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DIY: Here's how to add a Relay to an electrical circuit
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badufay
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PostPosted: Thu Dec 22, 2011 12:12 pm    Post subject: DIY: Here's how to add a Relay to an electrical circuit Reply with quote

VW Beetles push a lot of power through the ignition switch. This part (IMHO) is the biggest contributor to voltage drop in VWs. Even with new wires, connectors and switches, these cars can easily exceed 3% in voltage drop (13.5 volts at batt w/ car running, then no electrical item should have less than 13.1 volts)
This is why I run relays on every major power consuming item in my car (wipers, headlights low & high, coil, rear defroster, and after market heater assist fans) ...here is a picture of your standard 12 volt relay setup you can buy at any auto parts store for around $6.

Image may have been reduced in size. Click image to view fullscreen.

Adding a relay simply uses the original power wire as a switch to the relay with minimal power required. I'm sure this will offend many because it didn't come stock, so feel free to call me "The P.O."
Besides improving the electrical systems overall performance and safety of your car, it can also help with engine performance gains (calm down, I'll explain). Again, voltage drop in these cars is going to happen...The (+) wire to the coil runs a long way before it actually reaches the coil, this added distance and things mentioned earlier can often times leave your coil 2 whole volts below the battery voltage. This alone will impact voltage to the spark plugs, thus reducing power and fuel economy. A full shot of power to the coil and from the coil will have your ignition system running like new, if not better. It has been my experience that voltage issues to the coil are the biggest problems with point replacement products like pertronix (that and being hooked up backwards). Pertronix states that when using their product, spark plug gaps can be increased by 0.005", which means you can gap your VW plugs (NGK B5HS) to about 0.030"! I know some will argue that its nothing but a points replacement part, I can tell you on my 1600 w/ a relayed Bosch Blue coil and pertronix, my car runs amazing with a gap of 0.030".
Feel free to disagree, but hopefully this can help some people out.
Below are some diagrams I made to show exactly what I'm talking about...(note, some circuits have the fuse on the other end of the on/off switch, but the principle is still the same)

here is a picture that shows the stock setup....lots of amps being pulled a long way and through a ton of contacts and switches
Image may have been reduced in size. Click image to view fullscreen.

now here is a picture showing a relayed circuit. The "switching power is reduced to minimal (can be as low as 4 volts in a lot of cases, putting "zero" load and stress on the VW system. The main power comes directly from the power source through the relay (which is made to handle 30-40 amps, plenty for a VW system)
Image may have been reduced in size. Click image to view fullscreen.
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ENG: 1600cc DP, OE (Mexican) 30mm VW oil pump w/filter running 5w30 full synthetic oil
CARB: 30 PICT-1 (105-1) 52 idle, 122.5 main, & 125z air
IGN: 113905205K w/Pertronix, Bosch 8mm wires, NGK B5HS plugs
EXHST: Stock w/ Peashooters
...And heated seats!
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Joel
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PostPosted: Thu Dec 22, 2011 1:37 pm    Post subject: Reply with quote

I run a relay on mine for the ignition circuit too and it made a huge improvement.

When I had a VW engine still I saw a 2 volt increase at the coil but the biggest improvement was how much faster my wipers operate when they are actually getting 14 volts.

Only comment I will make is if you run any sort of fan in the car on the ignition circuit it can cause feed back which holds the relay coil in.

I was having problems when my A/C was on if I turned the ignition off the car would run for about 1-2secs after till the fan stopped spinning as it was acting a generator and holding the coil in.

Took me a while to twig what it was, I moved the evap fan power to the "X" circuit (74 bug) to get it off the ignition circuit and problem gone.

A diode would also fix the issue.
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badufay
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PostPosted: Thu Dec 22, 2011 3:28 pm    Post subject: Reply with quote

good point, I have no radio noise on mine.... mine also is off the X circuit on the ignition. Another nice thing about the relays is you aren't going to overload that circuit either since its just for switching power. The battery is where the large voltage draws are coming from
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ENG: 1600cc DP, OE (Mexican) 30mm VW oil pump w/filter running 5w30 full synthetic oil
CARB: 30 PICT-1 (105-1) 52 idle, 122.5 main, & 125z air
IGN: 113905205K w/Pertronix, Bosch 8mm wires, NGK B5HS plugs
EXHST: Stock w/ Peashooters
...And heated seats!
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ret1614
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PostPosted: Thu Dec 22, 2011 4:48 pm    Post subject: Reply with quote

Make this a general relay thread?
I'll add a "safe" fuel pump wiring diagram.
Image may have been reduced in size. Click image to view fullscreen.

The ten second prime function can be removed by connecting R2-85 directly to the oil pressure sender.
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badufay
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PostPosted: Thu Dec 22, 2011 6:29 pm    Post subject: Reply with quote

nice! Here is an example of relaying the headlights too... (not mine, but I used this when I did mine, found this from another thread)

Image may have been reduced in size. Click image to view fullscreen.
_________________
ENG: 1600cc DP, OE (Mexican) 30mm VW oil pump w/filter running 5w30 full synthetic oil
CARB: 30 PICT-1 (105-1) 52 idle, 122.5 main, & 125z air
IGN: 113905205K w/Pertronix, Bosch 8mm wires, NGK B5HS plugs
EXHST: Stock w/ Peashooters
...And heated seats!
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ghia4mea
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PostPosted: Thu Dec 22, 2011 7:42 pm    Post subject: Reply with quote

A sad note about relays:
I have purchased several automotive relays at my local parts chain store.
(Advanced Auto Parts)
The relays are marked as 40 amp relays but when I took them apart, inside was soldered a small 5 amp relay.
These relays are of course from china. They look exactly like the regular 40 amp automotive relays that have been available for years at most auto stores.
I mention this just to make everyone aware of this latest rip-off.
Not an issue if your device is low current, but a big issue if you are trying to operate a high current device.
Good Luck all.
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BugMan114
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PostPosted: Thu Dec 22, 2011 7:59 pm    Post subject: Reply with quote

i work at advance auto, and yes, the cheap ones do suck (the ones that are located on the light isle, and in the horn isle). I use the BWD or intermotor ones in the back (the ones that are for fuel pumps, or horns, or whatever). they are much heavier, and last a hell of a lot longer (i have yet to kill one), but i've killed about 3 or 4 cheap relays. the downside, is the nicer ones cost about $20 each.
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Chris Vellat
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PostPosted: Thu Dec 22, 2011 9:10 pm    Post subject: Reply with quote

Relays also don't care about polarity, either 85 or 86 can be wired positive or negative, they just cannot be the same...and on a simple relays with only an 87 that holds true for 30 and 87.

Relays can also supply switched grounds, or be switched by ground, when I wired the relays for the heater booster and rear window defrost in my `69...power is present at 85 and 30 with the key on, and a switch at the dash grounds 86. I used several Autostick insulated lamp holders in the speedometer that also have power with the key, and the switches that supply the relays with grounds also ground the lamps.

I've used 75amp relays to add additional fuse panels to my Bus and my Beetle...and fuse the igntion coil off of that fuse panel.
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ret1614
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PostPosted: Thu Dec 22, 2011 11:10 pm    Post subject: Reply with quote

Be careful about the polarity switchup with 85 and 86. Some relays will burn up if you hook them up backwards... Like the one I use for the 10 second delay. They usually are marked on the diagram on the side positive or negative if it does matter.
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Chris Vellat
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PostPosted: Thu Dec 22, 2011 11:15 pm    Post subject: Reply with quote

ret1614 wrote:
Be careful about the polarity switchup with 85 and 86. Some relays will burn up if you hook them up backwards... Like the one I use for the 10 second delay. They usually are marked on the diagram on the side positive or negative if it does matter.


Oh yes, I meant to say when using simple 'automotive' 12VDC SPST 20/30/40A Bosch/Tyco/Hella style relays.

Quote:
Tyco Electronics has acquired the automotive relay business of Robert Bosch GmbH and is now manufacturing this relay to the original Bosch specifications.


http://ecx.images-amazon.com/images/I/419Oc8wOw3L._SS500_.jpg

http://www.amazon.com/HELLA-003510082-SPST-Relay-B...mp;sr=1-25


Last edited by Chris Vellat on Thu Dec 22, 2011 11:22 pm; edited 1 time in total
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ret1614
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PostPosted: Thu Dec 22, 2011 11:18 pm    Post subject: Reply with quote

Submit requests for relay wiring diagrams? I'll make them, just give me the wiring diagram for the load and the supply.
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Looks like Hell, but she goes the same way.
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dingdow
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PostPosted: Fri Dec 23, 2011 1:11 am    Post subject: relay wiring Reply with quote

I would like to change my headlight, wipers, emergency switches to toggle switches. (I like they way they look and feel). Can you design a wirng diagram to do this for a 68 bug for me?? Thanks - Ding
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MagmaJctAz
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PostPosted: Fri Dec 23, 2011 4:26 am    Post subject: Re: DIY: Here's how to add a Relay to an electrical circuit Reply with quote

badufay wrote:

Adding a relay simply uses the original power wire as a switch to the relay with minimal power required. I'm sure this will offend many because it didn't come stock, so feel free to call me "The P.O."


I'd only complain about you being the "P.O." if you screwed things up. I prefer to keep things stock, don't get me wrong. But a few "enhancements" never hurt. When people start gutting systems because they have no automotive background, and they don't understand, and refuse to learn anything, it upsets me.

This holds true for vehicles other than VWs. I've seen where a vacuum operated vacuum control valve was connected backwards causing a constant vacuum leak. To "correct" that, either the same person, or the next in line disconnected several vacuum lines from the solenoid bank and plugged them with screws. With so many things disabled, no wonder there were problems.

What you are doing is improving an old and worn out system. I've used a relay in my starter circuit for over a decade. Despite popular belief, Ford started solenoids are not needed to bypass the starter circuit in an ACVW. In fact, they pull nearly as much current as the VW starter solenoid. A good automotive relay will work the best because it pulls a small amount of current vs. the Ford option.

I made the change after a trip to emissions here in Arizona. Unfortunately I moved here during the month of July, so my emissions requirement is forever in the summer. I was sitting in line for about an hour. It was so hot I would get out of my Bug and sit under a tree leaving the engine idle. When I pulled in I was instructed to shut the engine off. To my disappointment the "driver" wasn't able to get the engine to start, nothing. They made me leave, and gave me a push. I pop started it as they pushed me out of the bay and drove home.

When I got home I shut `er down and started `er right back up. I was pissed. I went to Radio Shack and bought an automotive relay and installed it under the back seat. I've never had a failed start for that problem since. (I have had rabbits eat my starter wire however!)
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PostPosted: Fri Dec 23, 2011 5:46 am    Post subject: Reply with quote

Chris Vellat wrote:
Quote:
Tyco Electronics has acquired the automotive relay business of Robert Bosch GmbH and is now manufacturing this relay to the original Bosch specifications.


http://ecx.images-amazon.com/images/I/419Oc8wOw3L._SS500_.jpg

http://www.amazon.com/HELLA-003510082-SPST-Relay-B...mp;sr=1-25

I'd buy the SPDT version of the relays. They have the same terminals numbers plus an additional 87a terminal which is normally closed with 30 when the relay is NOT energized. They are more common and therefore less expensive... even for real Tycho (previously Bosch) brand:
http://www.amazon.com/Install-Tyco-Relay-Volt-Each/dp/B000P61E36/

PartsExpress carries a variety of relays and harnesses:
http://www.parts-express.com/wizards/searchResults.cfm?srchExt=CAT&srchCat=746
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PostPosted: Fri Dec 23, 2011 6:42 am    Post subject: Reply with quote

Could someone tell me how to wire these relays?

Fused Relay from a 79 rabbit fuel pump #896321, it has 30,87,15,31,31b
Relay from Gm cars #14100455, it has 30,85,86,87,87a

Also how can I tell the Amps on a relay?

A relay would help out power windows right (on another car)?
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mondshine
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PostPosted: Fri Dec 23, 2011 8:57 am    Post subject: Reply with quote

The "Rabbit" fuel pump relays are the best way to go for wiring an electric fuel pump.

30 is connected to Battery+ (fused!)
15 is connected to Ignition (+12V with ignition switched on)
31 is connected to chassis ground
31b (sometimes labeled 1) is connected to terminal 1 of the ignition coil; where the green wire from the condenser is connected.
87 is the supply current to the pump; it will show +12V with the ignition switched on and the engine turning.

Good luck, Mondshine
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PostPosted: Fri Dec 23, 2011 9:03 am    Post subject: Reply with quote

banditwolf wrote:
Could someone tell me how to wire these relays?

Fused Relay from a 79 rabbit fuel pump #896321, it has 30,87,15,31,31b
Relay from Gm cars #14100455, it has 30,85,86,87,87a

Also how can I tell the Amps on a relay?

A relay would help out power windows right (on another car)?



http://www.truckerac.com/blower-relay-chevroletgmc-oem-22552019814100455.html
The GM relay looks like a regular SPDT relay...there's usually an indication of the amperage limit on the housing...according to this website it may be 30/40A.

The Rabbit fuel pump relay is easy, the German wiring system went unchanged. We know 30 is used as fused power, 87 will feed the device, 15 is ignition coil power, 31 is ground, and 31B is intermittent ground - which in this case comes from the negative side of the ignition coil (same as the tachometer and condensor)
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PostPosted: Fri Dec 23, 2011 9:50 am    Post subject: Reply with quote

Relays allow low amperage control switches function high amperage tasks,they are used in modern cars to reduce cost of components and wiring.

Use in Volkswagen applications,from starter relays to headlight relays is generally to mask a failing switch,harness or component.Much easier and less complicated to repair the bad Vw component than to wire in a relay.
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PostPosted: Fri Dec 23, 2011 10:13 am    Post subject: Re: relay wiring Reply with quote

dingdow wrote:
I would like to change my headlight, wipers, emergency switches to toggle switches. (I like they way they look and feel). Can you design a wirng diagram to do this for a 68 bug for me?? Thanks - Ding


Sell the '68 and buy a 1303. You will get what you want except the wipers.
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badufay
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PostPosted: Fri Dec 23, 2011 10:16 am    Post subject: Reply with quote

Gotta hard time believing that you're not showing a 3% voltage drop on your coil even with good wiring....
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ENG: 1600cc DP, OE (Mexican) 30mm VW oil pump w/filter running 5w30 full synthetic oil
CARB: 30 PICT-1 (105-1) 52 idle, 122.5 main, & 125z air
IGN: 113905205K w/Pertronix, Bosch 8mm wires, NGK B5HS plugs
EXHST: Stock w/ Peashooters
...And heated seats!
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