IrishJoker

I am having an issue with the High Speed Blower Switch:

I can tell no difference between position 3 and position 4 of the Fan switch. Therefore I believe I have a high speed blower issue.

According to information on page 1B-20 of the Shop Manual there are two fuses for the air conditioning system: 1 fuse in the fuse block and 1 fuse protecting the high speed blower circuit.

This fuse is supposed to be located in the electrical wiring between the "Junction terminal" and the Air Conditioning relay.
Additionally there is a RELAY and a Blower Resistor involved.

By the way, I do not see this 2nd fuse in the wiring diagram, which is "Fig 1B-3-C60" on page 1B-3.

My questions are as follows:

1. Where is the Relay located?

2. Where is the fuse located?

3. Where is the Resistor located?

I am making an assumption that since the A/C works and the Fan/Blower switch works in the lower 3 positions, something has happened in any of the 3 components listed above.

The Shop Manual talks about replacing all 3 of these components but does not provide a picture diagram of where they are located. See pages 1B-20 and 1B-21.

I would appreciate any help anyone can provide.

IrishJoker

Come on - somebody has to know the location of these parts??????

chevymans 77

The blower resister should be mounted on top of the evaporator coil box, the resisters will be sticking down into the coil box. The blower relay is mounted on the firewall right near the resisters. It is not uncommon for the high-speed relay to fail. The relay puts 12 volts directly to the blower for high speed bypassing the resister. The wires for the high speed relay and the resisters exit the wiring harness in the same opening. They are a couple inches apart. This is how it is on my 77 but I don't think GM changed much from 77 to 81 as for as the placement of the components.

Neal

antongonza

I had same problem with my 78 corvette no high speed only low and medium speed, found problem was blower high speed relay was not grounding. I grounded neg. side of relay to engine and works fine.
Hope this helps .

SIXFOOTER

OK, here is the schematic for the 81 blower.
As you can see there is only 1 fuse, 25A. If the blower blows at all the fuse is good. The relay is located on the firewall, passenger side above the blower, silver in color with a connector on the botton. The resistors are located inside the AC plenum, mounted from the top right next to the relay, it has a 4 wire connector on top.
get out the voltmeter, check for voltage on the dark blue wire on the resistor pack, it should change with the 1, 2 and 3 positions of the fan switch. 4 on the switch should turn on the relay and bypass the resistors and put a full 12v on the fan via the Red wire on the relay.

IrishJoker

Thank you - again you came through - I think when the shop manual talked about the 2nd fuse they were referring to the "Fusible Link" as shown on the diagram coming into the High Speed Blower Relay.
Is this just a standard 12V relay that I can pick up at an Auto Parts Store. Being ignorant here - I have never had to replace a car relay other then something along the lines of a flasher before.

Paul L

Some years do have a separate in-line fuse for #4 blower speed. Here is one on my 1974. The original was corroded and I used a generic replacement.