1970s 78 Eldo- In-Car Temp Sensor

[Jakes]

This is in the category of "what were they thinking?". The HVAC system is controlled by three temp sensors: "ambient sensor" attached to the top of the evaporator enclosure forward of the firewall, "in-car sensor" attached to the back of the upper dash to the left of the Cadillac script (photo below), and the temp control potentiometer behind the lower dash controlled by the temp dial.

The heater core was leaking and needed to be replaced which requires removal of the two-part dashboard.  One of the club's esteemed members, Joe Caristo, is an expert at doing the job and came up from nearby PA to Long Island.  I helped Joe reinstall the dashboard after the heater core was replaced.  After it was done the system was blowing warm air at any setting.  Long story short...I later discovered that, in helping Joe, I had accidentally reattached the elec. connector to the in-car sensor behind the upper dash off-center, i.e., the left part of the connector was plugged into the right tab of the sensor (photo below).   Try as I might, there was simply no room to correct the mistake from under the dash even with the glove box removed.  Joe came back later to remove the upper dash, reconnected the in-car sensor properly and ...voila...problem solved.

Now...why in heaven's name didn't GM, in its infinite wisdom, design a simple, small panel with two decorative screws that would house the in-car sensor and allow for access from the front of the dash?  Instead, to replace this simple component, the upper das must be removed...a time-consuming task.  The ambient sensor under the hood is easily removable in about a minute and the temp. potentiometer is accessible by removing the panel under the steering column.  I guess the geniuses at GM thought that the in-car sensor would never go bad....famous last words!

[TJ Hopland]

How many of those went bad in their testing or even in the first 10 years?  Probably almost none. Anyone around in the service game when these were fairly new?   I assume they were fairly reliable based on how reliable they are at this age which is way longer than anyone expected them to last.  Maybe not as reliable as a cable operated system but had to be similar to the more typical vac manual systems. 

Look how difficult they made it to change many of the light bulbs which were basically for sure going to fail at some point in the cars expected average lifetime.  Oil filters and radiator drains above things so you can't get a straight shot to your drain pan?

[bcroe]

Cars were made for the least initial cost in parts
and assembly labor.  Difficulty in servicing along
with replacement parts, was not a consideration. 
If anything more difficult is to their advantage,
by increasing the chance of you buying a new car. 
Bruce (77 daily driver) Roe