40amp blown fuses

cowboy_71 · 09-16-2019, 10:11 AM

After replacing battery and connecting black to pos, ran ac all day,. This morning no power and blown fuses. How did this happen ? Replaced fuses and working now.

**Lloyd** · 09-16-2019, 12:20 PM

Boy, that's quite a puzzler cowboy.

Do you suppose it's possible those fuses get weak with age? I know it's happening to me.

But, if it's working now, that's the important thing.

cowboy_71 · 09-16-2019, 03:50 PM

So true. Do you think cause I was using a household vacuum and ac both off and on all day to clean had anything to do with it? Don’t think so cause no other fuses blown except those two 40s.

jmnsn57 · 09-16-2019, 04:48 PM

What are the 2 40A fuses supplying? If each is for one leg and your trailer is a 50A service max, then someone messed up. Any trailer/RV I am aware of has a 50A max service. Therefore 40A fuses on each side are way too high for your application - what does the mfg. want on each leg? I think you need to know which side of the panel the items in use were being operated through, if they are fused correctly - did someone boost the fuse size to correct an overloading condition - ILLEGALLY!?, and what load was applied to the entirety and each leg separately of the system - hot water, AC, Vacuum, lighting, fridge, tv, booster, etc. Good luck.

**dagst1** · 09-16-2019, 06:25 PM

Check to be sure the battery is hooked up correctly. If it is a "Fuse" and not a breaker then it is on the 12 volt side.The main line to the battery would have a high amp fuse like 40 amp.

harley · 09-17-2019, 04:01 PM

Dag is correct . 40a fuses are for battery(dc) not electric (ac) . Ac meaning electric not air conditioner. If you hook up battery incorrectly then both 40a fuses will blow along with maybe stereo and thermostat fuse. Follow black battery wire to see where it goes ...if it goes to frame it is neg.

robertwharley · 09-22-2019, 09:13 PM

Hi,
I just changed the battery in mine and had the same thing. I found out I had the wires backwards. To check, if you have a power awning, press the button to open. If it does not move try the in and if it goes out, then you know it's backwards.
Basically it's a feedback loop through the 120 to 12v inverter and if one pair of cables is backwards, then the 40 amp fuses blow. Your air worked as you were plugged into main power.

Let me know if this makes sense and helps.

Bob

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