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It's going to be 100 degrees time to fix the heater


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3 minutes ago, SydneyTii said:

Check power to the fan motor, try spinning the blade, see if it’s free, check the fuse.

it’s not the worse job to pull the box, but more difficult on earlier cars I believe due to the flap controls.

 

Thanks should have mentioned its a 1974 base model.

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Ok bit easier then , if you take the box out, block off the 2 outlets as water remains in the heater rad and can make a mess as you rotate the box, I used a bit of hose, but if you can get caps they work just as well.

F896C9F6-73AC-4BA4-9332-2C21A8BE17B0.jpeg

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If the fan blade spins, then check the connection on the resistor board for the Green/brown and Red wires.

This terminal tends to fail for some reason...high current, heat, etc.

If the terminal is good (or fixed), then apply +12V to the Green/brown wire and ground the Brown wire.

Fan should operate at high speed. Then you can check the resistors on the board.

See below for resistor values.

 

Blower Motor Scan.jpg

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6 hours ago, John76 said:

If the fan blade spins, then check the connection on the resistor board for the Green/brown and Red wires.

This terminal tends to fail for some reason...high current, heat, etc.

If the terminal is good (or fixed), then apply +12V to the Green/brown wire and ground the Brown wire.

Fan should operate at high speed. Then you can check the resistors on the board.

See below for resistor values.

 

Blower Motor Scan.jpg

 

 

thanks ever so much I have not been able to work on the heater because the battery died on my car but I bought a new one today.

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The earlier cars have a different way of disconnecting the Bowen cable from the box than do the later cars (I think).

on the later cars you just pop off the lever cap ends and chrome faceplate and take out the screws then push the whole thing backwards, I believe the earlier cars need to have the cables removed differently.

There was a post on this recently, have a search it should come up, someone with an earlier car will probably respond.

Just found this one, older but relevant, it says on early cars it's either a dash out job or slip the cables off the levers.

if your car is later just take off the lever ends and pop off the chrome plate you will see the screws

 

 

Edited by SydneyTii
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9 hours ago, John76 said:

If the fan blade spins, then check the connection on the resistor board for the Green/brown and Red wires.

This terminal tends to fail for some reason...high current, heat, etc.

If the terminal is good (or fixed), then apply +12V to the Green/brown wire and ground the Brown wire.

Fan should operate at high speed. Then you can check the resistors on the board.

See below for resistor values.

 

Blower Motor Scan.jpg

I find these (what I call to myself "Dr. Suess" wiring diagrams) eminently understandable - I think you could bundle them into a book. 

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5 hours ago, Eissmann said:

Your subject line caught my attention because mine is always blowing hot air. 

Eissmann,

Does your fan motor work?

If so, and it's always blowing hot air, even with the fan off, then it is a control valve problem.

No need to take the whole enchilada out of the dash...just check the valve operation with a garden hose.

The valve has a small hole (even when closed) that allows a small amount of coolant to circulate through the heating coil. This is to prevent air pockets and keep the coolant from becoming stagnant during the summer months. As a result, you always get a small amount of heat through the vents. If the vent air is very warm, even when the lever is in the "Cold" position, then check the adjustment of the cable to the valve. The levers on the left side of the steering wheel control the flaps for selecting defrost and/or vent air.

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I should have said when I am driving, hot air is coming out of the heater vents. My fan motor seems to work fine. I have seen a repair kit for the valve and assumed that might be the cure.  (I have a 76 if that makes any difference)

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I would start with removing the valve and cleaning and testing it for correct operation. You will likely find gunk in the valve seat that prevents it from closing fully. Or, in my case, a broken shaft on the ball valve. I repaired mine with JB Weld and it has worked perfectly for the last 4 years.  Be sure to assemble the valve correctly. It has a spring retainer for the ball valve that allows the ball to seat fully when the coolant is flowing in the right direction (see the arrow on the valve). However it does not hold pressure in the opposite flow direction! If the valve has been "serviced" in the past, it may be assembled backwards, which will allow lots of coolant to always flow through the heating coil.

Hopefully this is an easy fix. Wait until winter to take the entire assembly out for a complete overhaul.

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