had access to at the time (this forum, a cadillac fb group, and a mechanic friend)
 
First check is the master cylinder full? Second check foes the booster have vacuum?. Third check is does it hold vacuum?

You need to find out what happened before you start spending money. Always suspect a vacuum hose on a old car as the problem. The best tune up you can do is replace all of them. If the booster is getting vacuum and its holding vacuum it should be good. With the engine running pull the check valve out of the rubber grommet. The booster should suck air in. If you come up with the hose in your hand it was not attached to the engine. check the simple thing first.


As for the light the power connection is grounding out. You most likely broke the insulater out removing or replacing it. It happens or you have a bulb that grounds threw the side. Don't ask me what they fit but i have a few leds like that here. As you are not having a issue with it out I would say wrong bulb.

And the norse to water thing your right about the fence. But i was always told if if you tie there head to the trough long enough they will get thirsty. In your case its a gate post.
 
Cylinder is full, no loss of fluid. Did some troubleshooting last night

No leaks on the hose, check valve or manifold inlet. Did a visual check followed by a soapy water test and no bubbles (yes while idling).

Also followed some troubleshooting steps for testing the pedal. I let the engine idle a few minutes, then shut it off and pressed the brake 4 times, holding the pedal down slightly the final time while starting the engine. When I start the engine the pedal goes to the floor. (guide I looked at said it should only go down about an inch when the engine is started.)

I didnt remove the check valve yet. May try that tonight if I still have light after mowing
 
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