need help with water temp guage following Motronic conv

pappentl · Post by **pappentl** » Fri Aug 22, 2014 6:45 pm

I'm finishing a conversion of an '80 e12 from L-jet to Motronic 1.0 from an '85 535i using an M30B34 w/o cat. It's all up and running, even the accelerator cable, with the exception of the tach and water temp gauge. I've seen info on running the wire for the tach, but has anyone used this system and gotten the water temp gauge to work? Do I need to install the e12 sensor somewhere or can I use the e28 two-wire sensor? TIA.

wkohler · Post by **wkohler** » Sat Aug 23, 2014 2:54 am

E28s used just a single wire sensor for the temperature gauge. E23s and E24s had a two-wire sensor, but the second wire was just for a warning light which was past the red portion on the gauge.

Don't have an answer on the tach issue.

pappentl · Post by **pappentl** » Sat Aug 23, 2014 3:11 pm

the e28 temp sensor has two pins, I haven't traced them through the wiring diagrams to see where they both go. One or both go to the ECU, and there is a brn/wh wire at the harness connector that should power the gauge, but I don't think the e12 and e28 gauges take the same input, any idea if they gauges are the same or different? TIA.

tom

-----Original Message-----
From: wkohler <christopher.kohler@gmail.com>
To: tech_forum <tech_forum@firstfives.org>
Sent: Sat, Aug 23, 2014 3:54 am
Subject: Re: need help with water temp guage following Motronic conv

#AOLMsgPart_1_4652b3ed-50b0-4973-a5fe-bf38b24b462d td{color: black;} E28s used just a single wire sensor for the temperature gauge. E23s and E24s had a two-wire sensor, but the second wire was just for a warning light which was past the red portion on the gauge.

Don't have an answer on the tach issue.

Christopher Kohler
07/80 M535i 5-Speed Polaris/Marineblau
07/75 530i 5-Speed Golf/Schwarz

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Mike W. · Post by **Mike W.** » Sun Aug 24, 2014 5:42 pm

pappentl wrote:the e28 temp sensor has two pins, I haven't traced them through the wiring diagrams to see where they both go. One or both go to the ECU, and there is a brn/wh wire at the harness connector that should power the gauge, but I don't think the e12 and e28 gauges take the same input, any idea if they gauges are the same or different? TIA.

tom

Not only are the sensors compatible, they are the same. If you have one with two prongs sticking up, one large and one small, the small one is for a warning light used on Es 23 and 24, but not E28s. They are still compatible, just ignore the small prong.

pappentl · Post by **pappentl** » Sun Aug 24, 2014 6:24 pm

thanks.

-----Original Message-----
From: Mike W <mw999@sonic.net>
To: tech_forum <tech_forum@firstfives.org>
Sent: Sun, Aug 24, 2014 6:42 pm
Subject: Re: need help with water temp guage following Motronic conv

#AOLMsgPart_1_4467e329-03f7-4ddf-9e10-1dcef18a4fe0 td{color: black;} pappentl wrote: the e28 temp sensor has two pins, I haven't traced them through the wiring diagrams to see where they both go. One or both go to the ECU, and there is a brn/wh wire at the harness connector that should power the gauge, but I don't think the e12 and e28 gauges take the same input, any idea if they gauges are the same or different? TIA.

tom

Not only are the sensors compatible, they are the same. If you have one with two prongs sticking up, one large and one small, the small one is for a warning light used on Es 23 and 24, but not E28s. They are still compatible, just ignore the small prong.

Mike W.

1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter

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