Mercury Marauder

1969 Mercury Marauder Heating / Cooling System Malfunction Happens always Always

The Blower fan and the A/C clutch both deactivate at the same time. The A/C will blow very cold air but after running for about ten minutes, both the fan and the A/C shut-off. If I turn the blower fan off for about a minute, the A/C will blow cold again and then repeat the same process. I don't have to restart the A/C, the clutch reengages after I turn the blower fan back on.

Hello, Wiring diagrams are hard to come by. Still, I have a suggestion.

1. Look at the fuse that is for the A/C system. Does it show signs of overheating?
2. Look at the wiring connector for the power wire to the blower motor. Does it show signs of overheating?
3. Look at the connector to the blower fan speed control switch. Does it show signs of overheating?

If a blower motor has been in service for a long time it gets harder to turn. This would call for more amps to run the motor. Usually the result is a connector or fuse holder will heat up and even melt in worst cases I've seen.

When the blower has been running for one minute and with the car's engine running the amp draw called for by the blower motor needs to be checked. If the amp draw exceeds the rating of the fuse for the blower motor heat will begin to build. That is not a short circuit so the fuse doesn't blow. But connectors and fuse holders will heat up until there is so much resistance the power no longer gets through the circuit.

When you shut the fan off the wiring for the blower cools down and the power can once again get through the circuit until the heat builds up again. This will keep up until the fuse finally pops or there is an electrical burn of the wiring or connectors in the circuit.

Take your time and take a good look. Your classic car needs some help.

Roger

On inspection the fuses don't appear to have any damage. I will check again. I will also have to educate myself on checking the amperage. Will get back to you. Do you suggest replacing the blower fan motor? Is it an expensive procedure? I also checked the fan running by itself without the A/C on, it appears that no air comes from the dash level but air does blow at windshield level, I guess that's the defroster. Is that normal?

The airflow should deliver where you have selected it regardless of air temperature or compressor operation. If you select defrost, vent, heat, if it is a manual hvac system.

Replacing the blower motor might fix things but one shouldn't ignore inspecting for heat damage to the circuit and it's components and connectors. The car is old enough that the possibility is likely.

It is a fairly easy task to replace the blower motor. You may wish to shop different auto parts stores for the best price and warranty.

You may well find information/instructions at your public library.

An inductance amp probe and the multi-meter to read it are expensive tools. You may want to seek the help of a good shop that has them.

Roger

Thanks for the help! It's too late to get back to you with reponses to your previous suggestions but I can see from your responses thAT this is an excellent website. Is it ok to complete this later on the same dime?

Yes, take the time you need. This is not a live chat and holding the question open for a few days is common and normal as you need time to apply the ideas offered to resolve the problem.

Thank you for the positive comments. I'm only one of many providers that answer questions and I hope you will be pleased with what you find here. I will not be paid until you accept my answer as the help you needed. Working on the same dime applies so long as work concerns the original question.

Thanks,

Roger