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Fan issue has me scratching my head

crash89

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I am a bit at a loss. I wired in a new fan, relay and controller. This is a Spal fan. I had just recently wired in a FlexALite fan. It worked, but didn’t pull enough air, so out with the FlexALite and in with the Spal.
Here’s where I start scratching my head.
My input is 12v on the trigger wire.
Ground is good.
Pin 87 on the relay switches correctly and has 12v when I cycle the key. As long as the fan is NOT connected.
Connect the fan, and voltage drops to zero when I cycle the key.
When I bypass the relay and connect directly from the positive side of the battery to the hot wire on the fan, the fan spins up and runs normally.
The temperature controller is out of the loop while I am testing the fan directly through the relay.
I feel like I must be missing something stupid. Anyone run into this before?
 
Bad connection, look at the terminals in the relay block.. it's not uncommon for the relay to push the terminal out of the block. If that doesn't do it try another relay. A poor connection does exactly what your describing, shows good voltage until there's a bigger draw than the bad connection can deliver.
 
I had a spare relay, and just swapped it out. Many thanks for the advice @747mopar
The problem was the same with the new relay.
It is rated for 30/40 amps and did work with the old fan.
 
I had a spare relay, and just swapped it out. Many thanks for the advice @747mopar
The problem was the same with the new relay.
It is rated for 30/40 amps and did work with the old fan.
Does the relay plug into a terminal block? If so I'd still check to make sure none of the terminals pushed out. If no luck there check all connections then look for a damaged wire. I'm assuming your using the same ground when you bypass the relay? If so that eliminates the ground. Should be an easy fix, start at the fan (with the fan running through the relay) and test for voltage and work your way back to the battery, doing this will tell you where the bad connection is.
 
Just to verify the relay is wired correctly, 86 or 85 is grounded and the other connected to whatever your using to turn it on. 30 connected to 12V source and 87 to the fan (30 & 87 can be wired the opposite with 87 being the 12V source).
Screenshot_20190502-202401_Samsung Internet.jpg
 
Thanks for all the help. I am thinking it may be a bad splice but can’t check that until tomorrow. When I meter the connection with the fan connected with a brand new relay, voltage still drops to 0. At this point, I’ll replace the 12v lead to the fan. It’s the only thing in between. Odd thing is that that wire is the one I use to bypass the relay. But that may be enough current to get through a small open in the splice.
 
Sounds like bad voltage supply circuit to relay. If you run directly from the battery to relay B+ terminal (30), and fan works fine, then you will know your B+ supply circuit is at fault.
 
Have you ever felt like a complete idiot? Troubleshooting 101. Check the weakest link first. The new fan draws more power than the old. Replaced fuse. Ops check good. It read 12v with a blown fuse because the fuse had an LED in it to let my dumb *** know it was blown. It was covered and I didn’t look. That also explains why it wasn’t showing an open when I ohm’d out the power lead. Thanks for all the help guys.
 
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