Author Topic: 1968 DeVille Convertible - Restoration  (Read 16033 times)

Offline DeVille68

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  • Name: Nicolas Hubacher
Re: 1968 DeVille Convertible - Restoration
« Reply #140 on: March 27, 2017, 02:56:36 PM »
Hello guys

Not too much progress in the last weeks but I managed to completely wet sand, puff and wax the car. It now looks way better.
But unfortunately I now know every rust bubble and imperfection! And there are a lot of tiny imperfections. Damn...some day I might need to repaint the car...but that shall wait another 5 years!

So, otherwise I completed the restoration of my vacuum system. It is all fixed and leak free. Exept for the power brake booster.
I did put the A/C dash control back into the dash and startet the calibration as outlined in Tim's manual.

But something I must do wrong.
I says to disconnect the dash interior temperature sensor. Then to jump the yellow to green wire on the amplifier connector with a 150 ohm resistor. Then the voltage to the transducer (black and white wire) should be about 6V

Well, I measure 12.9 V!! (to ground)
The yellow wire (power supply) has about 12.97 - 13 V.   (to ground, that is batterie voltage)

When I measure the resistance on the amplifier I measure (between the two terminals) I get about 160ohms (ignition off) but I measure about 650 ohms when the ignition is on.

When I plug all the sensors back in I measure about 180 ohms. But still the voltage is way off. (around 12 V)

So then you should be able to hold the potentiometer with a screw driver and move the temperature dial until you get 6V. Well I can set the dial completely to max (with no travel on the potentiometer left) or to full cold. And the voltage at the transducer only varies by about 0.4V, still being around 12V.

I must be doing something wrong?
Any ideas?
Should I remove the A/C Dash unit again and test it on the bench? How could I do that?

Thanks!
Best regards,
Nicolas
« Last Edit: March 28, 2017, 02:54:13 PM by DeVille68 »
1968 Cadillac DeVille Convertible (silver pine green)

Offline 6262

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  • Name: Nils Burkert
Re: 1968 DeVille Convertible - Restoration
« Reply #141 on: March 29, 2017, 07:00:01 AM »
Nicolas, is there no woodgrain on your dash? Is this standard for the De Ville convertible?
« Last Edit: March 29, 2017, 07:03:09 AM by 6262 »

Offline DeVille68

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Re: 1968 DeVille Convertible - Restoration
« Reply #142 on: March 29, 2017, 08:32:26 AM »
Nicolas, is there no woodgrain on your dash? Is this standard for the De Ville convertible?

Hi, no a DeVille Convertible has real rosewood veneer as standard (because it has leather as standard).

But, mine was cracked and in bad shape, hence I sanded the wood and sprayed new clear coat on it.
Refer to
post http://forums.cadillaclasalleclub.org/index.php?topic=130360.msg334363#msg334363
so see the restored wood veneer.


The Calais only had cloth inserts and a brushed aluminum instrument panel insert. (I think it is aluminum?)
The standard DeVille (closed car) had no wood when outfitted with cloth.
If the optional leather was ordered, then it would also receive the rosewood veneer on the doors and in the instrument panel.

--> Detailed information can be found in the data book of this year (available on the gm heritage website).

Best regards,
Nicolas
1968 Cadillac DeVille Convertible (silver pine green)

Offline DeVille68

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  • Name: Nicolas Hubacher
Re: 1968 DeVille Convertible - Restoration
« Reply #143 on: March 29, 2017, 02:04:28 PM »
I refer again to my post about the A/C amplifier board.

So suddenly, I realized that my problem of measuring about 12V at the transducer wire (black and white) could be of a miss calibrated vent switch. I checked that the switch only sends 12V in vent or off position and sends 12V to the violet wire (which then goes the compressor clutch) only when the lever is in lo, auto, hi, fog, ice position. Also the lever should be in the auto modus for making this temperature dial adjusment.

So, the switches on the unit are not my problem. I even disconnected them - no difference at all.

What is strange is, that when I measure the resistance of the potentiometer of the temperature dial I measure reasonable values when the ignition if of.
I measure between 100 ohm and 850 ohm.

But as soon as I switch on the ignition I measure -200ohm or open loop. Very strange. I do not understand this.

How can I measure and verify the amplifier on the bench?


Best regards,
Nicolas
1968 Cadillac DeVille Convertible (silver pine green)

Offline 6262

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  • Name: Nils Burkert
Re: 1968 DeVille Convertible - Restoration
« Reply #144 on: March 30, 2017, 12:11:43 PM »
Hi, no a DeVille Convertible has real rosewood veneer as standard (because it has leather as standard).

But, mine was cracked and in bad shape, hence I sanded the wood and sprayed new clear coat on it.
Refer to
post http://forums.cadillaclasalleclub.org/index.php?topic=130360.msg334363#msg334363
so see the restored wood veneer.


The Calais only had cloth inserts and a brushed aluminum instrument panel insert. (I think it is aluminum?)
The standard DeVille (closed car) had no wood when outfitted with cloth.
If the optional leather was ordered, then it would also receive the rosewood veneer on the doors and in the instrument panel.

--> Detailed information can be found in the data book of this year (available on the gm heritage website).

Best regards,
Nicolas

Nicolas, thanks for the extensive answer. I have been following your thread from the beginning and know about your efforts on the wood veneer. It was the attached picture which got me thinking. I did not recognize that it was taken before the re-application of the veneer. Therefore I assumed you had left it out with good reason.


Offline DeVille68

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Re: 1968 DeVille Convertible - Restoration
« Reply #145 on: April 01, 2017, 02:09:51 AM »
Hi Nils

Ah, oke. Very good. Thanks for reading my thread. I hope it helps others with the same restoration jobs. Or that it is just interesting to read. I myself read other restoration blog too, just because I think it is interesting.
I will add some more content over the next few weeks.

Best regards,
Nicolas
1968 Cadillac DeVille Convertible (silver pine green)

Offline DeVille68

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Re: 1968 DeVille Convertible - Restoration
« Reply #146 on: April 09, 2017, 08:43:23 AM »
So my mistake was that I did not check for proper ground at the transducer. There is a insulation material with a quite big "bulge" with some more insulation material stuffed in it.

I accidentally but some screws in for mounting the transducer and I wanted to just mount it loosely to be able to calibrate it.
Well by putting it in loosely I accidentally screwed into the insulation material making no ground connection of course.

So, what I measured with my multimeter was basically the voltage drop across the multimeter itself. Since it has very high ohm a very very small current was flowing giving almost no voltage drop.

I then mounted the transducer correctly and now the amplifier along with all the sensors and temperature dial works perfectly.


One last issue that I have is with my rebuild vacuum valve. It lets a small amount of vacuum by in the vent position. Somehow the planes are still not perfectly flat. When holding the valve against a light source I can see a little light coming through, but only on the perimeter. Hope I can sand the valve half some more...
1968 Cadillac DeVille Convertible (silver pine green)

Offline DeVille68

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Re: 1968 DeVille Convertible - Restoration
« Reply #147 on: May 11, 2017, 03:02:54 PM »
A little update:
- Since I grounded the transducer the mixing of heat and cold worked fine. I adjusted the voltage at the transducer according to Tim's manual.
- However, the blower would only work in A/C mode. (dial turned to 60)
- The reason was the power servo on the firewall. I had to resurface the valve again. I did this before but apparently not good enough. This time I used a 5000er grid wet sand paper and a piece of glass such that I had an absolute flat surface. I checked the surface of the valve halfs against the light using a straight edge.
- After that I replaced the rubber insulation around the base of the power servo.
- Now everything seems to be vacuum tight.

- To be able to test the system without running the engine (ignition not yet reinstalled) I used an external vacuum pump. However the blower would still only work in A/C mode. Until I realized that the heat sensitive valve in the heater valve is still open thinking that the engine water was still cold, and hence not allowing the vacuum blower switch to close. So I heated the valve a bit with my heat gun and voila everything works now. All flaps and all blower settings.



Since I already removed the dash, radio and ducting I decided to replace the insulation on the dash and firewall. I also glued new rubber around the A/C outlets on the ducting. Here are some pictures.

The last picture shows the new insulation. It is a special glass fiber material with an aluminum foil on one side. I did glue two or three sheets together. 
1968 Cadillac DeVille Convertible (silver pine green)

Offline DeVille68

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Re: 1968 DeVille Convertible - Restoration
« Reply #148 on: May 11, 2017, 03:07:42 PM »
Found some factory markings!

1) On the passenger floor pan under the carpet under the dash - there is a large yellow "A"

2) On the insulation of the firewall under the dash. There is rubber molded piece that holds a pocket of insulation material against the firewall. On its side there is a large yellow "29"

1968 Cadillac DeVille Convertible (silver pine green)

Offline DeVille68

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Re: 1968 DeVille Convertible - Restoration
« Reply #149 on: June 21, 2017, 02:17:54 PM »
wow, how time goes by!  Haven't posted any progress in a while.

Since May I have finished the A/C restoration, the car drives again. Had to repair the kick down switch (I will write something later about this). Had the repair the heat riser valve. The replacement unit is well made but something with the spring rate or weight does not match. Have to make some adjustments.

I also studied and totally rebuild the ignition system, new plugs, new wires, new condensers all around.
An advice to all: change your condensers! I have measured them using a proper capacity measurement device and they were only about 10%-15% lower than the rated capacity, but now with new ones (about 5% higher) I have a totally clear radio signal!

One question about the ignition system:
I have a later model HEI ignition system (do not know from which year)
But it seems that the centrifugal advance does not advance far enough.

The information in the show manual tells me that at 2000 rpm I need between 29 and 33 degree of advance at the crank.
The vacuum needs to be 0 at 8'' and between 22.60 and 25.20 at 14'' vacuum. (in degree of crank)

My vacuum advance canister seems to be correct, but my centrifugal advance only gives me about 23 at 2000rpm (with 10 of base timing)
So, with the factory recommended 5 of base timing the centrifugal would only add about 18 of crank degree instead of about 25.

I have attached pictures of my centrifugal advance. The weights are labeled 130, the center plate 370 and the base plate 128

Can anyone help?
« Last Edit: June 21, 2017, 02:19:36 PM by DeVille68 »
1968 Cadillac DeVille Convertible (silver pine green)