I have an '89 745Ti turbo+ M46 128K.

I have a set of oil temp and pressure gauges with senders that I found in the PnP last year. I've been itchin' to put them in for the last couple of months.

Yesterday, I was bored and I really didn't have any car repairs I wanted to tackle. So I decided I would install the gauges. I went to the local auto parts store and got the necessary wiring and connectors to install them professionally.

I first want to install the oil pressure sender from an '84 744GLE. I thought that the original sender/switch was a 22 mm. I couldn't get a socket over it and I ended up removing the power steering pump assembly just to reach the switch. I then found out that it was 24mm and my impact sockets fit. Finally an 1 1/2 hr later the switch was out. I then installed the VDO sender using a 19mm open end wrench at 15 deg. swings.

The oil pan sender was installed during last oil change (It leaks)for the temp gauge.

I then pulled the instrument cluster. Took it inside and hooked up the blue/red (pos)wires of both new gauges to the red wire going from the previous voltmeter gauge on the pc board. I next hooked up the black wires (grnd)to the black of the voltmeter spot on the pc board. I used matching colored wire for each corresponding sender. Green for the pressure and yellow for the temp.

I had to loosen 2 screws on the pc board to get the upper right gauge in. More on this later.

I installed the cluster; hooking up the wires was a PITA! Started her and....

Oil temp didn't register which is ok but oil pressure pegged. I checked the wire going to the sender and made sure that the green wire was on the correct post. It was, switched them and no change. Then I grounded the green wire to the battery and still no change. So it must be the gauge.

I let the car idle for a while and let the oil temp gradually goes up to 210F. Ok that appears to be working fine.

I go to turn on my lights and there is no instrument or interior panel lights.
It was getting late and I was cold from working outside for the last 3 hrs. I decided to finish it today.

Meanwhile last night I thought about why the gauge was pegged and there was no instrument lights. I then remembered the 2 screws that I had loosen and I don't remember tightening them back down. The instrument lights feed off of those 2 screws. The red wire and the blue one.

Today, I pulled the cluster back out and checked the wires/contacts going to the sender from the oil pressure gauge. I then tighten the 2 screws down.

I figured I had solved the instrument lighting problem and I would have to replace resistors in the oil pressure gauge. I re-installed the cluster and fired her up and.....

SRS light was on, no working fuel gauge, oil temp now pegged. Oil pressure still pegged.

I looked up from underneath and saw the connector on the driver's side was off. I reached up and re-connected it. The oil temp, fuel gauge works and the SRS light was off. Great, making progress. Sort of. I turned on my lights and still no interior panel lights. Checked intensity control by wiper switch and it is turned all the way clock wise (brightest.) I checked all of the fuses and they are good.

I took the car for a spin to make sure the speedo and all of the other gauges except the oil pressure work properly. Lo and behold the gauge starts working a few blocks later. Later on it pegs for a while.

I think there is a loose connection somewhere inside the gauge itself I will have to check. I think I burned out the brightness control for the panel.

I will have to pull the cluster for a third time and replace the brightness control and maybe try and fix the oil pressure gauge. I will be running seperate pos and grnds for the gauges to make sure that they aren't influencing the voltage/amperage on the pc board. Any thoughts?

Does anyone have/know where I can get a wiring diagram for the cluster for an '89 745 M46 and CC.