Heater Fan

[Mike Quillici]

I replaced the heater fan today, and while I had it disconnected, I checked the voltage on the connecting wire. Out of the four positions for the fan speed indicator, one results in 0 V, two generate ~12 V, and one yields ~7 V. The fan is only operational in two of the four positions. If I remember correctly, "Hi" is the position that yields ~7 V. What could be causing this? Could the switch be defective? Incidentally, the third bolt on the hood hinge is an absolute pain in the butt to get out. Is there an easier way to deal with that about which I was not aware?

Also, how often do the heater control valves, which control coolant flow into the heater core go bad? Regardless of whether or not vacuum is applied, I can't seem to get it to open and get warm coolant into the heater core. If I have to replace it, it's only a $20 part at Autozone.

Thanks all.

[mrein3]

It has been a while but a couple of years ago I swapped out my non-AC heater stuff for AC. The plug for the fan switch I got from my used parts hunt was slightly melted and some of the wires messed up. When junk yarding for another harness I discoverd most of the AC switch plugs are melted up the same way.

So I rebuilt what I had. I ordered a new switch, new plastic switch plug, got some wire ends at NAPA, and some colored wire to match the wire diagram.

REALLY long story short, there is a set of one, two, or three resistors after the switch to step down the amount of voltage running to the fan. This controls fan speed.

I can't remember what the numbers were, and you didn't specify if you had AC or non-AC, but I'm thinking I had 3V, 6V, 12V, and 12V. One of the 12s turned on a relay that really spins the fan.

Regarding the heater control valve - they do go bad. If yours is original I'd just replace it and move on.
However I think they default to open. In other words when they are broke they are open. Maybe somebody else will chime in here on that one.

[Mike Quillici]

I will check out what's going on with the back of the switch tonight. Thanks for the info! And yes, I have an A/C setup. The position that flips that relay is the one that doesn't do anything. I figure one position is off, one is low, one is medium, and one is high (flips the relay). That's my theory at least.

Thanks!

[mrein3]

Originally Posted by Mike Quillici

I will check out what's going on with the back of the switch tonight. Thanks for the info! And yes, I have an A/C setup. The position that flips that relay is the one that doesn't do anything. I figure one position is off, one is low, one is medium, and one is high (flips the relay). That's my theory at least.

Thanks!

When I re-did mine I simply added a new relay in place of the factory one. Personally I think the factory wires were undersized so when you were really pulling amps through them they got hot and melted behind the switch. (I know with a relay this shouldn't happen but I'm thinking the resistors in-line built up a lot of heat which may have caused the problem)

I just did a search and lifted this diagram off this site. I hope it helps. It helped me when I did my conversion.

[Mike Quillici]

When I switch to "Hi," I can hear the relay click, but the motor just stops. Do you think that replacing the relay might fix this problem?

[Bus Ted Knuckle]

Originally Posted by Mike Quillici

When I switch to "Hi," I can hear the relay click, but the motor just stops. Do you think that replacing the relay might fix this problem?

yes

[fixit-p]

Before you replace the relay check the wire I highlighted on the diagram for power, the fact that the relay clicks and cuts the motor verifies that the relay is actuating (changing over) if the wire I highlighted has power at the relay the contacts in the relay maybe bad but if there is no power that is the problem.

[Mike Quillici]

I'm reading this on an iPhone. Is that a 12 gauge orange wire?

[fixit-p]

Thats what it looks like 12ga. orange and it should be plugged into the CIG port on the fuse block

[Mike Quillici]

CIG. Okay. I will check it out! Thanks.

[Mike Quillici]

I checked the 18 gauge orange wire, and that has 0V at all positions except "Hi." Is that the wire that you meant? When I remove that wire from the relay and put the fan in the "Hi" position, the fan comes on at the same speed as when in low. But when I reconnect it to the relay, the fan cuts out again.

[Bus Ted Knuckle]

Originally Posted by Mike Quillici

I checked the 18 gauge orange wire, and that has 0V at all positions except "Hi." Is that the wire that you meant? When I remove that wire from the relay and put the fan in the "Hi" position, the fan comes on at the same speed as when in low. But when I reconnect it to the relay, the fan cuts out again.

with a faulty relay, you will have low speed, but not higher speeds.

[Mike Quillici]

Also, the 12 gauge orange wire shows about 8.7V in all positions. I'm thinking the relay is kaput. . .

[fixit-p]

The 12 GA wire should have full battery voltage not 8.7 probably due to high resistance a quick test would be to eliminate the relay by unpluging it and jumping the 12OR and the 12PPL wires or you could unplug the 12OR wire at the fuse block and insert full bat voltage there.

[Mike Quillici]

I think I figured it out. I pulled the 12 gauge wire out of the CIG port on the fuse box, and the connector was partially melted. So that explains the high resistance in the orange 12 gauge wire. I'll run a new wire tomorrow.

On a separate note, do both the cigarette lighter and the 12 gauge orange wire plug into the CIG port? That seems weird. Right now, the cigarette lighter and the orange 12 gauge wire are spliced together, which probably explains the melted connector.

I'll let you know if it works tomorrow.

[Mike Quillici]

Alrighty. I replaced the 12 gauge orange wire that runs from CIG to the relay, and I now have 12V at the relay. So that's an improvement. However, the fan still cuts out on "Hi." The relay clicks like it always has.

What???

Well, if nothing else, at least the fan is now getting full voltage, but I still don't have full fan!

[fixit-p]

Replace the relay

[Mike Quillici]

I replaced the relay today. I now have 3 heater speeds. Thanks everyone!