blower relay problem
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5th Gear
Joined: Feb 2012
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blower relay problem
Hi, guys and gals its me again. Could some one let me know why the blower relay keeps melting it has done some damage to the fuse box. I am getting ready to rr the fuse box and replace the relay again for the 4 time. is this common practice or is there a bigger issue. I received help with my blower problem but now it is eating up relays and now a fuse box. concerned.
Super Moderator
Joined: Jan 2011
Posts: 16,322
Likes: 88
From: Savannah Georgia
Not common issue. Year and model? And fuse.
Normally in the relay world, contacts are rated for "X" amps. Contacts usually flex ever so slightly when "made" to "scrub" off arc contamination. When connections get carbon buildup, they have a source of resistance, and Murphy's Law of un-intended physical reactions pops up. This is the famous P=I*I*R equation (electrical engineers love to eat, and pie is a favorite). Power = amps squared times resistance. So 10 amps thru a contact with 1/2 ohm will create 50 watts of heat to dissapate.
In other words, dirty connections overheat. In big switch gear it can melt important things and become a lethal hazard.
Now you could also have a situation where a previous mechanic swapped out to a larger fuse because it kept blowing. And since then, people look at that 30 amp fuse and put another one just like it back in. Please let us know which fuse number.
If you have an amp meter that will read the amp quantity pushed thru that fuse, or a clamp on amp meter, you can check to see if the (as an example) 10 amp fuse is trying to carry a 10.5 amp load. You could have a fan that is failing and drawing too much.
Normally in the relay world, contacts are rated for "X" amps. Contacts usually flex ever so slightly when "made" to "scrub" off arc contamination. When connections get carbon buildup, they have a source of resistance, and Murphy's Law of un-intended physical reactions pops up. This is the famous P=I*I*R equation (electrical engineers love to eat, and pie is a favorite). Power = amps squared times resistance. So 10 amps thru a contact with 1/2 ohm will create 50 watts of heat to dissapate.
In other words, dirty connections overheat. In big switch gear it can melt important things and become a lethal hazard.
Now you could also have a situation where a previous mechanic swapped out to a larger fuse because it kept blowing. And since then, people look at that 30 amp fuse and put another one just like it back in. Please let us know which fuse number.
If you have an amp meter that will read the amp quantity pushed thru that fuse, or a clamp on amp meter, you can check to see if the (as an example) 10 amp fuse is trying to carry a 10.5 amp load. You could have a fan that is failing and drawing too much.
Recovery Vehicle
Joined: May 2008
Posts: 811
Likes: 78
From: Howell, NJ
You don't need a new fan/fans, your pollen filters are clogged upping the amps on recirc--
You also need to cut the wires off the bottom of your fusebox and wire 2 relay pigtails directly to the blower aux. wires. If you dont, your fusebox will melt down like fukoshima.
You also need to cut the wires off the bottom of your fusebox and wire 2 relay pigtails directly to the blower aux. wires. If you dont, your fusebox will melt down like fukoshima.
Super Moderator
Joined: Jan 2011
Posts: 16,322
Likes: 88
From: Savannah Georgia
re: upping the amps on recirc--
Very true because motors draw more current under load, and max current under "locked rotor" condition (bearings siezed, etc.). Another example of Rover engineering for the ideal, rather than the real conditions.
Very true because motors draw more current under load, and max current under "locked rotor" condition (bearings siezed, etc.). Another example of Rover engineering for the ideal, rather than the real conditions.
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