Hard Start Relay Fuse Keeps Popping

[OLDveedubs]

Here is a little background info.

About a year or so ago I installed a 6 volt hard start relay from Wolfsberg West. Works great, car starts most of the time except after a long drive (starter gets pretty toasty). I end up having to take a drink break, walk around a bi,t and it usually cranks over.

Now after two long tripsI have had the following problem. I will get to my destination after about 2 hours of driving. The engine is a 1600sp w/ PICT 30/31 carb, SVDA dizzy, running oil temps below gene berg light indication, rpm is about 3200 most of the time.

When I get to my parking spot I shut the car down. Then I go and try to start it up again just to see...nothing happens. The dummy lights dim a little but the starter doesn't even remotely turn over. I've narrowed it down to the 15 amp fuse on the hard start relay. The question is...why does it keep blowing? All the connections are good and tight. The ground wire is attached to a screw on the inspection plate.

Weird thing is the last time I put a fuse in the next morning...started up fine when it was cold. Worked for about a week then I went on another trip...blew again. Any ideas? I'd hate to have to push start everywhere!
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-Ryan
Restoration Updates
www.my59bug.com
"Perfection through inspection."

[glutamodo]

The fuses that come with the hard start relays are too small. Even the 12V kits come with a 15 amp fuse. If you ever read the specs on the starter solenoid pull-in current, you'll see this:

The pull in current is momentary, but can be enough to pop a fuse - just look at the rating for the 6V - 89 amps on the Bosch starter. Which I think HAS to be a misprint, I think 39 amps is more likely. Still, that's a lot. Momentary loads won't necessarily pop the fuse, but the steady "holding current" of 18-23 amps will. You can see that's not matched for a 15 amp fuse.

Even on the 12V the 30-35 pull in amps can be enough to pop that 15 amp fuse, even if the holding current is only 11 or 12 amps. When we would install the 12V kits into customers cars we'd always put 25 or 30 amp fuses into them.

andy

[OLDveedubs]

thanks for the tip. i had a couple extra fuses that i tried earlier today (bought some after the first problem, 15a) and they did the same thing. so i will look for a 30 amp fuse tommorow. thanks again!

if there are any other comments let me know!
_________________
-Ryan
Restoration Updates
www.my59bug.com
"Perfection through inspection."

[Pfc J]

I had the same problem with the 15A.

The 20A I have in there now has never given me a problem, even in the winter.

[codubdude]

Glutamodo is correct. When he worked with me 6-8 years ago he was the shops' electrical tech. We did opt for the 30 amp maybe more for washboard roads but I believe a previous responder went for the 20 amp. Either way, the 15 amp was incorrect from the get go for most of us. Brian

[KTPhil]

Interesting fact is that the original starter circuit did not have fuse protection. You have added one to the relay tripping circuit, and that's what's blowing?

[DaBraink]

How old is the starter? Is the bushing possibly worn? If the armature is riding close to the stator, heat may aggravate the problem by allowing it to drag.

I had a Chevy starter that was too close to the headers and had to wrap the header and starter to insulate them. After that I never had a problem with high current draw. It was so high the fusible link would burn.
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If it ain't broke.................find something else to fix.

There's never enough time to do things right, but always enough time to do them over.

[FL-Frank]

[KTPhil]

None of them.

Your hard start relay circuit should add its own fuse on its line from the main power/battery to the starter.

[glutamodo]

Yep, if the car is still wired as per the factory, the current goes straight from the voltage regulator to the headlight switch, then from there via a junction at the fusebox to the ignition switch and out from there to the starter without a single fuse in between.

Now, Low Voltage Relay kits usually add an inline fuse, but not always, as I have seen them before where it was just a relay socket with wires coming out and no inline fuse holder.



Blast from the past, this thread is. I see a dead image link above from me, that was because I had a very small amount of images on a different FTP server that got taken down. Although the image isn't essential, as I discuss the pertinent specifications in text, I do have that image available elsewhere:

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Andy T.


IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox.

[FL-Frank]

Thanks Andy.

Yes, the car ('64 Ghia) is wired as it came from the factory. The relay I got from WW has no provision for an inline fuse.
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“Tinker Toy” 1967 Savannah Beige Beetle Sedan...........Mostly Original Survivor
“Fritz” 1964 Gulf Blue Karmann Ghia Coupe...Complete Pan-Off Restoration SOLD

[glutamodo]

Okay, so it's WW, I looked it up and that's the kind of kit that I've seen before that was not assembled with an inline fuseholder. The Bosch WR1 (12V) kit was the one where it had a harness with a fuseholder and the too-wimpy 15A fuse.

It's up to you if you want to get an inline fuseholder and splice it in there.

_________________
Andy T.


IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox.

[bluebus86]

[glutamodo]

Pull-in current is momentary, so not nearly as big of a deal as the holding current, which is constant while the starter is in operation.

Although, if you're around parts cars, the "horn relay" that VW used for many years as a power supply relay, those are commonly rated at 40A. In the watercooled era they even grew ginormous power in/out terminals.

_________________
Andy T.


IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox.

[herbie1200]

Current Values posted by glutamodo I think shall be divided by ~2 in normal cars.

They are measured with 135A/h batteries; with a normal 55Ah or 66Ah battery voltage drop should cause a proportional current drop.

[glutamodo]

Just because you have that kind of available electrical potential doesn't mean that the device in question will actually USE it. Also, the type 2 6V testing procedure mentions nothing about that kind of power source.
_________________
Andy T.


IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox.

[herbie1200]

The matter is that under load a normal battery drops a lot of voltage, so the calcuation should take into account (Ohm's relation) the actual voltage to which current flow is directly proportional.

Measuring with 2 or 3 battery in parallel is not for their capacity (measured in Amperes per hour) but for the parallelizing of their internal equivalent resistance.