Does anyone know how the RMP cluster wiring is set up. My 06 Ford F250 5.4 L RMP drops after I turn on my defrost or heating unit. It never drops in summer when I turn on my AC. Two things happen when I drive after 15 minutes of high heat. One, when I hit some bumps the needle will drop to zero. Also when I turn off the heating unit, the needle will also drop.

Where should I start to look for a lose wire under the truck or dash. Again if anyone has a diagram I could check for a lose wire or a bad ground.

One more thought. Is the the heating unit on the dash faulty?

Thanks,

 

The instrument cluster is all microprocessor controlled and is on the CAN bus. So it is not a matter of looking for a loose tach wire. You could pull the cluster and check all the ribbon connectors, and at the same time check all the grounds. But I wouldn't get too hopeful over that.

The '05-'06 is known for cluster problems. Usually it is the speedo that reads bad. I have not heard of one doing what you are describing.

 

I know that is the weird part. I fix my speedo on the back of the axle (VSS) unit. The RMP I don't understand. It only happens when I turn on the heat to warm up truck and to defrost my windows. I do not lose any power when this happens

Again, after 15 minutes of heat the needle drops. Or when I hit a big bump. Thats why I thought I had a lose wire or the heating/ac unit in the dash was faulty.

That's why I was hoping someone had a wiring diagram on the RPM. I guess it's the cluster, I just wanted to make sure before I replace it. I was hoping for a easy fix.

Thanks