I had a headlight relay fail recently, causing the headlights to not cycle up and turn on. In an effort to diagnose the symptom I used a fan relay to verify the problem. Looking at the relays I noticed they both have the same specs and appear identical on the interior. Mazda has 2 different part numbers however. Headlight relay J140-67-730 for $12 and fan relay KE10-67-730 for $50 each. Other than the color and price I see no differences. Am I missing something here because it seems the headlight relays could be used in place of the fan relays saving quite a bit of money potentially.


Pins and plug are identical

Interior front

Interior back side

 

Most likely the difference in price & part # is due to the current ratings of the contacts. The E-fan circuit, and hence its relays, draws significantly more electrical current than the headlights, roughly double. IIRC the fans have a 60A fuse protecting the circuit while the headlights use a 30A fuse.

 

That would make sense but it appears that these have the same 20A rating. Now I’m wondering if my fan relays had been replaced with an underrated relay? Does anyone else have the same relays for their setup?

 

Looking at the wiring schematic, I doubt each relay sees more than 20A during normal usage. The 60A fuse supplies current to three relays. https://www.rx7club.com/3rd-generati...g-fans-462760/

I'll try to measure current through one of the relays sometime, I have a clamping current meter and I think there's access to reach the wires without taking things apart.

 

That would be interesting to verify. You make a good point about the load being separated across 3 relays. I ordered 4 headlight relays from Ray and will test them when they arrive. I’m pretty sure they will work exactly the same (terminals are also labeled the same way (comm, NO, and coil)

 

Received the new headlight relay today. The new part is sealed and in a smaller form factor. I looked up J110 but couldn’t find any info for the amp rating. Without further info I’m guessing the fan relays are not interchangeable even though the pins and connectors are identical.

New headlight relay on left, old on right