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Rattle in 70's climate control

Started by TJ Hopland, March 19, 2009, 01:11:49 AM

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TJ Hopland

Now that its getting warmer I have noticed a sort of rattle sound coming from the dash in my 75 eldo.  It is related to the temp setting.  Its louder and faster the cooler the dial is set.  Example dial set at 70, interior temp 72, I will notice the sound.  If I set the dial to 60 it gets louder and faster.  If I set the dial to 75 I hardly notice it.  If I set it to 85 or all winter long when the interior temp did not likely get above 70 I did not notice it.   On this 75 Eldo this happens no matter where the lever is set, off, econ, auto.  I think my 73 eldo does the same thing but only on auto.  It does not do it on vent or off. It does require the engine to be running so it must be related to something that needs vacuum to operate.   I can't imagine this was a normal noise so something must be worn or need some lube?   Its not the A/C compressor because my 73 has not had one since I owned it and the 75 I unplugged the clutch wire because it did not sound very healthy when it ran.   The 75 is a winter car and the 73 is a summer convertible so its not really been a high priority to figure out but the engine in my 73 is still out of comission so I may be driving the 75 a few more months and its really starting to big me.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

homeonprunehill

03-18-09
TJ, how's the radio working ? When I was yougner and a rattle developed, we being, young and  nieve would just"turn-up" the radio to mask  the rattle untill we couled figule out what was rattrleing. HTH,Jim
USED,ABUSED AND MISUSED CADILLACS AND LA SALLES

Ted in Olympia WA

Selling used Eldorado Parts from 1971-1978.  Member Number 25659.

TJ Hopland

Its not related to the fan speed.  The sound will change as I operate the temp dial even with the control set to off which leaves the fan on the low speed.

Its the original radio so it has trouble getting loud enough to cover up all the little noises and still sound good.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

35-709

My '71 SDV made the same sort of noise, a rapid clicking sound, not fan related.  Unfortunately I sold the car before I figured it out.
1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold - but still in the family
1950 Jaguar Mark V Saloon resto-mod - Sold
1942 Cadillac 6269 - Sold
1968 Pontiac Bonneville Convertible - Sold
1950 Packard 2dr. Club Sedan
1935 Glenn Pray - Auburn Boattail Speedster, Gen. 2

Tod- NTCLC

Foam around one of the vent doors has dried to dust.  As you adjust the temp, more vac. is directed to that door, and the '"slamming" of the door increases in speed.  Ease off the temp until the air is no longer directed to the dash vents, and the programmer will call for the door to be in the open/relaxed position, directing air to floor vents and the noise will stop.

Test it - disconnect the vac supply under the hood that runs into the Climate control - noise stops?  Then it is related to the door operation.

Just a guess, but seems plausible based on your troubleshooting of the other variables.

Finding the door, and restoring the seal/operation might be a major job.  If it isn't high priority, put a cut-off valve in the heater line for the summer, and leave the Temp dial at a higher setting until you can fix it - air will come out of floor vents, but won't be heated.  Or, just leave the vac. supply disconnected (you would still need a manual cut-off valve since the vacuum is what operates the the climate control hot water supply valve).

"Cadillac Kid" Greg Surfas 15364

TJ,
What this sounds like is either loose linkage or the rivets have loosened in your air temperature "door". This is the damper or rather diverter that directs air over the heater core as required to bring it up to the desired temp.  As the door diverts away from the heater (when you dial up a cooler temperature) more force is everted on it and something is loose.
First of all check the clamp that holds this damper's linkage to the programmer output shaft.  It is the one extending vertically upwards from the programmer. You can become a contortionist, or if you want to do it the easy way, pull your glove box liner out and it will be right there. I hope that is where you find the problem, because getting into the heater box for the actual dampers is flat rate book listed as an 11 hour job.
I've replaced four heater cores on '70s era cars and if all you have is a rattle. I will second the suggestion to turn the radio up,
Greg
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-

Dan Marinola

Hi Guys, I too have this problem with my 78 Eldorado. It seems to be a ticking noise that varies with the temp setting,and is definitly coming from the programmer assembley behind the glove box. Tick, Tick Tick. It drives me crazy! I can't believe there isn't a fix for this that is common amoungst fellow members. Any help out there?
Daniel P. Marinola

TJ Hopland

Glad to hear its not just my cars that have this problem.  I have had one of the 73's for 15 years and I think its always done it and it does not seem to be any worse.  At least that one does not do it on vent or off plus its a convert and 90% of the time I am running top down.

Luckily the 75 came with the glove box and liner in the trunk and I have been too lazy to put it back in.  Should make it easier to get a look at the area in question.   I do have service manuals for 73-75-77-78.

It sounds more like a relay sort of thing but I suppose the air door thing could be.  If it was the lack of foam on the doors why would it still do it when its in a mid position or are the doors open or closed?
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

35-709

Mine definitely sounded like a relay.
1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold - but still in the family
1950 Jaguar Mark V Saloon resto-mod - Sold
1942 Cadillac 6269 - Sold
1968 Pontiac Bonneville Convertible - Sold
1950 Packard 2dr. Club Sedan
1935 Glenn Pray - Auburn Boattail Speedster, Gen. 2

"Cadillac Kid" Greg Surfas 15364

Geoff,
Leak in the vacuum lines or faulty vacuum checking valve in the programmer.  Causes the programmer to hunt back and forth rapidly.  The clicking you hear is the linkage moving back and forth.
Greg
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-

35-709

Thank you Greg.  The car went to Germany, hope he can get it working properly.  Never heard the first word from him after he bought the car, although I emailed him.
Geoff
1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold - but still in the family
1950 Jaguar Mark V Saloon resto-mod - Sold
1942 Cadillac 6269 - Sold
1968 Pontiac Bonneville Convertible - Sold
1950 Packard 2dr. Club Sedan
1935 Glenn Pray - Auburn Boattail Speedster, Gen. 2

TJ Hopland

Check valve?   I cant remember is there a vacuum reserve tank for the heating?  Any idea where that valve is located?  I have service manuals around somewhere, may be time to dig them out.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

"Cadillac Kid" Greg Surfas 15364

Its called the vacuum checking valve and it is located within the cover of the programmer of all '70s era cars.
Greg
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-

TJ Hopland

Would putting a check valve in the supply line help if thats the problem?
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

"Cadillac Kid" Greg Surfas 15364

TJ,
The vacuum checking valve in the programmer is a specialized, three port check valve whos function is to control the loss of the variable vacuum signal (from the transducer) when engine vacuum changes during normal driving.  Consider it an attempt at "freeze framing" the vacuum circuit. When they go out it can result in a back and forth oscillation of the programmer actuator.  More typically, one of the vacuum lines to and from this device either get disconnected or broken.
Greg
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-