1989 E150 4.9 C6 with AC and no aux heat or rear AC. Everything was working great about three weeks ago. We got a bout of winter weather about two weeks ago and my defroster ran more than normal. The blower stopped working. I started at the blower and connected it straight to the battery, ran great. Checked the resistor, looked fine and had no open circuits. Both these connections were a little green from corrosion (they're not sealed and they're under the hood, so it made sense). Checked power and ground at the blower connector and had both (tested with test light, can't find my VOM). Fuse in fuse box and relay beside passenger side headlight both functional. Found a burned connector on the fan switch and its connector melted. Replaced both. Cleaned all the connections and reassembled. Tested and worked fine. I repeat, tested it and it worked fine on all speeds. Reassembled dash and drove away smiling. Reached over to turn on the fan, NOTHING. Fuse is good, still have power and ground at blower connector (again, just test light, no meter).

Here's where it gets odd/dumb: Rather than using the aftermarket fan connector that's available ~$15 and adding still more resistance to these circuits, I found and purchased the OE Ford box connectors and eliminated the plastic connector thinking this would eliminate a failure point and allow heat to radiate from the connections rather than buildup and be trapped in the plastic. These 4 connectors are all grounds so I'm not concerned about a short due to them being uninsulated and they all fit the switch's terminals tightly and in a horizontal fashion so I'm not worried about them bouncing off (as I might be with a loose fit and/or hanging vertically)

I also applied dielectric grease (CRC brand, technician grade, blah blah blah I just didn't want corrosion or crap in my connections) to all the blower-related underhood connections, both the front and back side of the plastic connectors as I've done dozens of times before without issue. I've done this to the ECT sensor, 02 sensor, IAT sensor...all the sensors I've unplugged or replaced. I also use the stuff on bulbs.

So, when I pull my dash back out and check things over to find my problem, should I remove the grease or leave it? (I didn't apply it to the fan switch as that's a dusty but not damp environment and I think the grease would attract more dirt than it would need to block).

I've read of a blower motor ground terminal on the case of the computer under the passenger side dash. Can anyone elaborate on or confirm this?

Any suggestions as to what's causing my blower troubles? I have power and ground at the fan, a good running (when hooked direct) blower, good resistor, good relay, good switch, and good clean connections and everything worked fine on all speeds until a few weeks ago and then again worked great once before I reassembled things) so if I don't find anything burned or disconnected, etc I'm gonna be stumped.

 

You can't really over do it with dielectric grease, well, you can if you fill the connector too much. A little dab will do it, as the old slogan says.

A normal failure of the heater blower is the motor it's self.
Your working on a '89, which is 26 years old.
No, the blower motor should not last longer than the vehicle.
Your running AC, and that fan motor is working all summer on high.

I know you wrote that you "tested it" direct to the battery, But, when installed, your going thru relays, connectors, resisters, that all take some voltage away from the circuit.

I think a simple solution is to replace the blower motor itself at this point.

You also wrote that the fan switch connector was melted?
You replaced the connector, and wired direct to the switch?
Are the wires them self in good serviceable condition? or are the wires burned out?

 

Hi,
The ground strap on the passenger side dash appears to be for RF static affecting the ECU which is mounted directly under the blower box. RF and electrostatic charges from the blower motor and air moving through the vents could cause problems for the ECU so Ford used a braid to ground. Mine shown here is to the sidewall but it is supposed to be fastened to the bottom of the dash, I think?

I had an intermittent blower problem, turned out to be a melted connector under the hood feeding the blower. I cut the connector, added blade connectors and fixed it. Due to the high current used by the blower, any resistance in the connections is a problem, both for voltage drop and heat.



ECU ground strap.



jim

 

I've read way more stories of a failed resistor, switch, relay, etc than the blower itself. Mine worked fine before the issues and never made a bad noise, ran slower than I'd expect, etc and when it was hooked direct it was nice and quiet and smooth, same the 1 time it ran since I replaced the fan switch and its connectors.

The blower worked both direct to battery and in the complete circuit.

Yes, I plugged the fan switch wires onto the fan switch with OE Ford connectors but not the plastic terminal holder. The wires are good. About a 1/4" of the permanent ground was heat-marked so I cut it off, stripped, and connected to good clean, virgin wire.

If you know a simple way I'm all ears LOL

EXACTLY my thinking in not adding butt connectors just to get back the plastic terminal holder. Loose connections and excessive resistance are the sources of the heat that seem to plague these old girls