Blowing F52 Fuse After 10 Minutes of Draw, Not Instantly

[Jrath88]

Hello, Been having an issue with this fuse for quite awhile and finally had enough and looking for input.

About a year ago I was using my 12v pump to inflate a paddleboard just as I had done for years before plugged into the ciggarette lighter. NORMALLY I would do so while the truck is running, but this time I had just hit the AACC/ON button on the ignition to power the accessory outlet while I went upstairs to change and let it all do it's thing. Being Arizona in Summer I thought I would try this instead of leaving the truck run in a closed apartment garage. About 20 minutes later I got to the garage and everything was off, so I assumed the board was full and the auto-shutoff for the trucks electrical had timed out once it was full. This was not the case and either the fuse had blown and then the truck turned off or vice versa. I later realized it was the F52 fuse and not my pump, so I replaced it. Everything seemed fine and the acc port worked again, at least for the phone charger.

Ever since that day the port works fine for a phone plugged in for several hours straight on trips, but when plugging in a pump it will pop the F52 after about 10 minutes or so of draw, never instantly like I would think most fuses do. No other fuses pop or symptoms at all, and I have a bag of 20A fuses on hand now lol. I've been using the pump with alligator clips to the battery instead of the cigg plug, but the pumps are not always happy with that 14v supply going direct like that, so I'd really like to dive into this and fix it once and for all.

I appreciate all input or suggestions to try that make sense. I've got tools and multimeter and can work on it myself, just need insight on what to chase here.

TIA

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[Commodus]

Hello, Been having an issue with this fuse for quite awhile and finally had enough and looking for input.

About a year ago I was using my 12v pump to inflate a paddleboard just as I had done for years before plugged into the ciggarette lighter. NORMALLY I would do so while the truck is running, but this time I had just hit the AACC/ON button on the ignition to power the accessory outlet while I went upstairs to change and let it all do it's thing. Being Arizona in Summer I thought I would try this instead of leaving the truck run in a closed apartment garage. About 20 minutes later I got to the garage and everything was off, so I assumed the board was full and the auto-shutoff for the trucks electrical had timed out once it was full. This was not the case and either the fuse had blown and then the truck turned off or vice versa. I later realized it was the F52 fuse and not my pump, so I replaced it. Everything seemed fine and the acc port worked again, at least for the phone charger.

Ever since that day the port works fine for a phone plugged in for several hours straight on trips, but when plugging in a pump it will pop the F52 after about 10 minutes or so of draw, never instantly like I would think most fuses do. No other fuses pop or symptoms at all, and I have a bag of 20A fuses on hand now lol. I've been using the pump with alligator clips to the battery instead of the cigg plug, but the pumps are not always happy with that 14v supply going direct like that, so I'd really like to dive into this and fix it once and for all.

I appreciate all input or suggestions to try that make sense. I've got tools and multimeter and can work on it myself, just need insight on what to chase here.

TIA

Have you tried a different pump? I found that as air pumps age their amperage draw increases until they will pop a 20amp fuse

 

[Jrath88]

Have you tried a different pump? I found that as air pumps age their amperage draw increases until they will pop a 20amp fuse

I have yes. Some friends were with us a few times and we would try theirs to see if it did the same, as well as I just got a new one as well. Same result. Maybe it's the pumps themselves, but it used to be used through the ACC port with no issues dozens of times previous to this starting. Hmm

 

[Mr._Bill]

I would try something like this. The 12v power port in the cab wasn't really designed for heavy use. The 12v in the trailer wiring is always hot.

POLLAK 11-896 7-Way Power Outlet Adapter https://a.co/d/0nRgl1J

Tow Ready 118019 7-Way Cigarette Lighter Plug Adapter , black https://a.co/d/cbGg6gH

 

[PW45]

Fuses aren't necessarily designed to blow immediately. when there is a massive over-current draw they will blow very quickly but as you get closer to the fuse rating, the blow time takes will be longer. Here's an image of the blow curve for a 13amp and 3 amp fuse. Note that the higher the fault current, the faster the blow time, but for lower fault currents, it can take quite a bit longer.

 

[ShadowsPapa]

I would try something like this. The 12v power port in the cab wasn't really designed for heavy use. The 12v in the trailer wiring is always hot.

POLLAK 11-896 7-Way Power Outlet Adapter https://a.co/d/0nRgl1J

Tow Ready 118019 7-Way Cigarette Lighter Plug Adapter , black https://a.co/d/cbGg6gH

That's what I run a small compressor from (and also use to trickle charge/maintain the Jeep's batteries)

 

[Mr._Bill]

That's what I run a small compressor from (and also use to trickle charge/maintain the Jeep's batteries)

I bought one of the Pollak adapters. I was going to get the other one, but the delivery time was too long. I used it to run the travel fridge on the last work trip. The 12v port I added in the back stopped working, and I have not had time to look at it. I assume it's a similar problem to what the OP is having. The fridge is set for 36 degrees and Max Cooling. It sits in the back all day in the sun (100+ outside) when traveling. The wiring on the Nilite power port I installed was not really meant for heavy use. I'm looking at something designed for marine use to replace it.

 

[Jaxmax]

Bill perhaps the ARB fridge port and connector, it is dual use can be put in a cigarette lighter or 12 volt port ,unscrew the end and the cig lighter push pin comes off and it then has a two prong plug the fits into ARB port and then screws on tight. The ARB fridge port comes with a gasketed housing or you can take it out and put it in flush mounted. I have a couple of them in my bed one for a ARB Elements 63 fridge and another that is going to used for water pump and chargers in my build (someday). Check it out….Jack

 

[GrubbyBaja]

Not only are fuses time dependent as indicated in the above post, they are also affected by ambient temperature. A fuse may blow with a load on a hot day but then operate normally with the same load on a cold day. Could be a combination of your pump drawing a bit more load now than when it was new (i.e. bearing wear, dirt in the pump assembly, etc.) and operating in the hot ambient Arizona summer air. Put a ziplock bag of ice (well maybe double ziplocked bag) on the 52 fuse and see if it holds while using your pump. Here's yet another theory, motors are not resistive loads where current reduces when voltage reduces...it's just the opposite. Motors continue to put out the same HP rating, regardless of voltage (i.e. current rises if voltage lowers and vice versa). Since you were operating in ACC, the bus voltage was ~12V. If you typically use the pump when the engine is running, your bus voltage would be anywhere between 13.5-14.5 (typical values I see with my engine running). In the latter case, the current draw of the pump would be less with the engine running and higher with the engine not running.

 

[Jrath88]

Appreciate the input given so far. A couple of follow ups to the advice given.

Yes I know I can try a different pump or invertor or move to a cooler climate to keep the draw less with the AZ heat lol. My sticking point is that it never used to do this on even the hottest of days, it's been tried with brand new pumps of the same version that used to work just fine as well as other ones with less draw, and still the same result.

In short I'm trying to find what may have blown or partially cooked in the circuit or what to check for physical components that may have changed at the time of the vehicle timing out and shutting down to cause such an issue.

I thank you again

 

[Mr._Bill]

It could be a connection issue somewhere in the factory wiring. You would have to go end to end and check for loose, damaged, or burnt places or pins. The one day in the heat without the engine running may have been just enough to increase resistance at some point in the line that long runs now overheat and blow the fuse.

 

[kb5zcr]

Just a guess, but the longer a wire carries close to its max recommended current, the hotter it gets, and its resistance increases. This can cause the current passing thru the conductor (wire) to exceed the fuse capacity, blowing the fuse. If that pump draws 18 amps, as the wire to the lighter plug heats up over time it can exceed the 20 Amp fuse and blow.

If you have a clamp multi-meter that can measure amps you could put the Amp clamp around the positive wire on your pump (would have to separate the positive from the negative wire going to your pump) and see if the current slowly rises the longer you run it.

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