Intermittent cabin fan

The cabin fan (AC blower) in my 512TR will intermittently not work. If I jiggle the wires on the driver's side of the circuit board, it comes back on. I need to track this down and correct the loose connection. Before I make myself crazy with the Italian wiring schematics, does anyone have insight as to the connector (or better yet, wire) that is the likely culprit?

 

Which connector ran the AC cabin fan?
Right now the car stalled while charging the ac system and won't start (no fuel, no spark). The engine turns over briskly and the dash lights are on but also no cabin ac fan. I have the Dave Helms conversion (which has performed brilliantly for over 30K miles) which uses a modified battery connection. I will investigate more today. What fun.
Now that you mention it, I think there is a fuse in that circuit that I have not checked yet. Hmmm.
Dennis, you may be on to something.

 

The passenger side of the pair of what?

 

Wow, that is a work of art. I have a few questions:
#11 - thermoswitch on radiator for cooling fans - where is this in the car? There is nothing on the condensor that I recall.
#118 - engine oil radiator fans - this is not valid on USA cars (the wiring harness is there, but no fan)
So, how do the condensor fans know when to turn on? Are they always on when the minimum pressure switch #18 is closed? I assume #82 is the trinary switch located on the receiver/dryer? Besides setting high and low pressure limits, what is the third function of this switch? Is it possibly also the #11 thermoswitch for the cooling fans?

 

If I am reading your magnificent diagram correctly,

12v power comes from battery via red wire to fuse #3 on main board (20A)
then to relay B position 30 (red wire) and out position 87 (green wire) when energized by position 85 (orange wire) from minimal pressure switch.
the green wire exits connector C, position 6 and travels to the mysterious "thermoswitch on radiator" and then to condensor fans.

In my Dave Helms converted fuse box, fuse #3 is moved to position 6 on a separate fuse panel energized by direct battery connection and then travels to relay B which is now also mounted separate from the fuse box. The relay output 87 bypasses the fuse box and connects directly to the green wire, now separated from connector C, which then heads to the fans.

I have not confirmed this yet, but I will attempt to do so and locate the source of the blowing 20A fuse this morning. In the absence of a shorting relay, it looks like front bumper removal is in my immediate future.

Quavion, you are da man!

 

OK, I thought there was a separate thermoswitch for the ac fans but it makes sense that this is tied to the coolant temperature, but if this were true, wouldn't the ac fans come on at the same time as the radiator fans (they don't), or does the ECU somehow monitor the temp and turn on the ac and coolant fans at different temperatures? Does the switch provide a range of temperatures to the ECU which then controls different circuits at different temperature settings?
Where on Quavion's diagram is the main ECU?

 

Let me preface this reply by stating I am the LEAST experienced of all previous posters.
I replaced the condensor fans in 2014 because the 20A fuse kept blowing. See post "512TR AC fan removal photos" 9/2/14). I don't recall seeing any thermoswitch on the condensor or lines (unfortunately I was not I-phone aware at that time and the photos were done with a digital camera and stored in some dark recess on my hard drive).
The 512TR has only one thermoswitch for the engine coolant temp, located on the bottom of the LH (driver's side radiator). This switch closes (completes the circuit) to turn on the coolant radiator fans at 195 degrees. The AC condensor fans come on way before that, so there must be some other input to signal the condensor fans to start.
On the receiver/dryer is a Trinary switch with limits for high and low pressure cut-off and also a third (hence, trinary) function to turn on the ac condensor fans at a pressure of around 240 mm Hg. Makes sense to me that this is the signal for the fans rather than a temperature switch. The temperature of the freon (or equivalent) and the pressure should be related, right?

That's my two cents on that matter.

As far as the 30A fuse blowing, I did some testing. On the Dave Helms conversion, 12v power comes into fuse #6 on the separate little fuse panel and goes to relay #6 mounted to the back of the board, and from there to the fans. Relay #6 should need input from the trinary switch as well as the AC push button controls.
I installed a new 30A glow fuse and started the engine and the AC. The fuse blew within seconds. I changed the relay and put in a new glow fuse. Same thing, but I was able to record an amp draw of 14.3 before it blew. Hmmm. I put in a non-glow fuse and everything worked perfectly and stayed working and now the amps read 13.48. The AC once again blows cold air. WTF? I can hear that both fans are working. It seems that the glow fuses blow earlier than advertised.
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Here's some further mystery. If I turn the ignition switch to run position and turn on the AC, both fans run and draw 11.42 amps, about right for advertised 5.3 amp draw per fan. But with the engine running and the AC on, the draw goes up to 13.48. Why the 2 amp difference? The fans are just drawing air and should not be affected by the AC being on or off, right? Maybe someone can enlighten me
But, bottom line, it all seems to be working and I did not have to remove the bumper (yet).
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Qavion, your diagrams are professional quality. When I print them off, they are way too small to read. How can we get the final draft blown up like the WSM schematics?

 

Well, there you go, that makes sense. Do you have an opinion regarding glow fuses?
As far as I am concerned, this issue is resolved and I'm going driving. Ain't science wonderful?