TheSamba.com :: View topic

Fri Feb 24, 2023 6:47 pm

After a long hiatus, I have returned my attention to my 74 Super Beetle.

I ordered a hard start relay from Wolfsburg West. The one they sell doesn't
have an inline fuse from the relay to the battery. Can I get away with not using the fuse?
https://www.wolfsburgwest.com/cart/DetailsList.cfm?ID=111998611A

If I have to splice one will this one that I can get from
AutoZone work? and would a 15 or 20 amp fuse be good enough?
https://www.autozone.com/starting-charging-and-mis.../32415_0_0

Thanks.

Fri Feb 24, 2023 7:26 pm

https://www.thesamba.com/vw/forum/viewtopic.php?t=777033

Good tidbits in there ^ ^ ^ I remember following that thread recently and it came to mind when I saw your thread. Glutamodo and Ashman always have solid input, and there are a ton of good threads on this subject.

Fri Feb 24, 2023 7:38 pm

kirk1015 wrote: After a long hiatus, I have returned my attention to my 74 Super Beetle.

I ordered a hard start relay from Wolfsburg West. The one they sell doesn't
have an inline fuse from the relay to the battery. Can I get away with not using the fuse?
https://www.wolfsburgwest.com/cart/DetailsList.cfm?ID=111998611A

If I have to splice one will this one that I can get from
AutoZone work? and would a 15 or 20 amp fuse be good enough?
https://www.autozone.com/starting-charging-and-mis.../32415_0_0

Thanks.

The starter circuit pulls way more amps than 15 or 20 amps. I wouldn't try to use a fuse there. The decreased amperage is through the electrical part of the ignition switch when one uses a hard start relay.

For example: my 1988 Mazda truck has an 80-amp big fuse in the engine compartment for stuff BUT NO FUSE OR FUSIBLE LINK directly to the starter.

Sat Feb 25, 2023 4:03 pm

Your starter doesn't have a fuse between the battery to starter so why would a hot start relay need one? just use gromets for any through body panel wiring.

Sat Feb 25, 2023 4:11 pm

I fused mine.

Blue fuse is 15 amps.

Sun Feb 26, 2023 7:30 am

The starter motor draws 100A+ so placing a fuse in the battery cable between the positive post and the stud on the starter solenoid isn't practical.

The ignition switch and hard start relay (HSR) are there to power just the starter solenoid (mounted to the starter motor) which in turn closes the contacts which power the starter motor. The solenoid draws only around 15-25A. So if you add a fuse to the wire between the battery post and the #30 terminal of the relay, a 20A or 25A fuse should be fine.

Did VW fuse this solenoid circuit? No.
Should you, as you install the HSR? Probably.
It is a very short circuit from the battery to the relay to the solenoid. Maybe slightly longer than a meter. Much shorter than the 7m circuit running thru the ignition switch. But since you are building this circuit as part of installing the HSR, go ahead and add a fuse between the battery and the relay.

Sun Feb 26, 2023 8:26 pm

ashman40 wrote: The starter motor draws 100A+ so placing a fuse in the battery cable between the positive post and the stud on the starter solenoid isn't practical.

The ignition switch and hard start relay (HSR) are there to power just the starter solenoid (mounted to the starter motor) which in turn closes the contacts which power the starter motor. The solenoid draws only around 15-25A. So if you add a fuse to the wire between the battery post and the #30 terminal of the relay, a 20A or 25A fuse should be fine.

Did VW fuse this solenoid circuit? No.
Should you, as you install the HSR? Probably.
It is a very short circuit from the battery to the relay to the solenoid. Maybe slightly longer than a meter. Much shorter than the 7m circuit running thru the ignition switch. But since you are building this circuit as part of installing the HSR, go ahead and add a fuse between the battery and the relay.

Thank You Ashman.
I was hoping you would see this.
Why didn't VW do the HSR from the Factory? Weren't most cars by the time of my 74 Super using these relays?

Mon Feb 27, 2023 4:50 am

If you use a fuse, put it close to the battery on the battery+ to relay 30 wire.

It might not be necessary, but I would use a >50A relay, not that the higher rating is needed, but it don't hurt. They usually also have a resistor over the relay coil, again maybe not necessary but will add to the protection (less voltage spike and arking). But the main reason I would use them is they usually comes with wider spade connectors for relay 30 and 87 connections (6.3mm vs 4,8mm) and its not a bad idea to have a larger connection and possible using larger wires battery -> 30 -> 87 -> solenoid. I mean they cost just slightly more and the work installing it is the same.

Mon Feb 27, 2023 9:54 am

kirk1015 wrote: Why didn't VW do the HSR from the Factory? Weren't most cars by the time of my 74 Super using these relays?
Let me put it this way.... my old '75 Beetle (which I no longer have :( ) came to me with an OE VW ignition switch. It worked fine for a few years before I replaced it because the internal contact were burnt. I confirmed this by taking it apart and cleaning the contacts and reinstalling the switch while I waited for my aftermarket switch to arrive. That OE switch was nearly 40yrs old when it failed! So clearly, the starter solenoid circuit (#50), as designed by VW, did not require a HSR... it lasted nearly 30yrs+ before it finally failed. Even if it had lasted only 20yrs, it well exceeded the lifespan expected of a economy car.
This is one of the problems with maintaining 40yr+ old cars... if an OE part that is 20yrs+ old fails you can't really fault the part. At 20yrs+ it well exceeded what could be described as a typical factory part lifespan.
If the aftermarket replacement part doesn't last as long, it is not necessarily a design flaw from VW. For example, if your harness wires are over 20yrs old (as many of our cars are) you cannot expect the same performance as the car had on day1 from the factory. The wires will have higher resistance and less current makes it to the end of the circuit. This is not a "VW design problem", this is a "your car is old" problem. :o

My '75 Beetle's replacement aftermarket ignition switch died after less than 2yrs. I opened it up and found the contact surface for the different circuits were MUCH smaller than the OE switch (which I had already thrown away). See this pic of the contacts from that failed switch:

Note the black/burnt spot along the outer edge around 1-o'clock in the pic. The #50 terminal brass is rather long, but the contact area is just the upper end which is blackended from the relatively high current flow each time the key is turned to START. I don't have a pic of the OE VW switch and its contact area but I can assure you it was closer in size to the center contact point for #30. This larger contact area allows the switch to last longer passing higher current loads.
If you are installing one of these aftermarket ignition switches, you really NEED to install a HSR to offload the solenoid current from the ignition switch contacts. The same applies to the #15 and possibly the #X circuits as you can see they too have small raised contact areas that could get easily burn over time.

Even if you still have an OE VW ignition switch still in the car... adding a HSR will reduce the current flow thru the semi-burnt contacts and extend the life of that switch before it finally fails. Maybe you get another 5-10yrs from the switch?!

Mon Feb 27, 2023 10:14 am

20 years and counting for my switch after installing the relay (and 20 years for the relay too ;-).

Mon Feb 27, 2023 1:48 pm

I had the WW hard start relay in my 1974 Sun Bug. I used a 20 amp fuse where Glenn's is. Never a problem starting in 10 years.