Howdy all,

1983 f150, factory a/c, auto with overdrive, inline 6, standard cab probably with towing package.

In August I bought the old girl as a project truck and have worked out many of the bugs, but for the life of me, I can't find out why the blower is getting no power. I have replaced the blower; old one had a ton of bearing noise. Also the resister; heavy rust and multimeter suggested the little, normal looking resister had failed. Multimeter tested both the blower switch and the off/ac/vent switch were good. Fuse also tested good. I am unsure if there is a relay, but if there is, I cannot find it. I have checked the continuity of everything I can think of without finding a problem. The ONLY thing that has caught my attention is the connector that plugs into the back of the vacuum plenum that controls off/ac/vent: it has no continuity between any two of the connectors. Could that be part of the problem, or am I barking up the wrong tree?

Thanks in advance for any help.
John

 

Even if the resistor pack goes for a dump you should still have the high setting.

Just to be clear you are not getting any power at the blower when it is set to for example defrost ?

On the heater controls (not the speed switch) the output to the blower is the Brown/ Orange wire that should have power in for example defrost. If it does repair the circuit between there and the blower motor.
If it does not have power, check for power on the Brown/White wire if it has power the heater controls are faulty. If the Brown/White does not have power the circuit between there and the fuse is faulty repair the circuit.

 

Here's a diagram for a 1981. They are all mostly the same through the years.



Here's a 1985 same circuit.

 

Forgive me, but between 38 years of crud and my poor color vision, picking out wires is tough. But I have done tests using a more plodding method. I checked the controller switch and determined the bottom two contacts (left side of the connector below) have continuity in all selector positions except OFF. The top two contacts (right side in photo) connect ONLY for A/C high and low, and defrost. If I understand correctly, the left/bottom contacts go eventually to the fan. The right/upper contacts control the A/C clutch.


If I understand your post, the brown/orange (second from left) has power in all selections except off. Based on the continuity checks, there should be power flowing between it and the darkish/white (leftmost) contact. When I test both of the left/bottom two contacts, neither has power. If I understand correctly, that means a problem exists between the plug and fuse box. Aside from taring the bundle apart, would a jumper between the plug and the fuse test for this problem?

 

In both diagrams, two single wire C603 connectors are right above the blower. My blower has 2 wire connectors. Are the C603 comparable to my setup?

 

One thing I failed to mention is that the compressor has been removed; it was disconnected when I got her, so I removed it since I figured it likely was bad. I haven't bothered getting a new one until the rest of the system is working.

 

Sorry, last question...for now.

There is one strange looking plug I haven't found out what is it for. It is in the bundles near the control panel and wondered if it was part of the problem:



In the second photo, it is just above the vacuum connector.

 

The diagram shows a C603 connection above and below the blower in the diagram. That means there are two wires in C603. If you look at the diagram, the top wire is orange, the bottom wire is black. These are probably different colors now that the motor has been changed. Feeding these wires are a brown/orange on top and a orange/black on the bottom.

You are better off getting yourself a testlight, and poking around lookng for voltages instead of doing continuity checks on individual components.

 

Continuity checks are fine but that does not tell you if you actually have power.

Electrical diagnostics procedures need to be followed or you are just going to chase your tail. And we can't help you.

So lets do this again. Using your below pic..

Step 1

Test for power (12V or batt voltage) on the wires labled number 1 If no 12V is present on either wire repair the circuit to the fuse block or replace the fuse. If power is only present on one wire report back.

If power is present on both wires go to step 2


Step 2 again using the below pic. Plug that plug back into the heater control panel and back probe the number 2 wire to see if power (12V batt voltage) is present. with the slider in the defrost position.
if no power is present the heater control is faulty. Replace heater control. If power go to step 3

Unplug the blower motor at connector C603, On the harness side. (not the side that goes to the motor) Check for power on the Brown and orange wire. If no power repair the circuit , if power the issues is either a faulty motor or it's in the control side (Ground)

After doing these tests report back. Again check for power, if you want this problem resolved you HAVE TO follow the directions..

Anf BTW Dave none of your attachments are showing up for me. No idea why either..

 

Huge thanks to you both for being patient. I don't know if my frustration with my minuscule knowledge of electrical systems is showing, but if it is, I apologize.

I will get back to it tomorrow and report back.

 

Thanks to your suggestions, I have made progress.

Test 1 Power the #1s: No power to either of them, but power to fuse. I put a jumper from the protected side of the fuse to #1 and got power. So first problem identified. I left the jumper installed and moved to step 2.

2. Without the jumper no power; with the jumper, heater control passes.

3. With jumper, Red/Brown side of plug has power, but when blower plugged in, motor does not turn. Motor check fine when jumped directly to battery. Added a jumper from the other C603 wire, fan ran.

Other checks:

Ignition switch cuts supply to circuit in off position.
Fan speed switch varies speed correctly.
The slider does NOT shut off the fan when in the off position.

 

OK sort of a cluster but i'll try to decipher this.

Question 1. What exactly did you mean by "jumper from the protected side of the fuse to #1 and got power" ?
. There is the feed side of the fuse. From batt to the fuse.
And the load side of the fuse. Fuse to the blower motor.

Question 2. Is their power on the load side of the fuse ?

Question 3. Is the fuse good ?

Question 4. So I think what you are saying is the fuse has power on both sides but no power on the Brown white is that correct ? Are you sure you have the right fuse ? (just a double check)

If you have power on the feed and load side of the fuse but no power on the Brown and white either repair or jumper it for now and leave it while we diagnose and don't mention the jumper from here on out.


Question 5. Sounds like you had the power to the Brown Orange wire (It's not Brown and Red) through the heater controls when the brown and white was jumped is that correct ?

Question 6. there was power at the Blower motor C603 connector on the Brown and Orange wire when the brown and white was jumpered.?


If you for sure have power at the blower motor connector on the brown and orange and it still does not work, the issue is on the control side (ground) and we will have to diagnose the ground side of the circuit.

 

Remember the blower motor sometimes does not have a true ground. It only has a true ground when the speed selector switch is in high. Otherwise, the ground for the blower motor goes through the resistor pack. So once you hot wire the selector with the jumper, and get power at the motor, do you have a ground at the motor? You can jump the other side of the motor to ground and see if it runs. If it does you need to find the grounding problem in the resistor/speed switch network.

 

Sounds great!

 

Ok so now we have the power side sort of sorted out, you do have a fault between the fuse and the brown/white wire but have a jumper in place. That can be fixed later. For now, we will concentrate on the ground side of the blower.

Step 1.

First, make sure fan speed switch is plugged in and in the high setting. Back to Connector C603 at the blower motor. Unplug the blower motor. On the harness side of the connector, we are going to test continuity between Orange and Black wire and ground. Making sure the fan switch speed switch in the high setting. You should have continuity to ground, if you do have continuity to ground, report back as something is amiss as the fan should run with the switch in the high setting. If you do not have continuity to ground go to Step 2

Step 2

Unplug the Heater Fan speed switch. On the Orange Black wire terminal on the harness side of the connector, Install a jumper wire, from the Orange Black wire terminal on the connector to a good chassis ground make sure the connections are solid. Now check to see if you have continuity at connector C603 on the harness side of blower motor connector between Orange and Black wire and ground. If you have no continuity to ground repair the circuit, If you have continuity to ground. Go to Step 3

Step 3

Remove the jumper wire from the Orange Black wire terminal on the harness side of the fan switch connector. With the fan switch still in the HIGH setting, test for continuity through the switch from the Orange Black wire terminal on the switch to the Black wire terminal on the switch. If you have no continuity from the Orange Black wire terminal on the switch to the Black wire terminal on the switch replace the switch, If you have continuity through the switch Go to Step 4

Step 4

With the Fan Speed switch still unplugged Locate the Black wire terminal on the harness side of the fan switch connector and check for continuity to ground. If you have no continuity to ground repair the circuit, If you have continuity to ground redo the above tests as something was not done correctly as the fan should run with the fan speed switch in the high setting.