Double Relay Diagram +/-

Post by **Amskeptic** » Sat Dec 20, 2008 4:42 pm

I will be doing a write-up in . . . gee, which forum?
Fuel System? Electrical? Engine?

By the way, for you sharp eyes out there, there is a whopper of a lie that I have not explained in this diagram. What is it?
Colin

vwlover77 · Post by **vwlover77** » Sat Dec 20, 2008 4:46 pm

Hmmmm... I wouldn't call it a whopper, but the "Cold Start Valve" should really be labeled "Thermo Time Switch" with the cold start valve downstream from it.

Or did I miss something else more obvious?

Post by **Amskeptic** » Sat Dec 20, 2008 4:50 pm

vwlover77 wrote:Hmmmm... I wouldn't call it a whopper, but the "Cold Start Valve" should really be labeled "Thermo Time Switch" with the cold start valve downstream from it.

Or did I miss something else more obvious?

Ha HAHA! No, no. The cold start valve is in fact powered directly from the double relay. Then the ground path for the cold start valve is grounded at the thermotime switch. Thanks for playing, no big stuffed Dick Cheney Bear for you!
Colin

vwlover77 · Post by **vwlover77** » Sat Dec 20, 2008 5:00 pm

Dang it! That's right. How about a consolation prize for pointing out that the wire from the coil does not go directly to the double relay, but to the ECU first?

dtrumbo · Post by **dtrumbo** » Sat Dec 20, 2008 5:48 pm

The AFM isn't connected to the fuel pump.

Again, beautiful artwork. I can't wait to purchase the book/calendar/tattoo/whatever that compiles all of these.

Post by **Amskeptic** » Sat Dec 20, 2008 8:51 pm

vwlover77 wrote:Dang it! That's right. How about a consolation prize for pointing out that the wire from the coil does not go directly to the double relay, but to the ECU first?

BZZZZZZZZZZZZZ. You'd be wrong again! Now we have to take back the stuffed bunny from your little daughter.

The #15 terminal on the coil is where the double relay gets its 12 volts to supply fuel pump and ECU and injectors. It is a black wire that runs along with the reverse light wire.

The #1 terminal on the coil happens to inform the ECU of the rpm signal, yes, but. . . we're not there yet!
Colin IAC Midway Step Right Up

Post by **Amskeptic** » Sat Dec 20, 2008 8:53 pm

dtrumbo wrote:The AFM isn't connected to the fuel pump.

Again, beautiful artwork. I can't wait to purchase the book/calendar/tattoo/whatever that compiles all of these.

We have a WINNER! You are correct.
Here's your plastic-red-faced Cheney Stuffed Shirt Doll, pull his little voice activating cord and hear him tell congressmen to "f*** off."
. . . so. . . how 'zactly does the AFM turn on the fool pump anyhoo? Bonus points.

zblair · Post by **zblair** » Sat Dec 20, 2008 8:54 pm

Okay, this isn't the poll thread but I have to admit here that the reverse drawings are growing on me. I think in this case it is easier for my damn tired eyes to see what is pictured

zblair · Post by **zblair** » Sat Dec 20, 2008 8:55 pm

Amskeptic wrote: . . . so. . . how 'zactly does the AFM turn on the fool pump anyhoo? Bonus points.

okay, I know nothing about this, but through air pressure since it is an air flow meter???

Post by **Amskeptic** » Sat Dec 20, 2008 9:32 pm

zblair wrote:
Amskeptic wrote: . . . so. . . how 'zactly does the AFM turn on the fool pump anyhoo? Bonus points.
okay, I know nothing about this, but through air pressure since it is an air flow meter???

You are correct! You know nothing about this!

But, as a consolation prize, I will offer the following hint:

Airflow meter does close the contacts that allows 12 volts to flow from a power relay output (destination) terminal (88a) to where? What does it actually do when it gets there?
Colin

chitwnvw · Post by **chitwnvw** » Sat Dec 20, 2008 9:50 pm

Dumb as a post I am. What with livin' in the heartland, I am. Still I'd buy me one of your books...if you ever publish it.

Post by **Amskeptic** » Sat Dec 20, 2008 10:08 pm

chitwnvw wrote:Dumb as a post I am. What with livin' in the heartland, I am. Still I'd buy me one of your books...if you ever publish it.

Wish me a little luck. I am 49 and suffering a little ADHD in the midst of the daunting task.

Anyways, the diagram above is made simple to get you warmed up to the simple fact that the double relay is a simply a start-induced voltage supply that switches over to a run-induced voltage supply. The tricky thing is that the AFM can't run the fuel pump as illustrated. It would melt those delicate contacts in the AFM. It actually fires up the "pink" relay to keep the fuel pump going. There are two critical diodes (one way valves) in the double relay to prevent "backflow" that I will explain in the Big Cajunga Diagram coming up. . . with explanations for all diagrams when I park it in the fuel? engine? electrical? forum.
Colin

dtrumbo · Post by **dtrumbo** » Sun Dec 21, 2008 6:23 am

Amskeptic wrote:Here's your plastic-red-faced Cheney Stuffed Shirt Doll, pull his little voice activating cord and hear him tell congressmen to "f*** off."

Woo hoo! I'll sell it on eBarf to someone (like my in-laws) still crying (or is that peeing?) in their cornflakes about how we're DEFINITELY going to suffer a terrorist attack now that Obama's in office (which he isn't yet, but these types don't stand on fact-based discussion). Perhaps I'll soak 'em for enough $$$ to pay for my IAC visit next summer!

Amskeptic wrote:. . . so. . . how 'zactly does the AFM turn on the fool pump anyhoo? Bonus points.

You beat me to it, but that's the whole point of the right side of the double relay. It is so simple yet works so well and provides such a huge safety function. I'm still giggling over the comment made in another thread to the effect of how the Germans weren't known for their electrical engineering skills.

VWBusrepairman · Post by **VWBusrepairman** » Sun Dec 21, 2008 7:36 am

Amskeptic wrote: The #15 terminal on the coil is where the double relay gets its 12 volts to supply fuel pump and ECU and injectors. It is a black wire that runs along with the reverse light wire.

Whenever the starter is engaged, the relay activates the fuel pump and supplies current to the cold start system (thermo-time switch, cold start valve).

It's important to note that once the electricity reaches those injectors, they work best with about 3-5 volts. The resistor pack reduces the 12 volts available from the power relay whenever the ignition is on.

Good write up, for a 49 yr. old.

Put me a copy of the manual on reserve.

turk · Post by **turk** » Sun Dec 21, 2008 7:41 am

VWBusrepairman wrote: Put me a copy of the manual on reserve.

Me too.

Itinerant Air-Cooled

Itinerant Air-Cooled

Double Relay Diagram +/-

Double Relay Diagram +/-