69 Eldo Blower on all the time?

[brian rachlin]

I have owned many Cadillac convertibles over the years, and currently have a 76 Eldo convert, and an 85 Eldo convert.  I just got a 69 Eldo, obviously not a convertible, but has a beautiful original black cloth and vinyl interior.  I suspect the car was originally white, the car is black with gold two-tone treatment on the raised hood and trunk areas, with a nice pinstripe.  

1 problem with it is the blower stays on all the time. I am not talking about the low setting for constant venting that some Cadillacs had, I am talking about medium fan speed, all the time, with no change from off to auto.  The compressor does engage and it blows cold air, but everything comes through the defrost outlets, it does not transfer to the dash vents or the floor vent at the appropriate settings for that to occur.

Where do I start trying to troubleshoot this?

Thanks,

Brian

[denise 20352]

  My first suspicion would be that the Climatron malfunctioned and someone just hard-wired some power to the resistor block to make the fan do something, but that may not be right.

  If you turn the temp control from cold to hot, with the engine warmed up, is there any change in the temperature of the air coming out of the vents?  Thats the electrical part of the circuit...the programmer has a little motor in it that moves a valve to mix hot air and cold.

  I guess I would start with checking to see if there is any vacuum to the control head, and power.  With the engine running, you can pull the connector off, and at least one of those hoses should have vacuum going to it.  There should also be 12v to at least one of the big wires that goes into the connector.  Take a good look at the connector while youre there, because those things overheat and get burnt.

   The only manual that I have is from a 76, and I dont have it in front of me right now, but there is a start, at least.

-denise

[brian rachlin]

Temp control is working, air changes from cold to hot correctly, but unit does not go off, and doesnt change modes from floor to dash to defog, stays on defog all the time.

Thanks,

Brian

[denise 20352]

    If it hasnt changed to 1976, the defrost door is activated directly by the vacuum switch in the control head, so I would look for a lack of vacuum to the system, to begin with.  The vacuum line might go in on the drivers side firewall, and sometimes people will mess around with the vacuum lines and not hook it up.  If you have cruise control or vacuum parking brake release, it is probably teed into the same line.  Somewhere under the dash, it has to connect vacuum to that connector on the control head, and in any mode other than defrost, the vacuum should close that defrost door, allowing the air to go to floor or panel vents.  It is up to the programmer to open and close those motors, but it sounds like you have no vacuum to the system at all.  The fan might actually be a separate problem, but I would start with getting the ducts working.

-denise

[brian rachlin]

Its supposed to be a decent day, weather wise in my area, and I will do some checking on this.  Thanks for the advice, Denise, this is exactly how a well run message board should operate.

Have a happy and healthy New Year!

Brian

[Joel Den Haan #21586]

Its supposed to be a decent day, weather wise in my area, and I will do some checking on this.  Thanks for the advice, Denise, this is exactly how a well run message board should operate.

Have a happy and healthy New Year!

Brian

Hi Brian-
While youre at it, Ive been looking at my shop manual troubleshooting section, along with my Haynes troubleshooting, and you might want to look at the blower resistor relay assembly.  An open circuit in the resistor will limit both available fan speeds and by extension the function of the programmer to move air around the vent system.  At least thats what I found when I ran into the same problem on my 78SDV.  

Joel Den Haan #21586

[bill henry]

check the power servo under the hood could be stuck . get a gm shop manual the are great for the climate systems

[bill henry]

also ththe 69 system is completely different tha a 78 but is the same as a 70 i think

[TJ H 20664]

I was talking to a friend of mine that has a 69 about my 78 blower problems and he said the the 69 has relays to control the blower speeds just like the 78 does. If the relays are the same as in the 78 the design seems prone to overheating.  The problem one in my 78 had warped to the point where it didnt make contact anymore.  I would imagine that it could do the oppsite thing and warp shut.   If you dont have a book that Ids the relays just start pulling them out 1 by 1 and see if one shuts off the blower, if it does swap it with an identical one and see if it then works better.   On my 78 someone had run a wire under the dash out the door and under the hood to the resistor block to make the fan run all the time.   If the 69 is like the 73 the resistor block is on the control head and the relays switch the differnt resistors in and out for differnt speeds on the 78 the relays are by the fuse block. I have no idea where they are on the 69 I would assume near the fuses since the control head is not far from there also.

TJ H
20664
StPaul/Mpls MN USA
73 Eldo convert(s)
78 CDV

[bill henry]

yes the 69 has a relay  but all a relay is is an eletricaly controled switch . i had a 78 prior to the 70 i have now and put the relay update in it. that being said the different fan speeds come from a multi contact switch to the resistors in the ac box on a 78 the rotory switch in the dash head does this in a 69 or 70 the power servo does this

[denise 20352]

> The problem one in my 78 had warped to the point where it didnt make contact anymore.

    The relay in my 78 loosened up internally and shorted out, caused the wires going to the control head to get really hot, caused the alternator light to stay on even when the key was off, and then melted the A/C fuse into a puddle of goo.  I ended up actually amputating the half of the fusebox that had the buzzer and that relay on it, and converting to a more modern type of relay.

    Some of the purists will scream, Oh no, you modified a Cadillac! but guess what...there were at least three different styles of fuseboxes for that vintage, and I would challenge anyone (except Yann) to tell me which one belongs in your car.  Besides, why replace a failed part with the same thing when it  failed because of a blatantly obvious design flaw?  If you take the top off of one and look inside it, youll see it immediately.

-denise

[denise 20352]

  Does it use vacuum?

[bill henry]

yes the power servo uses vacuum to move to its different positions it is under the hood sort of on top the firewall many hoes and electrical contacts on it

[denise]

   There might not be vacuum to that valve, then.  That is where I would start.