72 Eldorado AC Blower Motor Issue

[boseephuss]

Howdy everyone,

Almost have my car back, but a few gremlins persist.  It seems the replacement convertible top motors aren't what they once were, as the replacement I have is overheating.  They think the regulators might need a good cleaning, but hopefully that is an easy diagnosis.

They are also working on the AC, which I understood from the previous owner to be a blower motor issue.  They got it replaced and found that the blower motor only works if the AC is not turned on. And when the AC is turned on the blower motor doesn't operate.

I dropped off the shop manual, but wanted to take a shot in the dark that someone has experienced something similar here.  Thanks for the help!

["Cadillac Kid" Greg Surfas 15364]

I would check the blower relays. Sounds like either incorrect connection, the wrong relay, or a bad relay.
Greg Surfas

[boseephuss]

Thanks!  I will relay that information down the line!

[Steve Lomas]

When you say overheating- the motor itself?   Did you/they replace the relay for the motors also? otherwise this could be half burned out by the old motors and still overheating..

Similarly if the blower motor was sucking too much power- it could have burned out other connections/relays   mine kept blowing a fuse (75 eldorado) -  I eventually put the blower on it's own circuit/ switch under the dash. Not a purist solution, but I like to control the blower independently anyway-  e.g. I can turn the AC off and keep the residual cold air blowing

[Dan LeBlanc]

Previous owner had some climate control issues fixed in my 70.  Whoever did the work used a series of relays to shunt the power around the climate control head for the various blower speeds.  It works, and now the climate control head merely acts as a switching network for the various blower speeds.  Less stress on the control head down the line. 

I have no idea how they did it, all I know is they did.

["Cadillac Kid" Greg Surfas 15364]

 Blower speeds are
Achieved through the resistors in the programmer not through the control head.
Control head signals the blower relays which circuit power through the resistors for blower speed
Greg Surfas

[bcroe]

Blower speeds are
Achieved through the resistors in the programmer not through the control head.
Control head signals the blower relays which circuit power through the resistors for blower speed    Greg Surfas 

That is basically it.  But on so many cars the lower resistor current, lower
speeds are controlled directly, but a relay is used to connect the blower
directly to battery on highest.  My 79 Eldo had no such relay, so I
installed one (to prevent burning out the control).  This is described in
a past Self-Starter, not sure how much applies to earlier years.  Sounds
like someone also put in multiple relays for every speed, maybe overkill. 

Get the manual and trace it out.  Burned car wiring is common, relays
are the fix.  Bruce Roe