Help! How can I get my heater fan to stop running????

[kna4977]

Originally Posted by jhow66

Clicking sound under hood is compressor clutch kicking in when you turn the fan switch on with all the levers to the left. Normal. Do you still have the anti-diesel relay as shown in the diagram? Do you have #14 brown (dotted line) line coming off fuse panel to blower switch? (as shown in diagram)

This system never had an anti-diesel relay, but the new harness has a connection for one. I have all the wires in the right place. I have quadruple checked it.

I did make some progress. I took apart the control switch and cleaned the contacts. When it came apart, it kind of exploded on me, so I was not sure how to put the copper T-shaped piece back in (horizontal piece toward the top of the switch or toward the bottom of the switch), so I tried it both ways. With the horizontal piece toward the top, I was able to have either off or high, but the switch was very sensitive, and even the smallest amount of jarring would switch it from off to high. The other way I have low or high, but no off. Again it's sensitive that way too. I believe since I have made this progress, it would be best if I replaced the control switch. What do you think? Bad relay and control switch??

[jhow66]

Just try the switch first.

[kna4977]

Originally Posted by jhow66

Just try the switch first.

I've replaced the control switch and the relay, and still when the switch is at Hi = fan at low speed, everything else (Off, Low Med) is high fan. Any suggestions??

[kna4977]

Does anyone have a picture of the fusebox and all the wires connected to itin a truck where everything works right? If so, I would really appreciate it.

[hotrodhomi]

check the FAQ for the diagramn

[kna4977]

There's a diagram posted previously in this thread. I tried the FAQ, but didn't see the diagrams.

[hotrodhomi]

Do you have a DMM? Do you know ohms law? E=I*R

[kna4977]

Originally Posted by hotrodhomi

Do you have a DMM? Do you know ohms law? E=I*R

I don't have a DMM, but do have access to one. I'm not sure that if I had it in hand that I would know what to do although I have used one before and knew how to use it then. I should know Ohm's law, but at present my memory is failing me. Please remind me about it if possible.

[mrein3]

Originally Posted by kna4977

I don't have a DMM, but do have access to one.

It really is time to get a DMM out. I had to when I put my AC set-up in. Just print out the wiring diagram posted eralier and start checking voltages.

That is EXACTLY what I had to do.

[mrein3]

kna4977,
I just read your other post about the orange wire and how as soon as you hook it up you get high speed.

Now it all makes sense.

One of two things is happening.
1. Your relay is stuck in the accessory gets power position.
2. You are always supplying voltage to the signal side of the relay, which closes the contacts which powers the accessory you are trying to get lots of power to.

Since you said you already replaced the relay once, I'd look real hard at the wires coming out of the switch. In all likely hood you have #2 above happening.

If memory serves, that orange wire is a big, 12 gauge or so wire. It is meant to carry lots of current to the fan for the high-speed selection. The cigarette ligher circuit is a big beefy sucker that can carry lots of amps.

When I wired mine I made a seperate circuit off of a newer relay. My "new" circuit gets 12+ volts right off the battery and is switched on through a new relay. The "orange" wire off the battery has an in-line 20 amp fuse in it for protection. And yes I did make this new wire orange which on most GM vehicles of this vintage means "many amps worth of 12 volts in here".

Now I'm not saying you should re-wire everything. You just need to check the wires coming in and out of that switch. The best way to do that is to get the switch out of the control panel and let it dangle. Then you can select different speeds and test voltages from the back of the connector on the back of the switch. Judging from your other post I would say you are going to find 12 volts coming out of there and heading to the relay in every position of the switch that you get high speed out of.

One other possibility...
Did you wire it correctly? Is that orange wire connected directly to the purple (big wire to the fan motor) wire?

[kna4977]

If I do find 12 volts at each position, what does that mean?

Also, if the orange and purple are connected, what does that mean?

[krue]

I don't remember Ohm's law, but the equation reads as
voltage=current x resistance

[67chevy2wd]

Volts = Amps x resistance
Resistance = volts / Amps
Amps = Volts / Resistance

[jhow66]

Good info. Here is the way the system works:
1--Large ORANGE wire from fuse panel goes to the relay only.
2--BROWN wire from fuse panel supplies power to fan switch.
3--With fan switch in off position there should be no power to any wire on fan switch with ignition OFF.
4--With ignition ON and fan switch OFF there should power on BROWN wire only.
5--With fan switch on HI there should be power on Orange wire from fan switch to relay-this cause the relay to close and rout power from LARGE ORANGE wire from fuse panel out thru the PURPLE wire to fan motor for high speed.
6--With fan switch in low or med.( yellow or blue wire) the power from the fan switch is routed to the resistor and back out of it on thr DARK BLUE wire to relay onto the purple wire to fan motor.
7--It is routed this way for both heat and AC ( for AC all levers are to the left so when the fan switch is moved to any speed the AC compressor clutch is engaged by a switch on back of heater box (it is closed by one on the lever cables when they are all to the left).
8--Now for the solution (I hope)--The BROWN wire from fuse panel is inserted into the wrong hole in the connector that plugs into your fan switch and has power on it with ignition switch off (this wire (BROWN) should be dead with ignition off).
9--To test, remove brown wire from fan switch-fan should not run with ignition on or off. With ignition still off check to see if you have power on the Brown wire. If you do the Brown wire is probable shorted behind your fuse panel. (fuse panel is held in place by 2 screws--easier to remove if you take the firewall connector under hood off first)
10--Also with ignition on or off there should be power on LARGE ORANGE wire on relay ONLY with fan switch OFF.
11--I will disconect my fan switch tomorrow and draw you a diagram of where each wire goes if you think this will help.
12.--disclamer-all the above info carries no warrenty.

[kna4977]

[/B]

Originally Posted by jhow66

Good info. Here is the way the system works:
1--Large ORANGE wire from fuse panel goes to the relay only. CHECK
2--BROWN wire from fuse panel supplies power to fan switch.CHECK
3--With fan switch in off position there should be no power to any wire on fan switch with ignition OFF.CHECK
4--With ignition ON and fan switch OFF there should power on BROWN wire only.CHECK
5--With fan switch on HI there should be power on Orange wire from fan switch to relay-this cause the relay to close and rout power from LARGE ORANGE wire from fuse panel out thru the PURPLE wire to fan motor for high speed. SHOULD THE IGN BE ON OR OFF? ALL WIRES HAVE 12 VOLTS HERE WHETHER THE IGN IS ON OR OFF, AND THE FAN CUTS OFF. ALL EXCEPT PURPLE WIRE ON RELAY HAVE 12 V AS WELL THEREFORE THE FAN CUTS OFF, IT JUST SHOULDN'T
6--With fan switch in low or med.( yellow or blue wire) the power from the fan switch is routed to the resistor and back out of it on thr DARK BLUE wire to relay onto the purple wire to fan motor.LOW OR MED ALL WIRES ON SWITCH HAVE 10V EXCEPT ORANGE W/IGN ON. IGN OFF NO VOLTAGE ON ANY WIRE. ALL RESISTOR WIRES HAVE 10V W/IGN ON. NO VOLTAGE WITH IT OFF. ALL ON RELAY HAVE 10V EXCEPT THE SMALL ORANGE WIRE W/IGN ON WHICH HAS 0V. THE ORANGE AND DK BLUE WIRES HAVE NO VOLTAGE W/IGN OFF THE BIG ORANGE AND PURPLE BOTH HAVE 10V THIS IS WHY THE FAN RUNS
7--It is routed this way for both heat and AC ( for AC all levers are to the left so when the fan switch is moved to any speed the AC compressor clutch is engaged by a switch on back of heater box (it is closed by one on the lever cables when they are all to the left).THIS SWITCH WORKS AS IT SHOULD
8--Now for the solution (I hope)--The BROWN wire from fuse panel is inserted into the wrong hole in the connector that plugs into your fan switch and has power on it with ignition switch off (this wire (BROWN) should be dead with ignition off).THE BROWN WIRE IS DEAD WITH THE IGN OFF, BUT THE FAN STILL RUNS. THERE IS ONLY ONE PLACE FOR IT TO GO IN THE CONNECTOR BESIDE THE ORANGE WIRE WHICH IS IN THE CENTER BESIDE THE YELLOW WIRE. THE LIGHT BLUE IS ABOVE THESE
9--To test, remove brown wire from fan switch-fan should not run with ignition on or offBUT IT DOES, THIS IS THE PROBLEM. With ignition still off check to see if you have power on the Brown wireTHERE IS NO POWER ON THE BROWN WIRE, BUT THE FAN STILL RUNS BECAUSE THE PURPLE WIRE HAS VOLTAGE. If you do the Brown wire is probable shorted behind your fuse panel. (fuse panel is held in place by 2 screws--easier to remove if you take the firewall connector under hood off first) IF YOU CAN DOWNLOAD THE TEXT DOCUMENT IT WILL PROVIDE A BETTER EXPLANATION OF THE VOLTAGES THAN THE WORDS LISTED ABOVE AND CAN HELP YOU COMPARE AND CONTRAST WITH YOUR SYSTEM. I TRIED TO POST IT DIRECTLY, BUT THE FORMATTING MESSED UP THE CHART
10--Also with ignition on or off there should be power on LARGE ORANGE wire on relay ONLY with fan switch OFF.THERE IS ALSO POWER ON THE PURPLE WIRE, THIS IS THE PROBLEM
11--I will disconect my fan switch tomorrow and draw you a diagram of where each wire goes if you think this will help.THAT WOULD BE GREAT
12.--disclamer-all the above info carries no warrenty.

[mrein3]

You need to start at the fan. The purple wire. With the ignition off, it is getting power from somewhere. You need to find that.

Follow it back. With ignition off, this should never have power.

[kna4977]

The harness I have has the wires for the anti-diesel relay. Since the system never had this relay, do I need one since the harness has a plug for it?

Also, what does this part do?

I will check on the purple wire.

[kna4977]

The anti diesel relay wiring has no power to it. I don't understand how the purple wire is getting current at the wrong time because the wire only runs from the relay to the fan unless the problem is within the relay, which is new. I switched the positions of the double orange wire and the purple wire on the relay, and now instead of high cutting it off, it puts it on low producing a voltage at the resistor of 2 volts. All the other positions produce high fan. The relay only clicks when it is placed on high. I am stumped.

[jhow66]

'4977 I did not to get your info before dark (had company)-will get it for you tomorrow. Sorry.

[jhow66]

Here is how mine is wired:

[kna4977]

Originally Posted by jhow66

Here is how mine is wired:

Hey, thanks for taking the time to do that for me. It seems to have helped a lot, although I'm still not quite there. So I took the relay wires out of the harness and tried a lot of different scenarios as listed above. I then put the wires back into the positions shown in the picture, and although it doesn't look any different than what I started with, it must be.

Now high fan is high fan, and the fan doesn't blow immediately when I connect the battery like before, but every other position (off,low, medium) is off. Any suggestions?

I'm taking it in tomorrow to have it charged, and will most likely let them fix it, but I would still like to know what is wrong.

Thanks again for your help!

[mrein3]

Check the voltage before and after the resistor block with the fan on medium and low. You may have fried those resistors.

[jhow66]

Did you check the resistor when you were installing the AC-was it plugged up? Sounds like what Mrein' says.

[kna4977]

Originally Posted by jhow66

Did you check the resistor when you were installing the AC-was it plugged up? Sounds like what Mrein' says.

Yes I checked it. It seemed to work just fine during the different relay wiring scenarios. I was able to get low and medium speeds out of it. I took it to get charged today, but they have not been able to figure it out either.

He did ask me if there were 2 different A/C harnesses available, and I told him there was one with the anti-diesel relay and one without.

Are replacement resistors available for these vehicles?

Could the fact that I have the harness for the system with the anti-diesel relay hooked to a system that doesn't have it be causing the problem, or does that matter?

thanks

[jhow66]

Yes you can buy resistors. After studying the diagram there should be no differance in either harness as you have nothing pluged into it. Try this:
1--Ignition switch on-fan switch on low- there should be power out of fan switch on yellow only.
2--with above still in the same position go to relay and check for power on dark blue wire-if so fan should run slowly-if no power on dark blue wire the resistor is bad.
3--same as #1 with fan on medium-power out on yellow and light blue both-check as in #2
4--same as #1 with fan on high-power out on yellow,light blue and small orange-if you have it this way, fan switch is ok.
(either your resistor is bad or not plugged up if the above checks out.