Tongue Jack Blowing Fuses

[pdlarson]

Not sure if this belongs in Travel Trailers or Tech but here goes: My electric tongue jack keeps blowing 30 amp fuses. I don't recall this happening for the first year or two I had it but suddenly earlier this year I started having trouble. There is a manual override but it is very difficult to crank. I have a supply of fuses that has helped me out of a jam but I'd be curious to know why this is happening in the first place. I don't see anywhere where it says what size fuse to use, 30A is what it came with new so that is what I have been using. I know that in general the recommendation is to not insert a higher rated fuse and to inspect everything because fuses blowing could be a sign of other trouble. The problem is that I can't seem to find anything wrong. This typically happens if the jack is over-extended in either direction (not on purpose or for a long time but you never know when it will stop until it stops) or when just starting to lift the tongue. Any ideas?

Thanks!

[Ashley032386]

I have had my camper for 4 years now and have never had a problem. However we were just camping and when we were hooking up to leave and pushed the button to lower the jack the fuse blew. We replaced the fuse and it happened within 2 seconds of hitting the lowering button. Replaced with last of fuses we had and did exact same thing. So we had to use the manual crank to get it down and also then when we got home same thing and had to crank up with the manual tool. 

Any ideas what could be causing this? It has never happened before.

[way2roll]

You are responding to a topic that is 11 years old. You might get more help if you started a new topic with your question. 

[Ashley032386]

Thank you. I am new so was not sure. I started new conversation. I appreciate your message back.

[camperpaul]

One more thing that can cause the fuse to blow is:

When the jack reaches the end of its travel, the motor stalls and draws enough current to blow the fuse.

A properly designed jack will have "limit switches" to prevent this.

[pdlarson]

Thanks for all the comments everyone. It's cold now but I'll look into lubrication and also the Bussmann "cb221-30" circuit breaker which I believe is the correct type for my regular size fuse.

It is hard to answer if the fuse only blows going up as it has happened after lowering the tongue but was it blown after lowering fully to the end of travel or after attempting to start to raise the tongue? I'm not sure. I can do some testing to find out but at this point I think the jack will get lubed, breaker installed and that will be it.

[MRBIG1]

My son-in-law’s brand new trailer was also blowing the electric tongue jack 30 amp fuse, we replaced the fuse with a 12 volt DC, 30 amp auto resetting circuit breaker. Problem solved, the tongue jack never trips the circuit breaker.


Link to circuit breaker we used[url=]

[PaulJ2]

Yes that is correct. Power in watts is P=EI. 6 volts at 300 amp is 1800 watts.
12 volts at 150 amp is 1800 watts.

[RJsfishin]

Is that why identical V-8 engines starting draw twice as many amps on a 6v system, as a 12v system ? Amp meters don't lie !

[PaulJ2]

Ivylog wrote:
P=EI is a fairly simple formula. Doubt E knows the difference between AC and DC volts.

No but the motor does. Ac motors are frequency dependent and try to keep their speed with the frequency and thus draw more current if the voltage drops. DC motors are variable speed with voltage.
Voltage drops and the current drops.

[Ivylog]

P=EI is a fairly simple formula. Doubt E knows the difference between AC and DC volts.

[Mandalay_Parr]

RJsfishin wrote:
Fuses blow because the amperage going thru it is more than the fuse is rated for. (Duh?) Like we dint know that 🙂
Ok, why is the amperage too hi ?
Besides all the reasons below, remember, when voltage goes down, amperage goes up. So, check the voltage at the jack while operating the jack. It may just be a problem of low voltage, either from a bad connection, or a battery that is not what it used to be. Load test the battery !

I don't believe this is true for DC motors. Voltage down, current down.

[ICamel]

Sounds like it is designed that way, which happens to me when I overextend the front jacks on my 5r (like Duck describes in his post) in either direction. It is possible in the 1st year that you never overextended the jack. I solved that by changing the 30A blowable fuse to a 30A Auto Reset Circuit Breaker. It fits in the fuse holder and resets itself after detecting a fault. You can buy at auto parts stores, or on Amazon.com
"Bussmann (BP/CB211-30-RP) 30 Amp Type-I ATM Mini Circuit Breaker"

pdlarson wrote:
This typically happens if the jack is over-extended in either direction (not on purpose or for a long time but you never know when it will stop until it stops) or when just starting to lift the tongue. Any ideas?

[beemerphile1]

Does it only pop the fuse when lifting the tongue or does it also pop the fuse when unloaded?

[ScottG]

I would lube it and hope that solves the problem but excess current draw is also a sign of a worn out motor, especially when it never did it before.