What is this?

[Woodhook]

I rewired my 77 K10, but the kit I used didn’t have the new wiring for the AC/heat. I used my existing wire, which is what the instructions suggested. My problem is now the blower motor will only work on low speed. It comes on when the ignition is turned on but will not speed up with the switch. I’m using my existing switch, which worked fine before I started working on the restoration. What is this thing on the firewall and does it have anything to do with my problem? The wire on the left of this thing is part of the AC/heating wiring but doesn’t have anything connected on the right side!I don’t want to start changing resistors and relays unless they are bad.
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[nvrenuf]

The 2 stud block on the firewall is basically a power distribution block, it typically doesn't directly have anything to do with the HVAC.

 

[Dryriver1]

Hello Woodhook! I hope all is well with you and your loved ones.

I think @Snoots, @Ricko1966, @idahovette, @SirRobyn0, or one of our many other expert members will be here shortly and give us a real good explanation.

IMHO I think it is just a bus bar connection, but like I mentioned they will be here shortly to the rescue.

 

[Dryriver1]

The 2 stud block on the firewall is basically a power distribution block, it typically doesn't directly have anything to do with the HVAC.

Like I mentioned @Woodhook this is why I love this forum!

@nvrenuf said:
The 2 stud block on the firewall is basically a power distribution block, it typically doesn't directly have anything to do with the HVAC.

Guys are super helpful!!

 

[SirRobyn0]

It's just a power distribution point, nothing more. Has nothing to do with the heater. FYI we just had another thread on this a few weeks ago....

 

[CalSgt]

It's definitely a bus bar for power...

Several of the ones I have see though have a wire with fusible link going from the right side down to the bulkhead (backside of the fuse block) on the firewall.

 

[Woodhook]

Well that makes my blower problem a little easier to fix! Thanks

 

[Radiohead]

Strictly switching and the speed resistor controls the fan. And good ground. Assuming you have power there to begin with.

 

[Woodhook]

when I removed the old wiring, there was a wire from the right side of this block that went inside the cab and connected to a resistor type connector mounted to the steering shaft. From there, 2, three wire bundles were just laying inside the dash not connected to anything. From what I found searching the internet, they seem to be made for the rear AC/heat on a suburban.

 

[Woodhook]

Radiohead, I have power to the blower motor when the ignition is on (low speed only) Is there any other power source I need?

 

[Snoots]

Actually, one fused wire from that block goes to the input side of the HVAC fan relay.

 

[mtbadbob]

Radiohead, I have power to the blower motor when the ignition is on (low speed only) Is there any other power source I need?

You can run a jumper wire from the 12v supply(red)from the relay to the blower motor. If you get high speed on your blower then, it's probably the relay. Also inspect your resister to make sure none of the coils are burned in two.

 

[Radiohead]

Radiohead, I have power to the blower motor when the ignition is on (low speed only) Is there any other power source I need?

I don't think so. If one speed has power, the resistor seems to be getting juice. Whether it is distributing through the various values to give the speeds seems the problem. But no high speed seems its own problem.

 

[Woodhook]

Thanks gentlemen! I’ll check all your suggestions and let you know what I find!

 

[bolidoendiablado]

I don't think so. If one speed has power, the resistor seems to be getting juice. Whether it is distributing through the various values to give the speeds seems the problem. But no high speed seems its own problem.

Actually, that block provides juice for the high speed position for the blower fan. I’d suggest you also look at the wiring schematics to assist you in the wiring and also understanding it. There’s a red/orange wire that goes to the relay that is attached to the AC box