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heater

I have a 1973 F150 and am having trouble with my heater. I am pretty sure that the fan or blower is the main problem and not the heater core itself. At times the blower will start and then stop. At this point I am thinking that either the switch is bad or there is a loose wire somewhere. I would like to have some information on how to trouble shoot the switch and or wiring. Also can anyone tell me where exactly the blower is and the best way to get to it.

Thank You
Larry
 

fatherdoug

Tonto Papadapolous
Welcome. You might try posting this in the Generation 6 Sub forum(1973-1979 Fords).

Listed below is a link to the 1978 service manual, which is very similar to the 1973. How you access/replace the blower motor/heat exchanger will depend on whether or not the truck has A/C, and whether or not the A/C is factory installed or dealer installed. There have been some write-ups on replacing the heater core/blower motor if the you search the Gen 6 forum. Good luck.

http://www.fordtruckfanatics.com/forum/showthread.php?t=31386
 

fatherdoug

Tonto Papadapolous
I had a similar situation. Hitting bumps in the road would cause the blower motor to come on / go off. A blower motor replacement solved the issue.

As Frank asked, if the heater only works on the high position, then the resistor is bad and needs replaced. This is a relatively painless replacement.
 
I had a similar situation. Hitting bumps in the road would cause the blower motor to come on / go off. A blower motor replacement solved the issue.

As Frank asked, if the heater only works on the high position, then the resistor is bad and needs replaced. This is a relatively painless replacement.

Is there a simple way to check to make sure the blower is the issue. Diagram would help along with written insturctions.

Thank you
Larry
 

fatherdoug

Tonto Papadapolous
Here is a write up done by UTFBALL.(Thanks, Ben) There is also a step by step provided in the service manual link above that I posted. Again, whether or not you have A/C, factory or dealer, makes a difference. If you can get to the connector to the blower motor and separate it, and put the blower on high, you should have 12 volts at the connector.

It's not too bad. Never done it on a 73, but I'll assume it's somewhat similar to the 77-79's. Attack it from under the dash/glove box area. These steps I think I got from Dennis, and used them the first couple times I replaced A/C cores.

1. Disconnect the battery ground cable.
2. Remove the air cleaner.
3. Drain the engine coolant below the level of the heater core.
4. Remove the heater hoses from the heater core.
5. Remove the screw fastening the A/C hose support bracket to the firewall.
6. The expansion valve is located on the right side of the evaporator core housing. Remove the insulating tape covering the valve.
7. Remove the two screws holding the plate over the opening that the A/C hoses exit the evaporator housing. Remove the plate and the seal.
8. Remove the glove box liner.
9. Separate the A/C duct from the register in the instrument panel and free the clip holding it to the plenum. Remove the duct from under the dash.
10. Remove the vacuum hose from the vacuum motor on the right hand side of the air box.
11. Remove the rear housing cover from the evaporator housing. The cover is retained by 4 nuts and one bolt. Disconnect the fresh air tube from the rear cover. After the cover is removed reinstall one nut to secure the evaporator housing to the firewall.
12. Gently remove the capillary tube from the evaporator core. Disconnect the wires from the icing sensor. Remove the plate the sensor is mounted to.
13. Remove the plenum by extracting the two screws above the transmission tunnel that hold the plenum to the dash.
14. Remove the screws securing the evaporator.
15. Pull the evaporator from the case and secure it above the case.
16. Remove the heater core.
17. Remove the heater air control door. There are no screws this is retained by a spring clip and snaps off.
18. Remove the arm that supports the air control door and the retainer that secures the pivot arm.
19. Remove the blower motor.
20. Transfer the blower wheel to the new motor.
21. Reverse the disassembly steps to assemble the heater A/C box

First time I did it, took me about 4 hours, now I can do it start to finish in about an hour and a half. The smaller you are, the quicker it'll go because of the tight quarters.
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Last edited:

BKW

Ford Parts Guru
With Fresh Air heater only, or does the truck also have A/C?
 

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