perryrace

L33 - 99 Miata conversion

I have installed a Race Paq dash (UDX steet version) in my conversion project and have run into an issue I have been unable to find a cure for.

Specifics:
UDX temp sensor (single wire 5v thermo type) is installed in the passanger side head (rear port).

Running a Griffin radiator, shroud with twin 14" fans

When the engine is at idle I see 14.4 volts and temps climb to 190 F. Then the fans kick in. When the fans turn on voltage drops to 13.3V and the water temp then shows 270 F and fluctuates. When the fans turn off the temp shows an accurate (lower) reading again.

I have swaped out the temp sensor, same issue
I have checked all grounds etc - no issue found

Fans are wired via an after market conversion harness with dual relays for the fans (1 power source per fan via a relay per fan)

It seems the input voltage variance (14.4 - 13.3) is the issue but do not know how to solve this one. Any ideas much appreciated.

Mark