Have you ever experienced this?

[PNWDan]

Replaced the water pump on the E30 this weekend. I now am paying close attention to the temp gage. It seems that when I turn on accessories, lights, or the heat the needle jumps up. It literally is sync with the switches. A different amount each switch

[bkslaughterhouse]

Yeah I have the same thing, it's just for a split second when you turn the key right?

[PNWDan]

No. I can switch the heater fan 1-2-3-4-5 and the needle moves up up up up and up. Almost to the 3/4 mark. Drops down when at 0

[russhixmo]

...strange, I'll have to look into that. Could be a short or possibly a resistor, I can't remember if there on the same relay or not. Check into that.

[Holland]

I remember once I cleaned my cluster cover with a microfiber and my tach jumped, the thing was sporadic for a whole week.