Temp Gauge Inop -Still

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geordi
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Temp Gauge Inop -Still

Post by geordi »

Cannot get the temperature gauge needle to operate on the dash. After posting on the M30B35 swap thread, I ordered new Cooling Temp Sensor and new Coolant Temp Sending unit. Installed both today and the temp gauge is still inop. Installed the old US cluster that came with the 525i and the needle did not move. Re-installed the rebuilt Euro cluster from Ivo and the needle does not move with a warm engine.

Opened the Bentley's again and repeated the test in the Cooling section 10.3 (figure 3.6). The temp gauge does not move with the old US instrument cluster. I'm unsure of its reliability because I purchased the 525i without an engine. Never knew if the gauge was operable or not.

Re-installed the rebuilt Euro instrument cluster and repeated same test. The needle does move, just a slight bump off the 10'oclock mark. Is this considered making the needle move or should the test move the needle to the 1100 to 1:00 o'clock position with a warm engine?

Looking at the connector for the sending unit on the harness. I see brown/yellow and brown/violet wires. I also see they terminate at the blue serial plug into the back of the instrument cluster. Now I'm wondering if the wiring is damaged leaving an open circuit. I follow the br/yl & br/vt as far as I cannot find any damaged wires.

Only thing I see out of the ordinary is a ground wire that has been soldered under the dash. See pic.

I downloaded the ETM for the 635csi and tried to make sense of what I'm reading. Still trying to digest it. Since i have a e24 6er harness, I guess i should be using 635csi ETM, correct?

For clarification, here is what I'm working with:
- 1985 525i
- M30b35 swap with an 88' e24 6er harness.
- rebuilt Euro instrument cluster
- installed new sensor and sending unit. Part numbers 13621709966 & 12621710511.

Suggestions for the next step to get this gauge working would be appreciated.
Thanks,
geo

Image

My two connections for instrument cluster.


Image

Red arrow points to soldered brown wire to grounding nut of column.
Last edited by geordi on Jun 15, 2015 12:33 AM, edited 1 time in total.

cek
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Re: Temp Gauge Inop -Still

Post by cek »

On the 87-88 E28 ETM (which is all I have) I see BR/VI going to the gauge and BR/YL is for the "CHECK" indicator:

Image

One thing you can do is do continuity test on the wire. You'll need a long extension for your ohm-meter. I have a collection of wires with alligator clips on each end that I use for this.

That would at least rule out the harness.

cek
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Re: Temp Gauge Inop -Still

Post by cek »

George, you see this? http://www.mye28.com/viewtopic.php?t=34049 Dunno if it will help, but I just came across it looking to see if there was a FAQ on the various E28 clusters.

ovide
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Re: Temp Gauge Inop -Still

Post by ovide »

The fastest 'quick-and-dirty' test there is, is to pull of the single wire that goes to the temp sending unit and ground it by pressing it to the engine block.

The needle should go all the way to maximum overheat, if that works, you can rule out the wiring and the cluster.

You mention it has an '88 E24 harness, that could make a difference as I'm not sure how it hooks up to the fusebox. Pics?

geordi
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Re: Temp Gauge Inop -Still

Post by geordi »

cek wrote:George, you see this? http://www.mye28.com/viewtopic.php?t=34049 Dunno if it will help, but I just came across it looking to see if there was a FAQ on the various E28 clusters.
Thanks… how did I miss this on the search!

geordi
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Re: Temp Gauge Inop -Still

Post by geordi »

Thanks CEK. I think I know what you mean about the extension w/alligator clips, but if you can shoot me a photo of your set up tomorrow it would be much appreciated. Here is the link from the 635csi ETM.
http://wedophones.com/Manuals/BMW/1988% ... Manual.pdf 6210-2

So if I'm reading this correctly, on the 635csi, its 20 gauge br/vi wire from the sender unit to the C101 connector, pin 4. Changes to a br/rd to the C1 connector on the back of the cluster.

The e28 is br/wt to the c101 then br/vi to the C1 connector on the back of the cluster.

Am I reading this correctly?

cek
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Re: Temp Gauge Inop -Still

Post by cek »

geordi wrote:Thanks CEK. I think I know what you mean about the extension w/alligator clips, but if you can shoot me a photo of your set up tomorrow it would be much appreciated.
These: http://www.amazon.com/Elenco-TL-6-Stand ... B0002JJU28
Image
geordi wrote:Here is the link from the 635csi ETM.
http://wedophones.com/Manuals/BMW/1988% ... Manual.pdf 6210-2

So if I'm reading this correctly, on the 635csi, its 20 gauge br/vi wire from the sender unit to the C101 connector, pin 4. Changes to a br/rd to the C1 connector on the back of the cluster.

The e28 is br/wt to the c101 then br/vi to the C1 connector on the back of the cluster.

Am I reading this correctly?
Image

I don't think you are. You didn't change anything from the C101 to the cluster. The wiring harness you put in with your M30B35 'stop's at the C101 (which is where it plugs into the fuse box). From there into the car it's pure E28 and the E24 ETM doesn't help.

So the diagram above is useless ABOVE the C101 line. Below that, yes the .5 BR/VI should plug into pin 4 on the C101.

You want the wire that comes from the temp sender to go to pin 4 on the C101.

You can easily test if it's connected by unplugging C101, poking your ohm-meter's probe into pin 4 (the pins are labeled, but very hard to see) and the other end on the connector that plugs onto the temp sender.

waynet1
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Re: Temp Gauge Inop -Still

Post by waynet1 »

cek wrote:
geordi wrote:Thanks CEK. I think I know what you mean about the extension w/alligator clips, but if you can shoot me a photo of your set up tomorrow it would be much appreciated.

You can easily test if it's connected by unplugging C101, poking your ohm-meter's probe into pin 4 (the pins are labeled, but very hard to see) and the other end on the connector that plugs onto the temp sender.
Look in the ETM under "Connector Views", it shows the pin layout from the wiring face.

Mike W.
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Re: Temp Gauge Inop -Still

Post by Mike W. »

E28s that I've seen didn't have a high coolant temp switch, but E23s and E24s did, so you should have just a single terminal temp sending unit with a single wire. Ohm out the sending unit and try grounding the wire to it, it would be the one with a 1/4" tab.

tschultz
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Re: Temp Gauge Inop -Still

Post by tschultz »

Interested to hear your problem George.

I will be tracking the same problem on my 633. I swapped in an engine from an E28, and the gauge worked when i pulled the engine! I think for me this means it's an issue with the harness or the pinout from the harness to the C101 connector.

Let us know what you find!

Mike W.
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Re: Temp Gauge Inop -Still

Post by Mike W. »

FWIW, showing how things can change between submodels, 524td's have a rather different pinout at the C101 plug than 535s. So an E24 definitely could.

On the other hand, I'd reuse the engine harness that came with the car, the FI harness is a different matter if you're changing engine management, but usually the engine side would work and be correct.

geordi
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Re: Temp Gauge Inop -Still

Post by geordi »

Thanks for the assist everyone :up:

Image

Occam's Razor: the simplest answer is often correct. At the suggestion of another member, I made a jumper to the other connection. A similar issue occurred with his swap.

Image

It works! :D

nharperc
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Re: Temp Gauge Inop -Still

Post by nharperc »

My 1988 528e cluster has a dead temp gauge and tach.
Technically speaking the temp gauge isn't dead, it's intermittent at best.

I just replaced the temp sender but there's no change.
Tomorrow I'll test the harness continuity because I seriously suspect the elbow in the first 3" of the sender wire.

-Neil

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