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Tue Jun 29, 2010 4:42 pm

I need a little help with the hard start on my 74 Super. We were making a 150 mile drive in the car this past weekend and about the halfway point, I pulled over just to spot check the car and take a quick break.

When I was ready to go, I turned the key and nothing. I had lights and everything, but the motor just would not turn. I do know that I have a hard start relay underneath the back seat and I was just going through the wiring diagrams that I got from this site. I am a bit confused from what I am reading here and what I am seeing in my car. This certainly appears to be factory installed (I am guessing) and looks to be the J9 area from the schematic http://www.thesamba.com/vw/archives/info/wiring/74-up113wiring.jpg

However it is wired a bit different.

From the Bosch Relay;
30 - Positive Battery
85 - Ground
86 - Small Black wire that goes to the wiring harness to the front. According to the schematic, this goes to the rear window defroster switch
87 - Start Solenoid Terminal
87 - Diagnostic Port Blue/White wire (yes, there are 2 87's)

The Big Red/Black wire that appears to go to the Ignition Switch does not attach here at all. So, did someone do a half-way job on this bypass switch at some time in it's past? Should all I need to do is disconnect #86 and install the Red/Black wire? The Red/Black wire does have a lug here so, it is a very simple job to do. Would I need to do anything to the loose end of this wire? Finally, is there a way to test this relay to make sure it still works?

Thanks for the help!!

Tue Jun 29, 2010 5:33 pm

It looks like someone re-purposed the rear window defroster relay.
If you turn on the defroster switch near the fuse box does the starter turn the motor over?

The pin out on the relay sounds similar to the common Bosch SPDT relay. Pins 85 & 86 are the +/- to energize the relay.
30 is the input which is connected to 87 once the relay is energized.
There's nothing wrong with using this relay for your hard start circuit. And yes, if you use the red/black wire from the ignition switch instead of the black wire from the defrost switch, it should do what you want.

Tue Jun 29, 2010 5:35 pm

http://www.glenn-ring.com/tech/relay_starter.htm

Tue Jun 29, 2010 6:19 pm

Maybe this view of the area under the rear seat bench will help you.

In the top photo, aside from some extra items, is the connector for terminal 50 of the starter. The heavy red wire originates at terminal 50 of the ignition switch, and runs through the gray jacket and the grommet to the starter.

In the bottom photo, the hard start relay is "arted in".
When the key is in the "start" position, the relay is energized, and connects terminal 50 of the starter to battery +.
A fuse in that line (or any wire connected directly to battery +) is a good idea.
Terminal 86 of the relay is connected to ground.

It's best to have this relay "inside the car" where it is out of the elements, clean and dry.

:!: Before you do any of this, make absolutely sure that the connection at the starter terminal 50 is clean and tight. This type of connection can easily weaken from fatigue. You might just solve the problem by fixing that connection at the starter.
Good luck, Mondshine

Tue Jun 29, 2010 7:50 pm

Thanks all for the help.

Turns out I mis-followed the starter terminal connector back. This was completely stock and the relay was in fact hook to the rear window defroster circuit as it was when it was made in '74. There was no hard start involved here at all.

So, I did clean the terminal on the solenoid, tightened the lug up a bit with a pair of pliers. I also wired up the hard start relay and it clicks when I turn the ignition.

Good to go!

Wed Jun 30, 2010 6:25 am

Glenn wrote: http://www.glenn-ring.com/tech/relay_starter.htm

Glenn, about this relay here...Seems the wires for power and to the solenoid are too small. Even the Germans used larger gauge wire. Why the fuse? Fuse size is based on wire size. When it comes to wire larger is better.

Wed Jun 30, 2010 6:30 am

runamoc wrote: Glenn, about this relay here...Seems the wires for power and to the solenoid are too small. Even the Germans used larger gauge wire. Why the fuse? Fuse size is based on wire size. When it comes to wire larger is better.
My relay uses the same size wire and had not had a problem in the 15 years it's been in use.

Larger can't hurt but this works for me.

Wed Jun 30, 2010 6:37 am

Folks, don't take this the wrong way as I am guilty as well:

what is kind of funny about this whole 'hard start relay' issue is that if you look at how the VW starter is wired, it has a relay built into it. However, the relay seems to require a large amount of power to activate it.

I am now building up a rail buggy and it too will have a 'hard start relay' wired in. Call me crazy but I am not a big fan of large amounts of electrical power cruising through the wiring harness if it is not necessary....

Sun Apr 17, 2011 3:02 pm

mondshine wrote: Maybe this view of the area under the rear seat bench will help you.

In the top photo, aside from some extra items, is the connector for terminal 50 of the starter. The heavy red wire originates at terminal 50 of the ignition switch, and runs through the gray jacket and the grommet to the starter.

In the bottom photo, the hard start relay is "arted in".
When the key is in the "start" position, the relay is energized, and connects terminal 50 of the starter to battery +.
A fuse in that line (or any wire connected directly to battery +) is a good idea.
Terminal 86 of the relay is connected to ground.

It's best to have this relay "inside the car" where it is out of the elements, clean and dry.

:!: Before you do any of this, make absolutely sure that the connection at the starter terminal 50 is clean and tight. This type of connection can easily weaken from fatigue. You might just solve the problem by fixing that connection at the starter.
Good luck, Mondshine ok so if i fallow the second pic with a 25amp fuse from betw the battery wire and the #30 i should be ok then right?? #87 and #85is the same wire just spliced into the relay.....87a not used...#86 just to a good ground ....it looks simple enough , but i just like to double triple check ....

Sun Apr 17, 2011 11:39 pm

These two images may help with understanding how the "Bosch-style" relay functions.

This is the connection between #30 and #87a when the relay is NOT powered/energized:

This is the connection made between #30 and #87 when current flows through the #85+#86 terminals (in either direction); the relay is powered ON:

So in the images above, when terminal #85 receives 12v+ from the ignition switch it energizes the coil inside the relay (grounded via #86 terminal connection). This forces a connection (aka a short) between #30 and #87 terminals. This allows 12v+ from the battery to flow directly to the starter solenoid.

Mon Apr 18, 2011 3:55 am

runamoc wrote: Glenn wrote: [/img]

:shock: WTF is that???

Mon Apr 18, 2011 4:07 am

I may be wrong but I believe it's called a.......Battery :lol:

Mark33563 wrote:
what is kind of funny about this whole 'hard start relay' issue is that if you look at how the VW starter is wired, it has a relay built into it. However, the relay seems to require a large amount of power to activate it.

Can you expand on that alittle further?

Cos it's a lack of a relay that causes the problem.

You have the power going all the way to the front from battery, then through the tiny little contacts in the ignition switch then all the way to the back and having to pull in a big starter solenoid.
No relay involved.

Adding the relay takes all that out of it, just a nice short run straight from the battery to the solenoid.

Relay coils don't take a huge lot of power to pull in, but once pulled in only need about 5 volts to stay that way.

Mon Apr 18, 2011 4:22 am

Joel wrote: I may be wrong but I believe it's called a.......Battery :lol:

. I was referring to the cluster of wires :lol:

Mon Apr 18, 2011 4:26 am

I know, I just couldn't resist. :wink:

You want WTF? you should see what lurks beneath my backseat :shock:

Mon Apr 18, 2011 7:43 am

vw_hank wrote: runamoc wrote: Glenn wrote: [/img]

:shock: WTF is that???

What the Germans would have done if they didn't care how much it cost in extra wire. :lol:

Mon Apr 18, 2011 7:56 am

Joel wrote: Mark33563 wrote:
what is kind of funny about this whole 'hard start relay' issue is that if you look at how the VW starter is wired, it has a relay built into it. However, the relay seems to require a large amount of power to activate it.

Can you expand on that alittle further?

Cos it's a lack of a relay that causes the problem.
I understand what Mark33563 is talking about. The starter solenoid is itself a large relay. When you energize the #50 terminal it energizes a coil that pulls on an actuator. That actuator does two things...
1) Pulls on the pivot arm that will extend the drive gear to engage the flywheel teeth

2) Connects (shorts) the two large terminals on the solenoid. This transfers power from the battery cable to the starter motor and gets it turning (cranking).

So just like the small Bosch-style relays, the starter solenoid uses a small current (<20A) from the ignition switch to allow a large current (~150A) to flow from the battery to the starter motor.... ala Relay.

Mon Apr 18, 2011 5:00 pm

Thanks Ashman, you beat me to it.

Essentially what the 'hard start' relay setup does is that it takes even less power to activate the relay/solenoid in the starter.

It diverts the needed power from running from the battery, through the ignition switch, and back to the starter solenoid directly from the battery to the starter solenoid.

If it is of any consequence, I run/have run a 'hard start' relay on all my VW's ever since my first VW.

Mon Apr 18, 2011 6:56 pm

What some may not understand is in a 12 volt system and worse in a 6 volt system, there is what is called voltage drop. the longer the wire the more resistance, therefore the more voltage drop you have. So when you have a voltage drop concern, you can address it by using larger wire or get rid of some wire by using a relay. The relay short cuts the factory wire, thus reducing voltage drop so you get more power to your starter solenoid and the starter solenoid will draw less amps and last longer 8)

Mon Apr 18, 2011 8:14 pm

Just one more thing concerning voltage drops...the ground side of the start ciruit depends on that flex strap that connects the trans/engine to the frame electrically. If the strap is missing, or if it has poor contacts to either the frame or tansmission, you will have start circuit problems.

In the picture with the multiple positive leads, one might suggest a ground side jumper to the gen or alt case , as well as a ground wire run directly to the dash area. No longer depend on grounding your electrical circuits through aging frame contacts. Use 8 gauge wire.

I have also experienced problems with starters that had soldered connections, especially poorly rebuilt starters. A condition can exist wherein solder joints that are cold, contract and make connection. As the engine compartment heat warms the starter and its connections, the expansion no longer allows electrical contact. You then have a starter that fails when warm and starts when cold.

Mon Apr 18, 2011 8:57 pm

Quote: In the picture with the multiple positive leads, one might suggest a ground side jumper to the gen or alt case , as well as a ground wire run directly to the dash area. No longer depend on grounding your electrical circuits through aging frame contacts.

I went over those too.