• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Overdrive fusing question on BN6

Share this page

bighealeysource

bighealeysource

Luke Skywalker
Country flag
Offline
Hey y'all,
I have an inline fuse for my O/D between the solenoid and overdrive relay as extra protection. Use a 25 amp fuse and thinking maybe that is not high enough amps as it has blown twice now while everything was working perfect, engaging in and out, and even have a new solenoid. Should I be running a 35 amp or even higher as know it pulls a lot of amperage when actually engaging the solenoid ?
Thanks,
Mike
 
Norman Nock advises 50 A in his "Tech Talk" page 16

Edit; might be a typo error, see later posts

Hans
 
Should I be running a 35 amp or even higher as know it pulls a lot of amperage when actually engaging the solenoid


:nonono:

N O!! there is a big misinterpretation here.

That is an inductive transient of a very short duration and consequently should not be treated as a steady state current.

Use as a maximum a 10 Ampere slow blow fuse

.There are no conventional watts drawn here just a small amount of energy calculated in Jules.--Fwiw--Keoke
 
Hey all
Hoped someone would weigh in ! The in line fuse holder - old type with glass fuse- had just barely melted at one end which pulled the contact away from the glass fuse, my concern now would be what caused that ! I have all new electrics
being overdrive relay, solenoid and throttle switch so cannot imagine what would be causing that. But, it could have been going bad over the past couple of years and did not notice. I'll put in a 10 amp and see how it does.
Thanks,
Mike
 
Mike , make sure that your mechanism in the of is adjusted properly so that when the solenoid engages is engages fully. If you try to lift the ball up too high your solenoid will only partially engage and you will overamp it burning any fuse. Check the amp draw on the solenoid on the bench to see what it draws. I burned my solenoid down and the wiring harness going to it that way. Readjusted the lift on the ball , now all has been fine for 5 yrs.
 
Hi All,

Finally got power back after Irene this afternoon (Saturday) and this is my first response.

First, I have installed an in-line fuse and recommend you exchange your glass fuse holder for an in-line blade or mini-blade fuse holder from RadioShack (about $1.98). Although I have no problem with glass fuses, the blade type are more easily accessible and your glass fuse or holder could be corroding internally.

Second, the solenoid draws under 10 amps if working correctly and, since you are trying to protect the solenoid and WIRING, I have had no difficulty using a 10 amp fuse. I suggest you try a 10 amp fuse and, if it blows, you go higher. However, I recommend you use a maximum of 15 amps as you harness or components may be masking a corrosion problem.

I am a little surprised that Norman Nock would have ever recommended a 50 amp fuse of any type (including UK which is about 30-35 amp US). These are welding amperages and would tolerate the burning of your harness.

Good luck,
Ray (64BJ8P1)
 
Second, the solenoid draws under 10 amps if working correctly

The solenoid draws a steady state current of about 2 amps when operating correctly'



and, since you are trying to protect the solenoid and WIRING,

I have had no difficulty using a 10 amp fuse.

This is because the transient input current of a correctly operating solenoid is about 19 amps;
This current occurs for such a short period of time that the thermal leakage out of the fuse into the harness wires will significantly exceed the thermal input to the fuse of the transient.
Consequently it cannot heat the fuse to its blow point.

I suggest you try a 10 amp fuse and, if it blows, you go higher. However, I recommend you use a maximum of 15 amps

Leave it where you have it that is just fine.
Actually if you religiously install a slow blow fuse
a 5 amp device would be ok__Keoke


as you harness or components may be masking a corrosion problem.
 
Keoke,

I am impressed. As the late Paul Harvey would say “And now you (we) know the rest of the story”.

All the best,
Ray (64BJ8P1)
 
The holding coil may only draw 2 amps, but I believe the pull in coil draws well over 10 amps, albeit only for a fraction of a second if the linkage is properly adjusted.

I just measured the resistance of the pull in coil on a new solenoid, got about .5 ohms. So under steady state conditions it would draw about 24 amps. This could overheat wiring for sure, if the solenoid didn't move enough to transfer to the holding coil.

I think a 10A fuse would work, but only if it is slow blow, which is what was recommended by Keoke.

I am pretty sure the original wiring (at least for my BN1) does not have a separate fuse on the solenoid circuit.
 
I have used a 10 amp inline fuse for over two years now following Keoke's advice and have had no problems except initially when I had the wrong plunger that was too short to engage the switch from pull circuit to hold circuit. The blown fuse saved the solenoid until I put in the right plunger. ( I had tried to use the old plunger with the new solenoid rather than the plunger that came with the new solenoid.) My 10 amp fuse came off the shelf. I don't know if it is inherently slow blow or not.
 
HI Tim
Glad you found the malfunction and continued to use the 10 amp fuse it will provide adequate protection in this application whether it is a slow blow or not.So you are OK--Keoke
 
Back
Top