Weird issue with factory gauges after engine install

[smooth]

So, as some may know, I put I 93 serpentine engine in my 92 that had a V belt set-up. So, I have been having temperature issues, the trucks been running hot on the factory gauge. It would get between M and A. Then I noticed when I put the truck in reverse the gauge came down between the N and the O, where the truck used to run at before I had to swap the engine. And I I also noticed the factory oil pressure gauge would go down, which is a relief, because it was running way higher then I remember. Also, I thought the factory oil pressure gauge is just a dummy gauge.
Anyways, I mention the belts because the wiring for my old alternator is different then the wiring necessary for the alternator for the serpentine set up. So, I tried to figure out the wiring and finally got it to produce 12+ volts and show up on the factory gauge, but I'm thinking that's where my issue us coming from.
Anyone have this happen? Any suggestions on how to wire it correctly? Beyond the main wire, it's going from a three wire from the 92 to a two wire off the 93 alternator.
Any help?

MoMo

 

[Goofyexponent]

It would get between M and A. Then I noticed when I put the truck in reverse the gauge came down between the N and the O, where the truck used to run at before I had to swap the engine. And I I also noticed the factory oil pressure gauge would go down, which is a relief, because it was running way higher then I remember. Also, I thought the factory oil pressure gauge is just a dummy gauge.
MoMo

I wouldn't trust the factory gauges if my life depended on them. I put a set of full mechanical gauges in the truck for about $30. It's just a cheapy set, but anything is better than factory.

 

[smooth]

I fully agree, I've put oil pressure, water temp, and tranny temp in my other two rigs. But I just dropped some serious coin on boost, pyro, and tranny temp for this rig and was hoping to have the factory water temp work for a while.
Ultimately, you are correct, I even have a cheap mechanical water temp gauge I can thrown on, but I am curious as to what's causing my problem.
also, I got it backwards, the 92 had two wires, the 93 has three wires. I think my problem lies with the fact that one wire was suppose to go directly to the battery and I hooked it up to themain wire coming off the alternator. What I can't fgure out, is why throwing it in reverse fixes it?

MoMo