I blew a fuse yesterday for fan2 and was going to replace. when I started looking at the relays, I noticed that the fan1 relay had a problem. I would like to here from you Electrical Engineers about this.

Schematic for Fan1 relay


Relay showing the hit that pin 87 took:


Relay connector topside:


Relay connector bottomside showing burnt wire:


What happened to cause this? Could this have been a power spike from the fan? What??

Why would this have burned the installation, and I assume the wire, and not have blown a the 20amp fuse? (Schematic stating 30amp fuse is incorrect.) This is a 12 gauge GXL wire.

Thanks for looking and listening.

 

I have been through 3 relays in my Nelson harness that look like that. Not sure what causes it, but they have definitely burned up. I have never blown a fuse.

 

If your running Bosch relays, try going to another brand. I used to use a ton of Bosch relays but kept having issues with them never being capable of holding the load ratings they were listed for. I then switched over to using the old Potter & Brumfield / now Tyco relays and haven't had a single problem on any of our race cars.

 

My first guesses would either be an inferior relay that can't handle the load, or a shorted fan motor causing excessive current flow in that ciruit.

 

They are Bosch relays I'm using. I noticed after testing the new wiring the relays get very hot to the touch.

Maybe I might try some Tyco's

 

From the pictures you posted I would venture to say that there was a loose connection on that particular hot leg of the relay, It was probably crimped improperly. A loose or poor connection will cause heating and the damage which you have on your harness. (i.e. burnt insulation melted relay).
I would make sure that you replace that entire length of burnt wire,

I have some good working experience with electricity (shade tree electrician). At 12 volts DC #12 wire (which is what most of our harnesses are made of) is only good for 20 amps at a maximum distance of 6.6 feet. I have yet to put my meter on my fan harness to check for how many amps its pulling at startup but I would venture to say its in the 40-50 range. One previous poster stated 70 amps at startup but I wont know until i check for myself and I am not discrediting him it just seems like an awfully high number for the size of the motors being used.

This momentary spike in current whether it be 40 or 70 amps is not necessarily going to burn up the wire or blow the relay even though it is a 20 amp or 30 amp fuse because it takes time to for the relay to trip or if the relay is improperly sized the wire to burn up, this time is determined by the current and load being carried on the wire. As I was stating the wiring only experiences this much current for a matter of seconds while the fan is ramping up speed then settles back down to a more acceptable 5-10amps.

All that being said I still have my reservations on the size of wire being used for these harnesses, there seems to be several people having problems with them. I will do some more checking and get back on this.

It is possible that you could have a bad motor or just keep getting bad relays however I would double check that all of your connections are clean and tight. If possible and if they are not already solder over all of your wire junctions, this will ensure that you have the best possible joints on your harness. Eliminate all of the possible weak areas and it will help you narrow down the problem causing the failures.

Sorry for being so long winded. Hope this helps a little.

 

im having the same porblem, i have burned upi two in like 3 months. My relays are 30 amp, so are my fuse. I 'm thinking about getting like a 40 amp and see what happend.

 

Don't get me wrong - there was nothing wrong with the relays, they were still in working order. I just want to know about the excessive heat.

 

i run dual fuse holders and relays for my fan setup, but i run the twin ls1 fans together, i disconnect 1 in the winter time

 

doesn't look like a relay problem to me. resistance=heat, thats what happens when you have a bad connection. probably a bad crimp or a loose terminal.