My Relay Board Seems Naked, Heater Fan Not Running Options

[Trav012000]

I figured the word naked would get some more hits. (IMG:style_emoticons/default/bootyshake.gif)

Anyway, I've got a link here to a picture of my relay board. Now I've been racking my brain for the past week or so trying to track down the problem that's causing my heater fan not to work (as its going to get cold here in the next week or so). Now if I'm reading diagrams correctly, then my relay board is missing a relay for the heater fan. Take a look and let me know if I'm right. I don't need the relay for the rear window defogger, but how about the other relays, should my car not be running?

I've got a 76 that the previous owner converted to dual webbers. Other parts that are kind of important that currently don't work are horn and fresh air blower. Am I lucky enough to just be missing the relay for all three? (IMG:style_emoticons/default/biggrin.gif) (I've not actively sought to fix them just yet)

http://fultonglass.com/relay.JPG

Thanks for the help.

[bperry]

Below is a photo of a relay board with some markings to help out in the discussion.
I'll reference the picture below.



Ok, so you can see what each relay is used for.

First notice the pink and green circles on the heater fan relay socket.
Notice the cyan circle on the T14 connector at the top.
Then also notice the orange circle on the T12 connector lower right.

The heater fan (and the fuel pump in stock configuration) is powered
by the red fuse in the photo above.

This fuse is hot all the time even when the ignitiion is off.
This fuse is directly connected to pin 30 of the heater fan relay which is
the pink circle.
Pin 9 on T14 (cyan circle) is connected to a green/white wire that goes
to a switch that grounds when the heater lever is pulled.
When the heater relay engages, it connects pin 30 (pink circle) to pin 87 (green circle)
Pin 87 (green circle) is connected directly to pin 11 on T12 (orange circle).
Pin 11 on T12 is attached to a green wire that should run to the heater blower fan.

So using this information you can track down where you problem is.
You won't need a partner for most of this and you won't need any spare
relays to guess with for most of this as well.

0) check to make sure that the heater blower fan is connected and that the
green wire connects to Pin 11 on T12 (green circle) in picture above.
Remove the heater blower relay if there is one plugged in.

1) Check for voltage between the pink circle and ground.
The ignition does not have to be on.
The battery should be close enough to actually use the (-) terminal for a ground.
If you see 12v this is very good.
If not goto 4)

2) short/connect pins 30 (pink) & 87 (green).
This will turn on voltage to pin 11 on T12 (green circle).
If the wires are good to the blower fan and fan is good it should turn on.
If not there is a problem with either the wires from the T12 connector
to the fan or the fan itself.


3) plug in relay and test full circuit
Turn on ignition and then pull the heater lever.
The heater blower fan should turn on.
If not there is a problem between the heater fan switch
and the relay board or you have a bad relay.

If you have a partner have them flip the heater blower switch
while you feel the relay. If you feel the relay "click", then the
relay is bad. Try another relay. If you don't feel a "click",
then the issue is in the heater fan switch wiring or the switch
itself.

The heater fan switch connects to the relay board on pin 9
on T14 (cyan circle) via a green/white wire.


--------------------------------------------

4) Check voltage on right side of red fuse.
If you see voltage here but not on pin 30,
you have something loose in your relay board.

5) Check voltage left side of red fuse.
If no voltage here. Fuse is bad.

---------------------------------------------


While not a complete diagnostic chart. It should help narrow
the problem down.

---- bill

[Trav012000]

Below is a photo of a relay board with some markings to help out in the discussion.
I'll reference the picture below.

Awesome, that'll definitely help.

On another note, you say that if you try to engage the heater, and you hear the relay click, then it's bad. I take it this is for all relays. Reason I ask is when I try to honk my horn, all I get is a click. Don't know if it's the switch in the horn or the relay though so I'll be sure to pay more attention next time.

Thanks for your help everyone.