Under dash A/C blower motor added a relay - Chevelle Tech
Electrical & Wiring Troubleshooting electrical problems.

 
LinkBack Thread Tools Search this Thread Display Modes
post #1 of 10 (permalink) Old May 2nd, 14, 8:57 PM Thread Starter
JKK
Tech Team
JK
 
Join Date: Jan 2014
Location: Texas
Posts: 797
Under dash A/C blower motor added a relay

My under dash A/C blower motor was only getting 11.2 volts installed a relay with power coming from the horn relay now getting 12.8 volts blows twice as hard on high as it did before
JKK is offline  
Sponsored Links
Advertisement
 
post #2 of 10 (permalink) Old May 2nd, 14, 10:00 PM
Gold Member
Joe
 
Join Date: Aug 1998
Location: Lincoln, NE
Posts: 4,477
Re: Under dash A/C blower motor added a relay

Under-dash A/C blower?

Is this an aftermarket set-up?

-If you don't stand for something, you'll fall for anything.
Coppertop is offline  
post #3 of 10 (permalink) Old May 3rd, 14, 3:35 AM Thread Starter
JKK
Tech Team
JK
 
Join Date: Jan 2014
Location: Texas
Posts: 797
Re: Under dash A/C blower motor added a relay

Yeah it's a Vintage Air system
JKK is offline  
 
post #4 of 10 (permalink) Old May 3rd, 14, 7:25 AM
Tech Team
Dennis
 
Join Date: May 2013
Location: Illinois
Posts: 74
Re: Under dash A/C blower motor added a relay

Can anyone explain to me like I am 5, Why this works this way ?
Deisel23 is offline  
post #5 of 10 (permalink) Old May 3rd, 14, 9:24 AM
Lifetime Premium Member
Bob
 
Join Date: Mar 2005
Location: Jeannette Pa. near pittsburgh
Posts: 8,419
Re: Under dash A/C blower motor added a relay

Same process at having VERY bright headlights. My 70 Wagon and most all other Chevelles have, Not so bright headlights and dash lights.
Using relays, The headlights on my 70 are now 30-40% brighter and I now use the dimmer switch on the dash lights.
To take advantage of a 12 volt Batt. Make sure your, Lights, and all Accs. are getting 12 volts, 9-10-11 volts will make it operate, BUT not as good as 12 Vts.
Could that be the reason ALL modern cars/trucks use " RELAYS " ?????
Bob


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
1970 SS LS-5/M-22 El Camino- Org. Owner-AACA 2016-Senior Grand National Winner---MCACN-GOLD-2013
1970 ( FRAUD) SS 468 Station Wagon - Driver.
Robinls5 is offline  
post #6 of 10 (permalink) Old May 3rd, 14, 6:29 PM
Gold Member
Joe
 
Join Date: Aug 1998
Location: Lincoln, NE
Posts: 4,477
Re: Under dash A/C blower motor added a relay

The problem is, most people end up using relays as a 'crutch'. Instead of solving why there is a low voltage situation.

For example, 12.8 volts at the horn relay with the engine running is too low and indicates there are wiring/charging issues.

Bob--

The reason modern vehicles use so many relays is the controls on virtually item is dictated by the BCM, PCM etc. These modules are only capable on sinking or sourcing (providing a ground or positive out) a small amount of current that could not "drive" things like lamps, starter solenoids, fans, etc. They can however, drive relay coils directly, and of course the relays do the "heavy lifting" to provide the large current paths to the vehicle devices.

-If you don't stand for something, you'll fall for anything.
Coppertop is offline  
post #7 of 10 (permalink) Old May 5th, 14, 1:34 PM
Tech Team
Dennis
 
Join Date: May 2013
Location: Illinois
Posts: 74
Re: Under dash A/C blower motor added a relay

Quote:
Originally Posted by Coppertop View Post
The problem is, most people end up using relays as a 'crutch'. Instead of solving why there is a low voltage situation.

For example, 12.8 volts at the horn relay with the engine running is too low and indicates there are wiring/charging issues.

Bob--

The reason modern vehicles use so many relays is the controls on virtually item is dictated by the BCM, PCM etc. These modules are only capable on sinking or sourcing (providing a ground or positive out) a small amount of current that could not "drive" things like lamps, starter solenoids, fans, etc. They can however, drive relay coils directly, and of course the relays do the "heavy lifting" to provide the large current paths to the vehicle devices.

So, through a relay it takes less amount of current to drive say a headlight, than if it were wired directly without a relay ? Is that it ?
Deisel23 is offline  
post #8 of 10 (permalink) Old May 5th, 14, 7:56 PM
Gold Member
Joe
 
Join Date: Aug 1998
Location: Lincoln, NE
Posts: 4,477
Re: Under dash A/C blower motor added a relay

Quote:
Originally Posted by Deisel23 View Post
So, through a relay it takes less amount of current to drive say a headlight, than if it were wired directly without a relay ? Is that it ?

Dennis,

A relay is basically an electric switch. Contacts inside are operated by an electromagnet. The coil of wire inside a relay doesn't draw very much current at all. What ever your are controlling (fan, headlights, etc) still draw the same amount of current, the relay just takes the "burden" off a control switch or circuit.

Think of it like this, you could use a tiny toggle switch to turn on your headlights. If you tried to run the headlights directly thru the tiny toggle, it would quickly burn-up due to all the current the headlamps are pulling. By simply using the toggle to trigger a relay coil, the tiny amount of current for the coil is no problem for the toggle. In turn, the relay's contacts control the high current to actually feed the headlamps.

You would also need to run a new circuit or modify an existing one (the main power feed) to supply the relay's contacts and ultimately to the headlamps.

-If you don't stand for something, you'll fall for anything.
Coppertop is offline  
post #9 of 10 (permalink) Old May 6th, 14, 7:42 AM
Tech Team
Dennis
 
Join Date: May 2013
Location: Illinois
Posts: 74
Re: Under dash A/C blower motor added a relay

Quote:
Originally Posted by Coppertop View Post
Dennis,

A relay is basically an electric switch. Contacts inside are operated by an electromagnet. The coil of wire inside a relay doesn't draw very much current at all. What ever your are controlling (fan, headlights, etc) still draw the same amount of current, the relay just takes the "burden" off a control switch or circuit.

Think of it like this, you could use a tiny toggle switch to turn on your headlights. If you tried to run the headlights directly thru the tiny toggle, it would quickly burn-up due to all the current the headlamps are pulling. By simply using the toggle to trigger a relay coil, the tiny amount of current for the coil is no problem for the toggle. In turn, the relay's contacts control the high current to actually feed the headlamps.

You would also need to run a new circuit or modify an existing one (the main power feed) to supply the relay's contacts and ultimately to the headlamps.
Thanks for the info. I have to be honest, I understand that it's a remote switch...I just don't know the difference between that relay, and the headlight switch. I don't get how that benefits the system. And I don't think I need to at this point, I just need to accept that it does, and wire my stuff accordingly.
Deisel23 is offline  
post #10 of 10 (permalink) Old May 6th, 14, 7:34 PM
Gold Member
Joe
 
Join Date: Aug 1998
Location: Lincoln, NE
Posts: 4,477
Re: Under dash A/C blower motor added a relay

Dennis, the headlamp switch and a relay perform the same task--complete a higher current circuit. By using the relay (and new related wiring to connect everything) you take the burden off of the main power wire in the dash that used to provide all the current to the lights in addition to all of the dash controls and the rest of the car.

It's not just the relay, it's the relay being used to control a new circuit dedicated to whatever load you desire so the burden is taken off of the original circuit.

-If you don't stand for something, you'll fall for anything.
Coppertop is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Chevelle Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address. Note, you will be sent a confirmation request to this address.

Email Address:
OR

Log-in









Old Thread Warning
This Thread is more than 1966 days old. It is very likely that it does not need any further discussion and thus bumping it serves no purpose.
If you still feel it is necessary to make a new reply, you can still do so though.

Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may 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 Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome