Can an aftermarket head unit cause gauges not to work

[Appleseason]

So I checked the SI batteries and they seem to be in good working order.

I guess the only thing to do is to try to find someone in the Seattle area to barrow their gauge cluster.

[IceWhite]

Until you find another cluster, you may want to check out yours. You can remove it and open it up carefully to start inspecting.

The brown/violet wire enters the cluster at the blue plug(C1) pin 26. Check continuity from the pin in the plug to where it is soldered to the cluster board. Then start tracing from that solder joint until it goes to the temp gauge. Most likely it is one of the solder joints.

[Appleseason]

Until you find another cluster, you may want to check out yours. You can remove it and open it up carefully to start inspecting.

The brown/violet wire enters the cluster at the blue plug(C1) pin 26. Check continuity from the pin in the plug to where it is soldered to the cluster board. Then start tracing from that solder joint until it goes to the temp gauge. Most likely it is one of the solder joints.

Wait, did you say pin 26, I could swear that it is going into the wrong pin. Let me double check.

Just to be certain, pin 26 is on the top row, with the plug wires going right, right?

[IceWhite]

As per post 10 quoted below for you.

Ok, so as TimeMachinE30 stated, you need to trace the wire. The wire in question is usually a Brown/Violet (or purple) wire that starts from your brown temp sender. It then goes through the C191 Connector (Pin 4) then to C101 connector (Pin 4) then to the cluster Blue plug (Pin 26). This info is correct for my car which is a 1990 model 325i and with a motometer cluster. Download the ETM for your car and confirm the wire color and pin positions all the way from the sender to your gauge. If yours are the same, you can now check for continuity along the wire as you can see there are a lot of connectors that can be corroded and cause the connection to be broken.

You can download them here: http://wedophones.com/BMWManualsLead.htm

[Gregs///M]

So I checked the SI batteries and they seem to be in good working order.

I guess the only thing to do is to try to find someone in the Seattle area to barrow their gauge cluster.

What makes you think they are in good working order? Most 30 year old batteries, on the SI board, should be considered dead. IN addition, broken electrical traces are very common on the E30 cluster. See our technical articles page at bavrest.com for explanation of this damage. It will no doubt cause your temp gauge to not work.

Lastly, unlike what programa, E30_dad, and most everyone else on the internet says, changing the batteries on the SI board rarely fixes the board. There are about 15-20 transistors and voltage regulators that must also be changed.

Ever hear people talk about how you smack the cluster to get it to work? This smacking jogs the stuck transistors. They must be replaced also. Dead transistors will no doubt cause temp gauge failure and more.

[Gregs///M]

Additionally, the only way to know for sure if your lithium batteries are good or not is to remove them from the SI board and perform a current draw test. The batteries can read 3V still but have 0-100ma draw on them. They should have around 800-1000ma draw.

[Appleseason]

As per post 10 quoted below for you.



You can download them here: http://wedophones.com/BMWManualsLead.htm

OK,

I double checked and there is continuity, sorry for the confusion.

[Appleseason]

What makes you think they are in good working order? Most 30 year old batteries, on the SI board, should be considered dead. IN addition, broken electrical traces are very common on the E30 cluster. See our technical articles page at bavrest.com for explanation of this damage. It will no doubt cause your temp gauge to not work.

Lastly, unlike what programa, E30_dad, and most everyone else on the internet says, changing the batteries on the SI board rarely fixes the board. There are about 15-20 transistors and voltage regulators that must also be changed.

Ever hear people talk about how you smack the cluster to get it to work? This smacking jogs the stuck transistors. They must be replaced also. Dead transistors will no doubt cause temp gauge failure and more.

Additionally, the only way to know for sure if your lithium batteries are good or not is to remove them from the SI board and perform a current draw test. The batteries can read 3V still but have 0-100ma draw on them. They should have around 800-1000ma draw.

Thanks for the info, my main concern is that it might not be a gauge problem, until I swap one to double check I can't rule that out. Once that is checked and the gauge is still bad, then my only real option is to send it to you to get refurbished.

[Appleseason]

ISSUE RESOLVED

For whatever reason, the previous owner switched 2 wires in the engine plug. There is no way to describe how it made me feel. At least now everything is working.

[IceWhite]

Which engine plug are you referring to?

[Appleseason]

Which engine plug are you referring to?

The body plug, it had a few pins out of place.