Go Back   Ford Truck Enthusiasts Forums > Older, Classic & Antique Trucks > 1973 - 1979 F-100 & Larger F-Series Trucks
Sign in using an external account
Register Forgot Password?


1973 - 1979 F-100 & Larger F-Series Trucks Discuss the Dentsides Ford Truck

Reply
 
 
 
 
LinkBack Thread Tools Search this Thread
  #1  
Old 10-12-2014, 09:08 PM
Haydendh Haydendh is offline
Freshman User
 
Join Date: Sep 2014
Posts: 32
Haydendh is starting off with a positive reputation.
Need electrical a/c help on 77 F150

I decided to replace the blower motor on my truck because nothing happens when I turn on the fan. After I took off the vent cover that exposes the evaporater and condenser I noticed the blower motor plug was melted some. So I decided to stop right there and see if I had power to the plug and nothing. Next I went to the resistor. There was no power to either one of the plugs on the resistor. Next I went to the relay , the relay has power on one of the prongs. So I thought maybe it was the relay, replaced it with a part number I found on another thread from oreillys and still no power at the resistor. Can someone tell me what the chain of power is on this whole process. Which plug is suppose to have power on the resistor and where does the relay come in to play? Thank you
Reply With Quote
  #2  
Old 10-12-2014, 10:11 PM
mikeo0o0o0's Avatar
mikeo0o0o0 mikeo0o0o0 is offline
Post Fiend
 
Join Date: Apr 2009
Location: Davenport, Fl
Posts: 10,146
mikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to behold
Go here:
http://www.ford-trucks.com/forums/13...then-some.html
And here:
1973-1979 Ford Truck Wiring Diagrams & Schematics - FORDification.net
If you go to Fordification, you can use the '76 wiring schematics. The A/C wiring is the same as your '77.
Reply With Quote
  #3  
Old 10-12-2014, 10:19 PM
Haydendh Haydendh is offline
Freshman User
 
Join Date: Sep 2014
Posts: 32
Haydendh is starting off with a positive reputation.
I looked at all those before but they don't tell what feeds what. I know how it all hooks up just not sure what is suppose to be hot and so forth. Thank you though
Reply With Quote
  #4  
Old 10-12-2014, 10:33 PM
Haydendh Haydendh is offline
Freshman User
 
Join Date: Sep 2014
Posts: 32
Haydendh is starting off with a positive reputation.
Quote:
Originally Posted by Haydendh View Post
I looked at all those before but they don't tell what feeds what. I know how it all hooks up just not sure what is suppose to be hot and so forth. Thank you though
Let me rephrase that, I think that one schematic may show what feeds what but I can't understand it lol.
Reply With Quote
  #5  
Old 10-12-2014, 10:54 PM
mikeo0o0o0's Avatar
mikeo0o0o0 mikeo0o0o0 is offline
Post Fiend
 
Join Date: Apr 2009
Location: Davenport, Fl
Posts: 10,146
mikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to behold
Okay, go to page 4 of the '76 wiring diagram, upper left you'll see the A/C circuits. Look at the "safety relay", that's what Ford calls it. Everyone else calls it the blower relay.
The wire that you showed was hot should be the orange one. The one that controls whether this relay turns on or not is the yellow w/ red trace wire, circuit #753. With the A/C on check whether you have voltage at the relay plug. If you don't show any voltage, go to the A/C mode switch (on the A/C control panel) and check for voltage at the orange wire, circuit #181. If you show voltage there you need to replace the switch, this is part of the vacuum control switch and isn't available separately.
This is what the switch looks like.
Attached Images
 
Reply With Quote
  #6  
Old 10-12-2014, 11:32 PM
77&79F250's Avatar
77&79F250 77&79F250 is offline
Workaholic
 
Join Date: Feb 2007
Location: S/W Missouri
Posts: 16,399
77&79F250 has much to be proud of77&79F250 has much to be proud of77&79F250 has much to be proud of77&79F250 has much to be proud of77&79F250 has much to be proud of77&79F250 has much to be proud of77&79F250 has much to be proud of77&79F250 has much to be proud of77&79F250 has much to be proud of77&79F250 has much to be proud of
Here is some more a/c help.

1979 F100 Air Conditioning

NORTH COUNTRY SPECIALTIES ®
__________________
77&79 F250 Rich & Penny
77 351M auto, a/c, add a leaf 33x12.50's
78 (79 headlights) 460 4 spd, 4", a/c and 35's
79 351M 4spd 6" Skyjacker Edelbrock-Holley-Hedman 35's
99 Ranger 4x4, 98 Expedition 4x4, 73 Bronco Hillbilly-Bug
71 Bronco 302 35" Boggers 5.58 gears spool/locker
Reply With Quote
  #7  
Old 10-13-2014, 01:20 AM
Haydendh Haydendh is offline
Freshman User
 
Join Date: Sep 2014
Posts: 32
Haydendh is starting off with a positive reputation.
Would you have the part number I can't make out the one on the box. Thank you
Reply With Quote
  #8  
Old 10-13-2014, 02:16 PM
Haydendh Haydendh is offline
Freshman User
 
Join Date: Sep 2014
Posts: 32
Haydendh is starting off with a positive reputation.
Ok I have power at the yellow wire on the relay, but that's it. The power goes off when I turn the ac off. You can hear the relay click when I turn it on and off so I think it's good, plus it's brand new.
Reply With Quote
  #9  
Old 10-13-2014, 02:55 PM
Haydendh Haydendh is offline
Freshman User
 
Join Date: Sep 2014
Posts: 32
Haydendh is starting off with a positive reputation.
Update

I checked the vaccum control switch and it seems to be working properly. Does anyone know what all wires should hAve power going in to the relay?
Reply With Quote
  #10  
Old 10-13-2014, 07:02 PM
Haydendh Haydendh is offline
Freshman User
 
Join Date: Sep 2014
Posts: 32
Haydendh is starting off with a positive reputation.
Boom !! Finally figured it out the orange wire ran to the starter relay ( which the previous owner just replaced) and he had it on he negative side. So after buying a new blower motor, relay, and heater core it was just a crossed wire lol. Thanks everyone for the help.
Reply With Quote
  #11  
Old 10-13-2014, 07:14 PM
mikeo0o0o0's Avatar
mikeo0o0o0 mikeo0o0o0 is offline
Post Fiend
 
Join Date: Apr 2009
Location: Davenport, Fl
Posts: 10,146
mikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to beholdmikeo0o0o0 is a splendid one to behold
Quote:
Originally Posted by Haydendh View Post
Boom !! Finally figured it out the orange wire ran to the starter relay ( which the previous owner just replaced) and he had it on he negative side. So after buying a new blower motor, relay, and heater core it was just a crossed wire lol. Thanks everyone for the help.
Glad you found it .
Quite often the worst thing that can happen to one of our trucks is a "previous owner".
Reply With Quote
Old 10-13-2014, 07:14 PM
 
 
 
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
1983 E250 Club Wagon 6.9L Diesel Blower Motor issues! LeeTribeRide 1968-2013 Full Size Vans 3 11-09-2013 05:10 PM
1983 E250 Club Wagon 6.9L Diesel Blower Motor issues! LeeTribeRide Cooling, Heating, Ventilation & A/C 0 11-09-2013 01:46 PM
99 Exped Front Blower Problem wmingari Expedition & Navigator 13 07-13-2013 02:03 PM
1997 ford ranger heater motor issue oddone1975 Ranger & B-Series 42 04-13-2013 08:27 AM
Fan Blower Relay chuckers98 Electrical Systems/Wiring 13 02-14-2010 11:50 PM


Go Back   Ford Truck Enthusiasts Forums > Older, Classic & Antique Trucks > 1973 - 1979 F-100 & Larger F-Series Trucks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

Forum Jump


Participate In The Forums

Create new posts and participate in discussions. It's free!

Sign Up »





All times are GMT -5. The time now is 03:10 AM.


Powered by vBulletin® Version 3.8.7 AC1
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Advertising - Terms of Use - Privacy Statement - Jobs
This forum is owned and operated by Internet Brands, Inc., a Delaware corporation. It is not authorized or endorsed by the Ford Motor Company and is not affiliated with the Ford Motor Company or its related companies in any way. Ford® is a registered trademark of the Ford Motor Company.

vbulletin Admin Backup