90 Tach cluster into 87
 

My tow truck doesn't have a tach but I have a cluster from a 90 Bronco. 87 still uses the real oil pressure sender, not the on/off switch like the later ones IIRC. Do I have to change anything on the cluster before putting it in?

Yes, you need to do 1 thing. On the back of the oil gauge on the back of the cluster, there is a resistor in the oil pressure gauge circuit. Solder in a wire to bypass this resistor. That will make it function like a gauge again. There are a few threads floating around this. I have one saved on my computer, but I'm not there at the moment.

Here is the one I was thinking of. This makes it clear as a bell!
https://www.ford-trucks.com/forums/1...tructions.html

Ok, swapped the cluster in and no tach, no oil pressure...

I should mention this is a cab and chassis truck. Not sure if that makes a difference. The cluster was working fine when I took it out of a 90 Bronco I parted out.

Ideas?

And yes, I bypassed the resistor. Just with a wire twisted on for now till I can get my soldering iron out, but that shouldn't matter.

It was a gasser, right? Gas cluster won't work in a diesel. Sorry I forgot to mention that!

Both gassers. 351 Bonc and 460 C&C

Do the temp and volt gauge work? Try grounding out the oil gauge sender wire out at the engine.It should go to high. If it does, you may need to get the sender mentioned in the linked thread. If it doesn't, there may be a problem with the connections on the cluster. If it only goes half way, the twisty wire thingy didn't work.

Volt and temp gauge work. It's dark so I don't know what sender is in it, the real one or a switch. I do know the temp gauge with the original cluster would jump around while driving, it would peg on H randomly. I was going to replace the sender and see what that did.

Either type of sender would make it move some, unless it was bad. Try grounding it out tomorrow and see what happens.