Need help with 6v hard start relay

bluebug66 · Post by **bluebug66** » Sun Apr 01, 2007 10:47 am

I installed a hard start relay kit on my 66. It is from Wolfsburg West. It came with an inline 15 amp fuse and I have been having a problem with the fuse blowing during starter operation. Is 15 amp the correct size for the 6 volt system? Is the fuse seeing the solenoid amp draw or just the relay coil amps? Thanks.

Speedy Jim · Post by **Speedy Jim** » Sun Apr 01, 2007 1:35 pm

If the fuse connects to Term #30 on the relay, it sees all the solenoid
current draw.

The 6V solenoid can draw between 35 to 40 Amps (!) when it first pulls in.
(There are 2 windings and the hold-in current is less.)

Substitute a 30 Amp Slo-Blo (or whatever automotive fuse you can find)
and see if that cures it. Even better would be a 30 Amp automotive
circuit breaker.

MNAirHead · Post by **MNAirHead** » Mon Apr 02, 2007 8:46 am

Speedy (or whoever)

Is there a rule of knowing when we can convert to a slow blow fuse?

Speedy Jim · Post by **Speedy Jim** » Mon Apr 02, 2007 9:21 am

In general, when the load has a high peak "inrush" current
which later drops off, a Slo-Blo fuse is good. Circuit Breakers (most) have
an inherent slow-to-trip feature.

Motors are a good example of loads which draw a lot of current
on initial start-up (wiper motor). The solenoid on the starter motor is a very
special case, but it does draw a huge current to initially pull-in.

MNAirHead · Post by **MNAirHead** » Mon Apr 02, 2007 9:26 am

So the time frame being like a second or so?

Speedy Jim · Post by **Speedy Jim** » Mon Apr 02, 2007 1:20 pm

Yeah, 1 second is probably good. Fuse mfr publish complicated
curves covering every contingency <g>.

Post by **2088 bob** » Mon Apr 02, 2007 1:59 pm

This inrush current that speedy jim speaks only lasts for micro seconds here is an example of inrush current

my wife's filter queen vacuum draws 7 amps running but on start up i have seen it pin 80 amps on my meter but this is just for a micro second so some fuses are designed to get around this and as speedy jim said breakers react even slower

bluebug66 · Post by **bluebug66** » Fri Apr 06, 2007 6:20 am

Update. I put a 30 amp ATC fuse in it and have not had any more problems. I also found that I had a problem with the starter bushing and replaced it, so it may have been a combination of these two things causing it. Thanks for the advice.