heater motor

[jakerboy]

Hello
I was wondering where i could get a heater fan switch .Could i just use a universal 3 speed switch from napa or somewhere else ?Or should i try to find a factory replacement one . Should i put it on a relay ? Thanks again for the help.

[Megunticook]

I got an aftermarket switch from NAPA (Echlin #ECHHC203) that is basically just like the factory unit and is a snap to install.

http://www.napaonline.com/MasterPages/NOLMaster.aspx?PageId=470&LineCode=ECH&PartNumber=HC203&Description=A%2fC+%26+Heater+Blower+Motor+Switch

It's a little pricey ($22), I'd check rockauto.com for the Standard Motor Products version (pretty sure they have one).

Wiring's pretty straightforward, give a shout if you have any questions.

If you want to save a few bucks you could also use a 3-position generic switch (that's what the previous owner had installed in my truck), just make sure the amperage rating is sufficient for the blower motor circuit (20A should do it).

[jakerboy]

Thanks Meg
Thats what i was looking for . Should i put it on a relay?

[77Utiline]

YES!!! Sorry for interrupting but definitely put it on a relay it will save you time, money, and pain relievers.

[Megunticook]

I didn't bother, but it certainly wouldn't hurt. I'm just in the middle of my first experience installing relays with my headlamps--pretty simple stuff.

For what it's worth, my local "crusty old mechanic" (as bherder likes to say) swears by Bosch relays only, says every other make he's tried ends up wearing out. Bosch was bought out by Tyco, so they might be sold under that name now.

Have at it!

[77Utiline]

At $22 a switch or even $6-7 (hardware store) by adding the relay (any generic will do) it saves money on switches and fewer fire extinguishers

[jakerboy]

Hello I seen some relays that came with a socket and a harness The wires are 16 gauge . Are they worth using ? Thanks

[77Utiline]

16 gauge would be more than enough

[L5wolvesf]

YES!!! Sorry for interrupting but definitely put it on a relay it will save you time, money, and pain relievers.

Does anyone have a wiring diagram for doing this?

Thanks,
L

[77Utiline]

I will try to find the web link, but if I remember correctly there was another post on DT on this subject.

[Chump]

See if this makes sense to you...it'e for a 77 heater only truck..if you have A/C just add another circuit like whats shown. :):)

[jakerboy]

Thanks Chump
So this is a picture with ac . I just need to take out the top relay circuit for heat only ? Thanks

[77Utiline]

No, actually this is a schematic for relays on both the high and the low sides of the blower switch.

[jakerboy]

Okay Thanks This relay wiring is all new to me . I will get right eventually . I see how the circuit works now . Thanks again

[77Utiline]

Even though I have had training as well as in shop experience the only reason I even have the slightest clue is because I am fabricating an entire wiring harness for my '77

[Chump]

Thanks Chump
So this is a picture with ac . I just need to take out the top relay circuit for heat only ? Thanks


This is for "HEAT" only trucks....just add another circuit for an "A/C" truck.
Heat only trucks have 2 speeds....Low and High
A/C trucks have 3 speeds....Low, Medium, High
There is another way to do this for A/C truck with just 2 relays but I havnt had time to persue the actual build up and test of the circuit.

Here's the story guys and gals. The resistor block lowers voltage to the blower motor to give you the slower speeds. It does this by changing electrical flow to heat, this heat is drawn off by the blower motor and the heater box. To get a slower(LOW) speed you must have higher resistance, this creates more heat. Unfortunately when the resistance is restricted the whole circuit takes a beating including the dash switch and wiring. Also you will note that when using Low speed you create more heat and the blower is turning slower and you have less air flow, so it's a vicious cycle!
It's best to use a GXL wire type if you want to rewire...this has a higher heat rating of 125*C. (TXL is thinner and SXL has thicker insulation but both have same heat rating of 125*C) Most of the stuff you get in the auto parts stores is GPT with a rating of 80*C.
Any questions...just ask.
Regards-Stevo

P.S. You might want to consider some sort of terminal/distribution block for under the dash. This would make power easier to access for any mods inside the cab. Be sure to mount it in a safe place. Feed it with at least a 10 or 8ga fused supply wire from under the hood. Fuse to be near the power source under the hood.

[jakerboy]

Thanks Chump
Heres what i am doing . Iam totally rebuilding a 73 w200 . I am building a custom dash for it . The truck is being rewired with a painless kit . I am going to put all of the switches on toggles and relays . Heres some questions ! Should the relays draw power from the battery or the alt ? Can i run a terminal distribution block close to the relays and power them from it ? Where should the relays be located? Is 16 ga wire okay to run to the switches. Where can i buy GXL wire and a distribution block like you picture ? The wire in your picture is fuse link ? I am trying to do this right the 1st time . Sorry for so many questions . Thank again for your help .

[L5wolvesf]

See if this makes sense to you...it'e for a 77 heater only truck..if you have A/C just add another circuit like whats shown. :):)

Once aqgain Chump is da man :)

Thanks,
L

[Chump]

Since I'm old and feeble, I'll break this down this way. :):)

Heres what i am doing . I am totally rebuilding a 73 w200 . I am building a custom dash for it . The truck is being rewired with a painless kit . I am going to put all of the switches on toggles and relays . Heres some questions !
Sounds cool!

Should the relays draw power from the battery or the alt ?
You can do either, or draw power off the starter relay battery connection on the inner fender. You will find most experts say to draw power off the alternator. I won't disagree but it depends on how you want to route your wires. Your truck with all new wiring should run sweet because of the low resistance in the new copper. I don't like any direct connections on the battery clamps themselves due to corrosion. The alternator and the starter relay are not as prone to this problem. Example...Also remember if you run 12ga(or whatever gauge)power wire to a device that you must also have 12ga(or whatever gauge) wire for the ground on that device. If you run a smaller gauge ground wire then you have just created a resistance point and poor circuit performance.

Can i run a terminal distribution block close to the relays and power them from it ?
Sure, just take into consideration your wire gauge and length from the power source. Also don't forget fuses or circuit breakers in your circuits close to the power source as possible.

Where should the relays be located?
It would be best to keep your power supply FROM the relays to the device as short as possible...but this is not a reason to place relays in a spot you don't want them. Make it appealing to you!

Is 16 ga wire okay to run to the switches?
Yes, as long as these the switches are used to activate(pick) the relays. They require almost no current to pick. Never run high current circuits thru a switch unless the switch is designed for that purpose. The contacts inside will fry. This is why we use relays...the relay is actually just a HD remote switch.

Where can i buy GXL wire and a distribution block like you picture ?
The block is from www.madelectrical.com get the tech book too if you order from him. He's good people. For the GXL wire, if you only need small lengths you can go here www.kayjayco.com but it's more expensive then buying the 100' rolls from a place like www.terminalsupplyco.com Do some pricing.

The wire in your picture is fuse link ?
Yes, that's just a picture from another website showing how to fix multiple fusible link wire problems on the later trucks from the 80's on up. the block can be used for any type wires.

I am trying to do this right the 1st time . Sorry for so many questions . Thank again for your help .
If you never ask any questions...you'll never learn. :):)

[jakerboy]

Thanks a million Chump . Your help is greatly appreciated This will help speed up my wiring project .I am petty sure i have a handle on it now . Thanks man.
Should the GXL wire be used to send power to the relays ?

[L5wolvesf]

See if this makes sense to you...it'e for a 77 heater only truck..if you have A/C just add another circuit like whats shown. :):)

A couple questions:
- My fuse connections for the heater melted should I just run an inline fuse?
On the diagram, does the fuse between power & relay do the same as the original fuse? FYI - I did have A/C

- What is "Dash" on the diagram a ground?

Thanks,
L

[Chump]

Thanks a million Chump . Your help is greatly appreciated This will help speed up my wiring project .I am petty sure i have a handle on it now . Thanks man.
Should the GXL wire be used to send power to the relays ?

Use the GXL under the hood for sure. You can get away with using the GPT under the dash but the GXL is much better all around as the wire strands are configured a bit different also.

[Chump]

A couple questions:
- My fuse connections for the heater melted should I just run an inline fuse?
On the diagram, does the fuse between power & relay do the same as the original fuse? FYI - I did have A/C

- What is "Dash" on the diagram a ground?

Thanks,
L

You can run an inline fuse or try to repair the original fuse holder in the fuse box itself. I have not had time to find a suitable fuse holder that could be epoxied into the old fuse box but I have repaired several loose ones with epoxy.
http://www.autorewire.com/tech/article/loosefuses.html

The fuse on the diagram does the nearly same thing as the fuse in the fuse box but you need power to the dash switch so the original fuse must be in working order.

A/C...just means another circuit for the Medium speed blower setting and is kinda up to you if you still want to keep that setting. Low and High will work for most people.

DASH=Dashboard side of the firewall. The power wire for the blower runs thru the firewall on this diagram.