Mazda temp gauge, overheating, sending unit, etc. issues...

Truck is a 87 B2000 w/ original motor that was rebuilt about 30k miles ago. It is bodied and bagged. Motor has a pacesetter header, weber carb, and electric fans.

The gauge reads hot, real hot. On my way to Dropzone it was pegged all the way to the H but was runnin great.

I don't doubt the motor runs hot but just how hot is the question.

If I start it and let it idle within a couple minutes its 3/4 of the way up the gauge and by the time I hit the end of my driveway its most the way up.

We've installed a new water pump, thermostat, temp sending unit, and even tried another identical tach gauge cluster.

With the temp sending unit wire unplugged and testing the resistance at the sending unit I have no reading. As the truck warms up the resistance drops to about 20.9 ohms where it pretty much stays. At an idle it never drops more than that.

Now here is where I'm not sure how things should act. With the key off I can test resistance at the temp gauge wire at the sending unit with it unplugged and its about 100 ohms. If I unplug the gauges I get no reading on the wire.

The electric fan is moving more than enough air and I believe the radiator to be in good working order. I don't believe the truck is overheating but I really want the gauge to work properly just in case.

Does anyone know what the ohm reading of the sending unit should be at running temp?

I'm gonna buy a laser temp gun so I can test the temps and see whats goin on.

i dont trust the factory guages i went with after market mechanicals for 40 bucks

Edited: 8/12/2007 11:46:28 PM by Twistedimg

I don't want to run mechanical gauges or even aftermarket electric gauges cause I don't want extra gauges and really just want the factory one to work.

I'd really doubt 2 gauge clusters are wrong, so try replacing the temp sensor. The fans may be moving plenty of air too, but if the radiator core is plugged up inside where you cant see it will overheat.

I've already replaced the temp sensor and the radiator is not a factor since the gauge shows hot before the thermostat even opens.

What I would really love is someone with a B2000 to unplug their temp sensor wire, run the truck to normal temp, and give me the resistance rating they have between the thermostat housing and tip of the temp sending unit. Seems that no where online can you find this for a Mazda.