1976 Mark IV Blower Only Working On Maximum Setting

Bill-
I have a 76 Mark IV Lipstick Edition with 15k actual miles. I have worked on Lincolns for the last 25 years, and enjoy the challenge. The blower will only work on maximum. All vents work, defog, vacuum open and close as they should. I ordered a blower relay from Lincoln Land, fitted it just the same. The terminals are like new and clean. Like most low miles cars, I do not know weather to use it more and see if it springs back into life, or investigate more. The car is like new all original everywhere you look. Your thoughts would be appreciated.
Kind regards,
Dave in the United Kingdom
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Hi Dave –
Some of these electrical problems can be challenging at times. The function of the blower relay is to connect the blower motor directly to the battery through a fuse link only when Max Blower is selected. When you select a Lower speed the relay is de-energized and another connection is made between two wires within the relay for all other speeds. These two wires can be temporarily jumped together ( with the relay disconnected ) as a test for proper continuity inside the relay. The wire colors to jump should be, The large gauge Orange with a Black tracer and Light Green with a White tracer. Unplug the relay and jump these two wires together temporarily as a test. Turn the key to the on position with the blower switch on a lower speed. If the blower motor now begins to operate with these two wires jumped but is non operative when the plug is again attached to the relay, you could have faulty relays. If the blower still does not start you will need to trace the blower circuit as per the wiring diagram. In either event please contact us so that we can correct a possible faulty relay for you or help you proceed to the next diagnostic step. Do you have a proper wiring diagram for the HVAC system for your Mark IV ?
Sincerely,
Bill
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Bill –
Unplugged the replacement relay, crossed the two wires, black and orange. Green white, turned ignition on, nothing, not a flicker. Still no low or high.
Regards,
Dave
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Hi Dave –
It sounds like you have jumped the correct wires The first wire actually should be orange with a black stripe though. On the Lower speed setting the green wire with a white stripe should have power from the system unless the engine is cold and the ATC is calling for heat. Check for power at that wire with a warm engine and the control set on the lower speed. If there is power at that green/white wire try the jump test again. There should be two 20 amp fuses in the fuse box for the climate control that can be checked with a 12 v test light. If still no power at the green / white wire (with a warm engine running and the control set on a lower speed range), a wiring diagram will be necessary for you to trace the power path properly. As an added test, the relays can easily be bench tested with the use of “continuity tester” applied to the two pins on the relay that the above two previously jumped wires attach to on the relay. Do you have a correct wiring diagram to aid you in further testing?
Sincerely,
Bill
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Bill –
Problem sorted. Bad connection at the back of blower switch. Pushed it well home ,and working great on all settings. Thanks for your help and assistance.
Regards,
Dave
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Hi Dave –
We are happy that you have found and corrected your problem. Your next step would have been to trace the power path on the green/white wire from the high blower relay plug using the wiring diagram. The loose connection at the switch would have been found during the diagnosis. Good work and perseverance on your part proved to be successful in correcting this issue. We were glad to assist.
Sincerely,
Bill