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August 20, 2018

1979 Mark Engine Fire - AC/Heat Related Issues

Hello Bill,

My '79 Mark V had an engine fire. I got the fire out with no damage to the original paint. It burned a lot of the vacuum hoses and wiring. I have '79 parts car that I was able to get the wiring harness out of and replace the burned harness. I replaced all the burned vacuum hoses, a very big job. Now after the engine is warmed up and the heater levers in the heat mode, the heater fan will not run when turned on. Also with all the heater control levers off the defroster is on all the time with no fan. This heater system is a very complex system to work on. I have the Ford factory shop manual and it's not any help.

Lyle

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Greetings Lyle -

Some of these Automatic Temperature Controls sure can be tough to diagnose and repair if you have little experience. Sometimes the experience does not help either especially if a fire has occurred.

You do not mention if these malfunctions occurred before or because of the fire. In any case we can offer the following suggestions. The factory service manual is excellent in all respects for troubleshooting and understanding how the system works. I don't know which section you are reading but in Volume Three the 1979 Mark V ATC section begins on page 36-74-1.

An under the hood fire that damaged rubber vacuum hoses as well as electrical parts can only repaired by someone there on scene with the correct manuals and so on because I cannot see the extent of the damage at all from here. It would appear from your description however that you still have an existing vacuum problem or two. The shop manual shows the complete vacuum diagram along with the colored tracers on the hoses as well as a chart that shows what vacuum is sent out to the vacuum actuators with the various positions of the control switch.

No blower in the HEAT position is a common issue and is caused almost always by a faulty EVR (Electro Vacuum Relay) unit that is located under the dash above and to the rt. of the transmission hump. Its operation and installation drawing is well explained in that same shop manual. Be advised also that wiring for the EVR operation runs to the top of the engine and to the Temperature Sending Unit at the rt. front of the 400 engine. This relay functions to hold the blower motor inoperative in the HEAT position when the engine coolant is cold and the ATC is calling for heat. A fire could possibly have shorted this wire to ground so that EVR is in the cold engine mode with the control in the HEAT position. If you suspect but can't test the EVR yourself, we can offer test it for you at Lincoln Land.

Sincerely,

Bill

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Hi Bill,

I have looked at the section 36-74-1 in the manual. The blower is working OK now. I guess the engine wasn't warmed enough before.

Everything points to a vacuum leak. The manual says if there is a vacuum leak the defroster will go to the default on mode but I sure can't find it. There's no hissing noise anywhere that I can hear.

My son is a master auto mechanic so I'll ask him to help me.

Thanks for the help.

Lyle

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Hi Lyle -

Great! You are indeed lucky. Sounds to me like a good idea. Your son will understand the manual and the diagrams. Keep in mind that all vacuum leaks cannot be heard easily and some components need to be tested with a hand held vacuum pump that has a built in gauge. We have most parts for you already in stock to repair this system. We wish you a speedy repair.

Bill

August 16, 2018

1979 Mark V Seat Belt Chime Inop

Hi Bill,

I'm trying to repair the seat belt chime in my Mark V. I removed the chime and cleaned the rod that hits the metal bar that makes the chime noise, also bench tested it with 12 volts and was unable to make it work. I looked in the 79 shop manual and read that the chime works through a thermal timer that gets ground from the left seat belt re-tractor switch. I assume that switch is located on the seat belt re-tractor that is mounted on the floor. I removed the floor mounted seat belt re-tractor and found a plug on the re-tractor with no wire going into it. The "fasten belts" light on the dash is also inoperative and I'm wondering if the seat belt re-tractor switch is the culprit or one of the culprits for the chime and "fasten belts" light not working. Also did i bench test the chime correctly or is there a different way to do that.

Thanks,

Matt

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Hi Matt -

Some of these electrical problems can be time consuming to diagnose and repair. You may need the correct wiring diagram to do this properly.

I cannot tell you if you have done the chime test correctly at this time because I do not know how you tested it. Please send me the page number from your 1979 FoMoCo manual that you used for this test.

During this era many owners had the chimes and buzzers on their vehicles disabled and some of the parts were subsequently discarded because they found the sound annoying and distracting.

If you wish we can offer to "check out" your chime unit here at Lincoln Land if you are unsure of it's condition.

Sincerely,

Bill

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1977 Mark V Headlight Doors Always Down...

Bill,

I have a 1977 Lincoln Continental Mark V. I am having an issue with my headlamp covers. They stay down all the time, when the car is off, car is running, when the lights are on, and when the light are off. The only time the covers lift up is when I manually unplug the vacuum lines under the hood. But when I plug the lines back together, they shut again. So I have been manually swapping the lines when I drive at night. What do you think is causing the issue of the covers always being down unless the lines are physically unplugged or swapped?

Thank you,

Connor

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Connor -

Does your Mark have the Autolamp option? Without this information or any meaningful diagnosis information as to what you have checked so far with your shop manual no one can be close to pinpointing the cause. However, one popular fail item with these symptoms is the headlamp vacuum control solenoid module which should be located behind the left kick panel. If you indeed have the correct shop manual as you indicate the operation and diagnosis should be included. Also it has been previously discovered on other vehicles that some previous owners have actually bypassed certain components to hold the H/L doors closed because of another issue that will not allow them to close.
Sincerely
Bill