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1976 Cadillac Deville AC, Heater Switch

Started by EAM 17806, August 02, 2022, 10:09:24 AM

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EAM 17806

My blower fan motor goes on low mode but not on HIGH when switched to high AC or Heat;  fan motor tested in good shape; what's going on and what can be wrong?  EAM
Ev Marabian

1976 Cadillac Coupe DeVille, 1989 Chevrolet Caprice Classic, 1990 Pontiac Bonneville and 1996 Buick Skylark

bcroe

#1
If it does not blow on DEFROST, I expect to find heat
damaged wiring in the dash manual control unit.  If it
fails in auto Climate Control mode, I would expect to
find a fault in the programmer unit behind the dash. 
Get a wiring diagram.  good luck, Bruce Roe

Dave Shepherd

Or, the high blower relay is bad, memory has faded some. Lol

cadillactim

Does blower run on Auto or Defrost? If it runs in Defrost but not Auto, thermal switches to enable blower may be bad. If not working on Defrost check relay.

Tim
Tim Groves

EAM 17806

Quote from: cadillactim on August 02, 2022, 06:40:47 PMDoes blower run on Auto or Defrost? If it runs in Defrost but not Auto, thermal switches to enable blower may be bad. If not working on Defrost check relay.

Tim
Hi TIM:  The blower runs on low only in all situations. Where else can I look for a remedy?  EAM
Ev Marabian

1976 Cadillac Coupe DeVille, 1989 Chevrolet Caprice Classic, 1990 Pontiac Bonneville and 1996 Buick Skylark

"Cadillac Kid" Greg Surfas 15364

Ev
Check the connection at the blower relay and the relay itself
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-

Dave Shepherd

That 3 of us that suggested the relay as the issue.

EAM 17806

#7
Quote from: Dave Shepherd on August 03, 2022, 03:57:57 PMThat 3 of us that suggested the relay as the issue.
Two top brand relays have been installed, AC Delco and Standard, still no good.  EAM
Ev Marabian

1976 Cadillac Coupe DeVille, 1989 Chevrolet Caprice Classic, 1990 Pontiac Bonneville and 1996 Buick Skylark

Dave Shepherd

#8
Have you checked to see if the relay is powered/functioning  on demand?

bcroe

It might be a component.  But I have seen countless
cases where wiring in high current circuits like
rear defog or blower, burns out.  The contacts do not
use long life noble metals.  With current they heat,
heat causes oxidation, more resistance, more heat,
more oxidation...     good luck, Bruce Roe

cadillactim

On OFF and LO the fan circuit is from the dash control to the brown wire in the programmer. Current must flow through all resistors which gives low speed. Relay is not energized.

But in all other settings low speed circuit is not used at all, as relay is energized and current goes into programmer through Orange/black wire. Fan speed is then controlled by vacuum motor position allowing low, medium, and high speeds.

In AUTO HI and DEFROST, current also goes directly to fan, which bypasses resistors in programmer.

Therefore, if you have only low fan in all settings issue seems to be that programmer is stuck in low speed position. If it is stuck then you will not be able to control the temperature from cold to hot.

Can you control the temperature with the temperature wheel on the dash control?

Tim
Tim Groves

EAM 17806

Quote from: cadillactim on August 07, 2022, 11:41:09 PMOn OFF and LO the fan circuit is from the dash control to the brown wire in the programmer. Current must flow through all resistors which gives low speed. Relay is not energized.

But in all other settings low speed circuit is not used at all, as relay is energized and current goes into programmer through Orange/black wire. Fan speed is then controlled by vacuum motor position allowing low, medium, and high speeds.

In AUTO HI and DEFROST, current also goes directly to fan, which bypasses resistors in programmer.

Therefore, if you have only low fan in all settings issue seems to be that programmer is stuck in low speed position. If it is stuck then you will not be able to control the temperature from cold to hot.

Can you control the temperature with the temperature wheel on the dash control?

THANKS for the info TIM!  I just hope I'm not going to need a Climate Conrol switch.  EAM
Ev Marabian

1976 Cadillac Coupe DeVille, 1989 Chevrolet Caprice Classic, 1990 Pontiac Bonneville and 1996 Buick Skylark