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72 Eldorado

Started by firedan, February 12, 2017, 06:41:57 AM

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firedan

I have a 72 Eldorado with just 60k on it and cant figure out the heat is on constantly. The temp dial works and the heat valve seems to work when I hook vac to it but don't get vacuum from the heater box. Any ideals would be great

Scot Minesinger

You should have a shop manual and Cadillac Tim's book (Google Cadillac Tim in Iva, SC and call) to fix your climate control or simply get heat to turn off.  For heat to be on regardless of vacuum signal to valve, the valve must be stuck open or not seal well.  This valve closes with a high vacuum signal I believe (or it is the other way around), in any event vacuum on or off valve you should experience a change.  Reads like valve is bad - inexpensive and easy to change.  The internal air flow can be directed over a/c coil, heater core, or combo as controlled by the programmer.  You may have issues with your programmer or something else behind glove box.  Start reading he manuals and it should put you on a path to fix the car.  If vacuum lines are original or in question replace them - one at a time.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

"Cadillac Kid" Greg Surfas 15364

Dan,
First of all, the water control valve (what you are refering to as the heat valve) is a normally open valve meaning that there will be water flow through the valve with no vacuum signal to the valve.  The valve is only closed (by a vacuum signal) when the system is in the Max-cooling mode. 

That said, there are two distinct possibilities that stand out and I would check them in this order.  A disconnect in the sensor string will drive the system to full heat.  Frequently when the dash top is removed or work goes on behind the dash the in-car sensor is disconnected or broken.  A factory service manual (FSM) will give you all the wiring diagrams so you can check the connections using it.  I have had about a 80% success rate in cases like this by simply disconnecting the sensors, cleaning and tightening up the electrical connections and re connecting them.

You say the temperature control "dial" works, so with the assumption you mean moving the dial from full heat to full cooling results in a change of fan speed and a change in outlets functioning.  If that is the case I would look to the shaft coming out of the top of the programmer/controller.  That is the black plastic device on the passenger side of the interior and is located behind the glove box.  The shaft is connected via "bell crank" to the temperature control door.  This connection often loosens up or is inadvertently installed in correctly, with the temperature control door locked in the full heat position.

The FSM gives you full information on resetting this control to the correct position.

Again those are the things I would check first.

Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

"Cadillac Kid" Greg Surfas 15364

PS,
The FSM provides a full explanation of the system, its components, how they function and their diagnosis.  The big issue with the FSM is their use of an electrical control simulator in diagnosis.  If you fully understand the rest of what the Manual describes this tool is unnecessary for an accurate diagnosis.  I have NEVER had to use mine for a diagnosis.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Jeff Rosansky CLC #28373

Not sure how similar the 72 is to a 70, but on the 70 the valve is closed until vac opens it. You can tell if water is flowing/not by taking the rad cap off (cold of course). The heater hose dumps water back to the radiator just under the cap so you can see if it is on/not without having to feel around a hot engine. You can also take a piece of vac line and hook it to the valve and suck. This will either open/close it. You can see if It works That way and go from there. I don't know how much vac it takes to activate the valve however.
Jeff
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

"Cadillac Kid" Greg Surfas 15364

changed in 71 Jeff
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Scot Minesinger

Jeff,

Big changes in climate control from 70 to 71, no more power servo in 71, and a programmer was used interior mounted behind glove box.  The 1971 is much easier to work on than the 1970 cc.  For me, the most difficult climate control to work on aside from 1964 is 1969/70 due to temp wheel dash mtd unit removal/install and heater core replacement.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Jeff Rosansky CLC #28373

#7
Welllll then dont I feel like an idiot............... nevermind!!
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

"Cadillac Kid" Greg Surfas 15364

Jeff,
In the early years (1950-76) development of Automotive AC closely followed that of commercial AC.  The changes in knowledge, based upon recent experience and the technological development of components and control system strategy was in a continuous state of flux.  For that reason, an in- depth understanding of the basics of Refrigeration and electrical controls is necessary, but trying to remember all the details of components and system functions is a task best left to the FSM.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

firedan

thank you guys so much I now have few more areas to look and get me a manual. where is the sensor, I did see on the dash on pass side a large hose hooked to something I don't know what is

The Tassie Devil(le)

There is a small perforated area above and to the left of the glove box.   It is under there.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

firedan

yup that's it is that the sensor thank you if so

kkkaiser

not trying to hijack thread, but to the earlier reply about a perforated area above glove box,,,   i have a 73,, with some heater and ac issues,,, heater works,, just doesn't change temp,, i can only change fan speed or rate of blow.

would this little perforated area be visible on the dash of the 73 elude....???  i dont see anything like that visible on the dash or is it under the dash behind the glove box??

Gene Beaird

Been a while, but I think the sensor on our 79 Seville was under the center of the dash pad.  You had to pull the dash pad (not a big deal here) to get to it. 

If the sensor is disconnected or is faulty, the system will default to heat/defrost, no matter what the switches on the dash say.  These sensors are usually pretty trouble-free, so I'd look for it to be disconnected (especially if anyone has been in the dash, say to install an aftermarket radio). 

The climate control unit under the dash also has to have it's own vacuum source.  The one for our Seville went into the firewall just to the left (inboard) of the evaporator housing.  If that vacuum hose is disconnected, split, misrouted, the system will default to heat/defrost, no matter what the switches on the dash say. 

Gene Beaird,
1968 Calais
1979 Seville
Pearland, Texas
CLC Member No. 29873

"Cadillac Kid" Greg Surfas 15364

The 71-73 ALL use the same dash top.  To find the sensor, look under the dash on the passenger side above the glove box for a hose that runs from the underside of the dash top (where it connects to the sensor) to the programmer/control unit.

Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

The Tassie Devil(le)

Sorry, but the '71 dash top is different to the '72.

The sensor is in a different place in the '71.   The '71 has a non-perforated top.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

firedan

no worries all good, but i give up I ordered a FSM so I can figure out. I messed with today and I not so sure the climate control is working or is dirty. Seems if I move the dial a few times the fan changes speed, and still no vacuum to the heater control valve.

m-mman

As an FYI when the power fuse for the system opens, the entire system defaults to full heat . . .
ALL THE ABOVE SUGGESTIONS APPLY . .  also do a quick check on your fuses.
1929 341B Town Sedan
1971 Miller-Meteor Lifeliner ambulance
Other non-Cadillac cars
Near Los Angeles, California

CLC #29634

DanishEldoradoFan

My 72 eldo had the same problem. Using the Shop manual, and time .. a LOT of time, i finally discovered, that the arm that turns the port for open and closing the hot air, was loose. The arm moved (by vacuum), but the door didn't follow :o) Simple fault, but very time-consuming to figure out!
Niels, Denmark

firedan

thanks for all the help guys, I'm still not having vac where suppose  to be but I think,  will have to wait on manual to hopefully fix the problem