PCM is not grounding fans properly

[jrpontiac]

I posted this in the electrical forum as well.

I am working of the relay setup for my engine fans on my LS conversion. I got a dual fan setup with each fan triggered by a relay that is activated by the engine PCM. Each fan has it's own relay. The PCM activates the fan relay by triggering the ground to the relay. My problem is that when the pcm triggers the fan (about 190degrees) that fan only runs 1/2 speed, maybe less. The relay is also rapidly clicking, both relays do this. When I bypass the PCM ground with a wire clipped to a solid ground the fans run at 100% and the relays don't click.

So I assuming I have a grounding issue, my problem is I don't know how to improve the ground since it terminates somewhere in the PCM.

The fans have their own ground, which I believe is adequate because when I activate the relay by grounding it to the neg battery post the fans work great. When I let the relay be activated by the pcm ground switch the fans don't work so great.


Any suggestions?