Can an old electric fan create excessive current pull?
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If you really want to measure amps you can make yourself one of these cheaply. Works like a dream for higher amps. Not good for low amps (like parasitic draw).
I would rather use a multimeter instead of a test light to check for faults.
I typically use my multimeter but have to be really careful because of amp limitation before I blow a meter fuse. This past year I found this circuit tester at Harbor Freight:
https://www.harborfreight.com/30-amp...ter-67724.html
I bought one since it was under 20 bucks and then used a remote-fuse-holder to which I attached a couple of multimeter probes. I can now read amps up to like 30.... or, if concerned, I can swap out the fuse in the unit itself for something lower. Just for fun, but it is digital too.... and, yes, I plan on using some soldered-on better multimeter leads.
I would rather use a multimeter instead of a test light to check for faults.
I typically use my multimeter but have to be really careful because of amp limitation before I blow a meter fuse. This past year I found this circuit tester at Harbor Freight:
https://www.harborfreight.com/30-amp...ter-67724.html
I bought one since it was under 20 bucks and then used a remote-fuse-holder to which I attached a couple of multimeter probes. I can now read amps up to like 30.... or, if concerned, I can swap out the fuse in the unit itself for something lower. Just for fun, but it is digital too.... and, yes, I plan on using some soldered-on better multimeter leads.
But it says to only run for 10 seconds max - good for quick checks, but doesn't help monitor current changes over time.
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You are on the right track. This is an opportunity for you to buy a simple and cheap 50 amp DC ammeter with shunt and mount them in a box. Then you can use it to troubleshoot this issue without a time limit on the meter. You'll use your new meter again and again in the future too. Here's a link to a 50 amp meter with shunt: 50 Amp Ammeter With Shunt
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Not joking, I have the identical fan set up. After burning out 2 relays. Frying the ground connector where the 2 plug together. And taking out 2 circuit breakers. I did some research. Found a lot of guys with twin fans ran dual relays. And or a 50 or 60 amp relay. I pull power at the starter solenoid, right off the battery cable, a couple inches at most I have a 50 amp breaker. 8 guage wire up to my relay, (in the wiper tray compartment). And 8 guage wiring to the fans and ground. Running a heavy duty 50 amp relay. No more issues. And I noticed less drop on my volt gauge when the fans kick in as well.
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All,
I've provided a detailed reply ... just waiting for the mods to approve. (I'm guessing because of the photo.)
EDIT: It has appeared above!
Thanks, guys!
EDIT: It has appeared above!
Thanks, guys!
Last edited by jacobp; Jun 1, 2020 at 09:50 PM.
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From: South Western Ontario
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From: South Western Ontario
Did you spin the fans with the engine off? You should be able to tell if the bearings are going bad.
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I have not ... that is a simple and easy idea which would provide a better feel for what's going on. I'll try tomorrow! Thanks! (My response was approved by the mods and is above.)
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Thanks for the updated diagram in your approved post!
You have a significant voltage drop across the existing wiring, perhaps even in the existing relay itself. I think you've already come around to the correct answer (two relays, two fuses, two circuits), but this should reinforce it. Be sure to check and clean all of the connections, too.
Let us know how it goes!
You have a significant voltage drop across the existing wiring, perhaps even in the existing relay itself. I think you've already come around to the correct answer (two relays, two fuses, two circuits), but this should reinforce it. Be sure to check and clean all of the connections, too.
Let us know how it goes!
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My Current Theory
I'm wondering if the current is not actually excessive, but rather :
I'm wondering if the current is not actually excessive, but rather :
- the breaker is tripping early because of engine bay heat and
- the original wires melted because of internal corrosion / age which increase the resistance and produced excessive heat.
The fuse housing melted due to high resistance and heat. Cheap terminals and too much current.
I have Bosch relays with 10awg wire in them. I used cheap relay sockets and installed some quality terminals that I crimped to the wire myself into the socket for the contact wires.
Parallel the circuits and run 2 relays and 2 breakers and separate wires. That also gives you some redundancy in that one fan will keep working even if one of the circuits or a fan motor fails.
I don't like those self resetting breakers because if you do get a short they will just keep resetting until they find the next weakest link in the system.