Heater Blower Switch Question
Thread Starter
|
Senior User
Joined: Feb 2004
Posts: 220
Likes: 1
From: Castalia, Ohio
Heater Blower Switch Question
Hey friends!
Been forever since I've been here! Sorry for not being here in so long!
Well, here's my issue. My 78 F-350 heater blower switch in the dash only works in low. It used to work in all 4 speeds (low, med low, med hi, and hi) if I played with it, but now it only works on low. So I went to Autozone and Advance Auto Parts and both of them have a switch, but it has a completely different wiring plug in than the one I have. I think the one they carry is the one that has an "OFF" position, whereas mine does not. Mine only goes to low. I also went to the dealer whom told me they only go back to 1980 in the computer and everything prior to that is on microfilm. And of course they do not have a microfilm reader!
So, does anyone have a part number for this item or an idea who might carry one? My truck has A/C if it makes a difference. Thanks all!
Been forever since I've been here! Sorry for not being here in so long!
Well, here's my issue. My 78 F-350 heater blower switch in the dash only works in low. It used to work in all 4 speeds (low, med low, med hi, and hi) if I played with it, but now it only works on low. So I went to Autozone and Advance Auto Parts and both of them have a switch, but it has a completely different wiring plug in than the one I have. I think the one they carry is the one that has an "OFF" position, whereas mine does not. Mine only goes to low. I also went to the dealer whom told me they only go back to 1980 in the computer and everything prior to that is on microfilm. And of course they do not have a microfilm reader!
So, does anyone have a part number for this item or an idea who might carry one? My truck has A/C if it makes a difference. Thanks all!
Laughing Gas
Joined: Sep 2004
Posts: 1,169
Likes: 4
From: Whitby, Ontario, Canada
You might find it with NPD or Dennis Carpenter. I bought the entire heater/Ac control assemble on ebay for $15. It was from a '78 and the switch was differnt than my '76. Since my switch was shot and the '78 looked like a better design, I spliced the wires and connected it, the colour codes were identical.
Post Fiend
Joined: Jul 2003
Posts: 11,945
Likes: 3
From: Spokane, WA
I could be wrong here but I don't believe the problem is your switch. If you follow the wires from the switch they should go to a little box on the body of the heater housing. It will be a 3 prong plug if I remember correctly. This is a very simple resistor (?) setup with 3 coils that control the power to the fan. I think it's most likely that this is the culprit rather than the switch but I could be wrong on this. Hopefully someone else can give an opinion here.
Postmaster
Joined: Apr 2000
Posts: 2,881
Likes: 1
From: North of Tulsa, Oklahoma
That switch should work just fine if your wiring plug fits it. I replaced the switch in my 78 F150 w/ factory air and now instead of three settings(low,med,high) I've now got four settings(off,low,med,high). There's nothing wrong with using the four setting switch. I replaced mine because it had substantial internal rust and eventually gave out. It wouldn't hurt to take a look at the thermostatic coils, but my 27 year old coils are in pristeen condition. My heater blower motor was the second culprit. The poor thing had finally given up the ghost and wouldn't spin freely anymore. A new blower motor brought my system back to life. You could try disconnecting the blower motor quick connect plug and temporarily hook up +12VDC to it to see if it still spins freely. Good luck.
Freshman User
Joined: Nov 2004
Posts: 43
Likes: 1
ivanribic is on the right track. My blower motor resistor went out and the fan only worked on one speed. In my 77 (with A/C), its mounted on the bottom of the dash under the glove box. Be carefull whom you buy it from, I got my first one from Autozone and it was a piece of junk. The fan wouldn't turn off even with the key off!! I bought the next one from Carquest and it works fine. Good luck and I hope this helps.
Senior User
Joined: Apr 2005
Posts: 446
Likes: 1
From: South Bend, IN
Actually the only time the resistor is in the circuit is on the lower two speeds. Full battery voltage to the fan motor gives you the highest speed. If it won't work on high then it almost has to be the switch or wiring to it. Usual symptom of a resistor problem is a fan that works OK on high but not on medium or low.
Thread Starter
|
Senior User
Joined: Feb 2004
Posts: 220
Likes: 1
From: Castalia, Ohio
Thanks for all the replies everyone! I plan on checking it out further on Sunday and I'll let you know.
Trending Topics
Fleet Owner
Joined: Jan 2004
Posts: 26,007
Likes: 575
From: Brentwood,CA
the switches are the same for all of the them they all have the same part number. in a factory a/c setup the switch is not fully off unless the the slide lever is moved from a vent position to off the slide lever has contacts on the back which break apart when in the off posistion and remain closed when in any other posistion so the lowest you can go is low unless it is slid over to off. then the switch no longer has power.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
More Turbo
Joined: Mar 2002
Posts: 606
Likes: 3
From: Colstrip, MT
The blower motor switches were changed during the '78 model year. If you have a truck with the serial number ending in CA0001 or greater, it will use the newer style switch. If the serial number is prior to CA0001, then the old style switch is used. The ford dealer still has the old style switch, but he will have to drag out the microfiche to find the number. It cost about 12 dollars. If you just ask for a blower switch for a '78 ford, they will always give you the newer switch, because that is the one listed in their computer.
I can locate a part number tomorrow. I am at work right now and don't have access to the info.
I can locate a part number tomorrow. I am at work right now and don't have access to the info.
Last edited by fatherdoug; Sep 11, 2005 at 12:04 AM.
More Turbo
Joined: Mar 2002
Posts: 606
Likes: 3
From: Colstrip, MT
The old style switch is Ford part # D3AZ-19986-A.(prior to serial # CA 0001)
The new style switch is Ford part # D5AZ-19986-A.
These are for units that have factory A/C. The number MAY be different for aftermarket or dealer installed units.
The new style switch is Ford part # D5AZ-19986-A.
These are for units that have factory A/C. The number MAY be different for aftermarket or dealer installed units.
Elder User
Joined: Dec 2004
Posts: 769
Likes: 0
From: Idaho cda postfalls
heater
im still going with ivan on this one. i would check that resistor since it takes about two seconds to rmove it from the heater. does it only work on high if it is the resistor it will only work on high.
Last edited by fordfury469; Sep 13, 2005 at 02:03 PM. Reason: i was wrong maybe
Thread
Thread Starter
Forum
Replies
Last Post
We_Mud_Boggin
1999 - 2003 7.3L Power Stroke Diesel
2
Sep 14, 2011 08:53 PM
Dualiedo
Cooling, Heating, Ventilation & A/C
4
Sep 25, 2002 09:21 PM
