1970s 1979 Eldorado Heater / AC issue

[NatoNYC]

Hi - the fan in my 1979 Eldorado Heater / AC unit stopped blowing air yesterday.  My mechanic tested the blower and it works (with direct power).  The fuse was blown and when he replaced it, it immediately blew again, so he believes there is a short somewhere, but doesn't know where.  He's also unsure where the relay might be located. Has anyone else experienced this, and if so can you provide any guidance please?  Thanks.   

[TJ Hopland]

I don't have a 79 manual or recent(ish) hands on experience on one so only guessing and this would be an oddball setup being a 'new' body style but still having the 'old' climate control setup. 80 they got the 'digital' setup which you would assume was intended to go in the new 79's but wasn't ready yet so they had to just hack the old system in.

78 C cars had a relay panel above your left foot and there was a blower relay in there that often had overheating issues in the relay itself and the socket.  That didn't in itself result in a blown fuse but many of the workarounds could have. 

The fan speed on these happens in the programmer which is an assembly with a lot going on in it over more on the passenger side.  Its got some control doors in it. Its got the amplifier in it for the control signal.  Its also got the wiper switch and resistors that steps through the fan speeds.  As far as I know those were pretty reliable as far as the blower speed part but who knows maybe they did some cost cutting or fitting in a smaller car mods for the end of the run before going to electronic.

What fries all the blower stuff is either the original blowers getting worn or dry on lube and dragging thus drawing more power and overloading things or replacement blowers not quite being up to the original spec in one way or another and also drawing more power and then eventually having the same lube and wear issues so still killing things.  As time went on they just didn't build any headroom into the blower circuits. 

If no one else can help I can look at the 80 manual I have but the old system would be for the C cars since the E's had the digital by then so my diagrams may not be correct for your car.

[NatoNYC]

Thanks so much for responding, truly appreciated.  I do have the manuals for the 79 Eldorado; my mechanic is mostly looking for a "next step" place to start, so I'll let him know your thoughts.