I have another thread out there regarding the Siemens VDO blower: http://www.chevelles.com/forums/showthread.php?t=226353 and have a problem which may or may not be related.

I installed a new M&H A/C harness days before the blower install. Cut the old purple/power & black/ground wires to the blower motor and left the 2 new ones there for the shop to connect to the new blower. (It took them some 2-3 hours to get the Siemens installed BTW.) Told shop to transfer ground spade from old blower and reattach with a star washer. Also grounded A/C relay to firewall using new star washer.

So I get the car back, turn on the key and no blower speeds. I think I heard a muffled winding down of the 'new' blower, then nothing. No smoke or electrical smells either. I thought wait a minute, that can't be right since the 30A inline power fuse is not installed. Sure enough, it was missing. Once installed, still nothing. BTW: I did install a new horn relay (the horns work) as well as a new M&H horn-to-A/C relay wire, so it is all new material.

The power to the horn is good, new wire, new fuse, but I don't hear the relay clicking at any of the fan speeds. Should it be clicking? Can I quickly test the relay on the car with a digital multi-tester? The blower did work prior to these updates (is that the right word?). I wanted to change the blower due to squeaking at low speeds.

Other thing I notice is in the fuse block. In the upper right-hand corner is a blown 25A fuse called A/C TCS. Is this part of the equation here? I have removed my TCS relay and cut/capped the Dark Blue & Black w/ Pink Tracer wires in the engine harness that lead to the starter solenoid, so no wires grounding-out. The green TCS wire to the temp sender unit is completely removed. Tranny TCS is still there with wiring that leads to, I believe, the Dark Blue wire I cut, so I don't see an active circuit.

1.) So why is this A/C TCS fuse popping in the first place?

2.) Is this fuse even related to the blower motor function?

Trying to give out as much detail as possible before I fall asleep :boring:

Try jumping out the purple wire from the blower relay to +12v to see if you get anything/ There is a wire in the dash...brown I believe that if not connected you won't have anything. It is near the hvac controls .

I bought a 25A circuit breaker for the A/C TCS circuit. Does the power flow through the fuseblock from the center, outward (it matters with a C.B.)?

Looking over some wiring diagrams, I found a possible mix-up regarding the Compressor Switch wiring. Page 515 of the assembly manual shows the C.S. wired with the Lt Green on left terminal, Tan & Gray on the right terminal. Yet the harness is wrapped such that it curves to the connector to fit just the opposite. Can someone verify which way is correct?

Yes, Bowtie70ss, the Brown power wire is connected and with the exception of the above Q, all connectors are secured.

I've been through this all day trying to understand the circuits. Until I can stop that 25A from blowing, I am stuck. I'll bet that POS blower motor took a crap from the get-go.

Other thing I notice is in the fuse block. In the upper right-hand corner is a blown 25A fuse called A/C TCS. Is this part of the equation here?

Yep. That fuse feeds this wire.

http://www.chevelles.com/showroom/data/500/DSC00565.JPG

The black/pink tracer feeds the TCS, the brown connects to the A/C harness. If you are not using TCS anymore, cut the black/pink tracer here. This fuse powers the blower motor in all speeds except high. Disconnect blower motor and see if fuse still blows.

I bought a 25A circuit breaker for the A/C TCS circuit. Does the power flow through the fuseblock from the center, outward (it matters with a C.B.)?

Pretty sure is flows from outside towards the center. Its easy to test, remove fuse, turn key on, check for which side of fuse clip has power.

Okay I got it running, and boy did I learn how the blower circuit works!! Allow me some space here to layout how it all flows - atleast on '70 A/C cars - as I hope this will be helpful to others.

Power Path:

Fuseblock 25A "A/C TCS" exits a Brown wire, ignition power feed and is part of the Dash Harness. It runs to the connector undee70ss shows in his pic at which point it connects into A/C Harness and runs to the HVAC Master Switch.

Master Switch provides direct power to all blower speeds - except HI as mentioned below. The only time the blower is powered OFF is when the HVAC panel switch is fully to the leftside under the word OFF. All other times the fan is blowing atleast at LO speed.

Master Switch ON:1.) Light Green wire feeds power to A/C Compressor Switch. If Compressor Switch is ON, then Tan wire sends power to the Thermal Switch (Dark Green & Tan wires located on the Evaporator Case) which decides when the A/C Compressor clutch kicks in. Also if Comp Switch is on, Gray wire powers FSS. You will notice that the Fan Speed Switch actually has 2 LO speeds (not an OFF as the service manual states) Maybe someone can better explain the need for the Gray Compressor power wire to the FSS as it seems redundant...
2.) Master also sends power to the Fan Speed Switch (FSS) on HVAC panel via another Tan wire independent of Compressor Switch position.

Compressor Switch OFF & Master Switch ON:

These are Vent & Heater blower speeds. From the Master Switch, power runs thru a Tan wire to the FSS. Outputs to the blower resistor include:
Yellow = LO 16G wire
Light Green = Medium 1 16G wire
Light Blue - Medium 2 14G wire

Dark Blue = HI 18G wire avoids the Resistor assembly. It is only a signal wire to the A/C evaporator relay. This relay is for any high-speed blower need and gets its power directly from the horn relay bus via a 10g fused wire. I think there is a lot of confusion about this relay. This SPST relay will "click" when the HI speed FSS is selected and is wired as such:

Power In: Black 10G to AGC 30A fuse to short Orange 12G
Power Out: Purple 12G
Signal: 18G Dark Blue
Ground: 16G Black

Back to the output fron the Resistor Assembly. Output is via a Dark Blue 12G wire which splices with the relay 12G High-speed Purple wire within the harness loom. After the splice, purple 12G runs to the blower motor.