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Strange goings on with my 76 CS w/factory air. Without the key in the ignition, if I move the heater lever to Defrost, I can hear the blower motor. Moving the fan lever to full gives me full flow. Now, if I put the key in and move it to the on position, the blower motor quits. Kind of frustrating when your window is fogged up.
Should I look at the ignition switch first or the blower motor?
Without a key, nothing works except the blower motor in the Defrost position.
Accessory or On positions kill the blower but energizes everything that should be energized.
Bob
Not an electrical expert, but sounds like maybe the motor is wired wrong. Sounds like you have a always on power source to the hot on the blower, and the ground is tied to the ignition power. When it is off, the ignition power is making a ground, causing the motor to run, when the ignition is on, it puts power on that ground. Would think something would blow, but I could be way off on my idea.
'76 with factory air has a blower motor relay (behind the dash I believe). It will be connected between the AC mode switch and the blower speed switch with three wires, Yellow w/red, Orange, and red w/black.
with they key off, check the voltage on the Yellow with red stripe wire. That is the wire that should energize the relay and apply power to the blower speed switch input.
Did this ever work correctly? the symptoms you describe would happen if the relay was replaced with a normally closed instead of normally open relay.
Update:
Seems the blower will run without key in any heater lever position except 'Off'.
(Runs in A/C, Hi/Lo, Heat, Defrost)
Blower motor sounds like junk when I just tried it.
Need to replace the heater core so I'll be adding a blower motor also. Would be nice to find this gremlin prior to installing new blower as an install test would have failed and I would have blamed the new blower.
I'll pick up a volt meter and start probing.
Under the dash I go !
'76 with factory air has a blower motor relay (behind the dash I believe). It will be connected between the AC mode switch and the blower speed switch with three wires, Yellow w/red, Orange, and red w/black.
with they key off, check the voltage on the Yellow with red stripe wire. That is the wire that should energize the relay and apply power to the blower speed switch input.
Did this ever work correctly? the symptoms you describe would happen if the relay was replaced with a normally closed instead of normally open relay.
After digging my truck out of 2' of snow, I pulled it into the garage and attacked my blower motor problem. I found the relay you mentioned but I have no way of knowing if it's normally open or normally closed. Here's the specs on it (pic).
Is there an online reference for the code numbers on this relay? I've checked wiring diagrams but see nothing with these code numbers.
Thanks
Bob
I think that is the correct relay. What was the voltage on the wire I mentioned...I would check it both with the key on and the key off. I assume the blower stops when you unplug the relay?
dlburch
Misplaced my multimeter a while ago so I have to hit the parts store for a new one.
The blower definitely quits when I unplug the relay.
I'll post my results with the multimeter after I hit the parts store.
Thanks for your continuous help.
Bob
The source of my problem with the blower fan was the relay.
PO had it mounted without a good clean base for ground (paint free).
I sanded a spot under the dash to bare metal, mounted the new relay and everything works according to Henry Ford.
Thanks for all the help...you guys are alright
Bob
Blower motor sounds like junk when I just tried it.
Need to replace the heater core so I'll be adding a blower motor also.
If it's working but just noisy, it might just be leaves/debris built up in the housing that you can clean out when you change the heater core without having to replace the motor.
I was able to pull the heater motor with squirrel cage still attached. I removed one bolt holding the dash at the lower right corner. Pull the bottom of the dash out while you swing the evap up and it gives you more space.
After digging my truck out of 2' of snow, I pulled it into the garage and attacked my blower motor problem. I found the relay you mentioned but I have no way of knowing if it's normally open or normally closed. Here's the specs on it (pic).
Is there an online reference for the code numbers on this relay? I've checked wiring diagrams but see nothing with this ID engineering number.
D2LY-14512-A .. Safety Relay / Marked: D2LB-14C690-AA .. D5AB-14C690-AA or BA or CA / Obsolete
Misc. applications: 1975/79 F100/350 & 1978/79 Bronco with factory A/C // 1975/79 Econoline with trailer tow package // 1977/78 LTD with power windows // 1977/80 Granada/Monarch with sun roof.
CARPENTER NOS OBSOLETE PARTS in Concord NC has 27 = 800-476-9653.
GREEN SALES CO. in Cincinnati OH has 34 = 800-543-4959.
12-11-2014, 09:32 PM
