dannyda

1990 Mrecury Grand Marquis:

Still after a year and a half, I am unable to get my heating system working properly. Today I did find out that I get plenty of air through the heating system if I start the car and leave it in park, but as soon as I put it in gear
I loose the air coming into the car. I checked the blower motor voltage after this and I am still getting 14 volts when blower is on high and the engine running. But air coming in is like on low setting. Anybody have any idea what to look at next. Why would putting car in gear affect the heating system?Considering getting rid of this car and finding another project that is hopefully not so frustrating. Like the car but can't drive it in the winter with no heat. And the wife is getting upset with the money I have already invested in it.

Thanks for any and all suggestions, Dan

Bert

Does it sound like the blower motor slows down or a restriction comes into play?

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Bert

dannyda

Sounds like motor has slowed down, that is why I checked to see if any volatge drop, voltage was still at 14. Some reason I'm thinking a vacume problem. Not sure if I should replace MAP or not, checked for vacume leaks already and did not find any.

Bert

Try unhooking the vacuum to the heater system and see if it seems the same as when you first run it.

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Bert

dannyda

do you mean the hose that goes throught the firewall to the inside controls?

Bert

Yes, that way it will tell wether it's the flaps or the motor.

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Bert

dannyda

Bert, Thank you.

We have a winner, I now have at least air coming into the car at all times. Should be more but it is better then before. I have to assume that now I have to find out which actuator is the problem or if it is the little vacume disk under the dash. I can change where the air comes out with no problems, just not geting as much out as there should be. What do you think Bert? And agian Thank You. Never thought about disconnecting hose to isolate the problem.

Bert

The best way would be to use a vacuum pump and check each circuit. There's a reservoir under the hood that can leak too. There's also a check valve. I don't have access to the vacuum circuit or I could help a little further. If I'm looking at the system, I can usually find where all the circuits are and check them. Glad you're getting somewhere with it. Maybe a Haynes or Chilton manual would help. Check your local library.

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Bert

dannyda

Bert: Am I thinking wronge on my last post by wanting to look under the dash. Had all last night while at work to think about this and think I should be looking under the hood now instead. Here is what I have.

Prior to unhooking vacume hose, with the selector on vent and the blower motor speed on high, I would feel air coming from the vents at the steering wheel, but then after putting car in gear the air would stop coming out.

After unhooking hose I now feel air at the steering wheel all the time, it is now atleast consistant, still should be blowing out past the steering wheel.

Thanks again, Dan

Bert

A vacuum leak can be under the dash or under the hood. The control switch can also leak. I wish I had a diagram, it would help a lot. Do you have a Haynes or Chilton manual?

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Bert