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Old 01-07-2004, 07:53 PM   #1
stimpy
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Default WRX Thermometer and Older Gauge Clusters

I know there are a couple people who have reported this problem, so I'll post this up and see if we can get ourselves a solution.

Background:
1996 Impreza L (originally 2.2L) now with 2003 Impreza WRX 2.0L
2003 EJ20 sensors
1996 Gauge cluster
The thermometer and engine coolant temperature sensor were combined into one sensor at some point and apparantly the signal was also changed.

Problem:
As the car is warming up, the temperature gauge on the gauge cluster can be seen moving up the scale rapidly. Once warm, the temperature gauge is pegged at the very top.

I searched all the Factory Service Manuals and was unable to find any specifications as to the output voltages produced by the thermometer or expected by the gauge cluster. Since I can see the gauge climbing rapidly, I would venture a guess that the scaling is just wrong and needs to be throttled down. Anybody have any thoughts or solutions?

-Jon
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Last edited by stimpy; 01-20-2004 at 01:13 AM.
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Old 01-08-2004, 12:04 PM   #2
Geek Guy
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Does the car run normally? Is the cluster temperature sensor signal the same one that gets fed to the ECU?

What I've seen with our rally car is if the two sensor wires short together, then the computer, cluster will read HOT and affect the operation of the car.
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Old 01-08-2004, 01:35 PM   #3
stimpy
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The car runs normally. No Diagnostic Trouble Codes are thrown relating to the engine coolant temp or the thermometer.

The cluster temperature sensor signal is not the same one as the one being sent to the Engine Control Unit. The EJ20 has a single physical sensor that contains both the engine coolant temp sensor and the thermometer. However, they send seperate signals along seperate wires. The engine coolant temp sensor is fed directly into the Engine Control Unit and the thermometer signal is fed directly into the gauge cluster.

This is a known problem with the engine swaps into the older cars so I don't think it is simply a matter of crossed wires. I'd love to be proved wrong though.

-Jon

Last edited by stimpy; 01-20-2004 at 01:13 AM.
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Old 01-08-2004, 08:08 PM   #4
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Yeah I have this problem with my swap as does another friend who has done this swap. I was wondering what the average running temp of the Impreza L is as well as that of the WRX...I think it may be due simply to the hotter running engine or just a difference in resistance between the new sensor and what the old one was.
Take it easy, Micah
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Old 01-19-2004, 03:07 PM   #5
stimpy
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Silly me. The temperature gauge grounds clear down through the Bulkhead Wiring Harness and terminating with a ground in the Engine Wiring Harness. I had initially thought I could disregard that wire because it wasn't clearly labeled as a ground (it is a Red/Green wire). Anyhow, I soldered in the ground and my temp gauge works wonderfully. It now sits dead even, 1/2 way up the gauge.

Looks like my assertions that the signal changed were simply unfounded and wrong.

-Jon

Last edited by stimpy; 01-20-2004 at 01:14 AM.
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Old 01-19-2004, 06:46 PM   #6
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so you grounded that wire and now it works fine?
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Old 01-19-2004, 09:33 PM   #7
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That is correct.

-Jon
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Old 01-19-2004, 09:59 PM   #8
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what is BWH though?
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Old 01-20-2004, 12:28 AM   #9
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body wireing harness ..yeah a bit too many abrieviations in your post there jon
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Old 01-20-2004, 01:09 AM   #10
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I just figured that people who have replied to my other posts that use the abbreviations would have read the posts and known what they meant. Guess I'll refrain from using any abbreviations unless it is pre-defined within the current post.

No abbreviations now.

-Jon

Last edited by stimpy; 01-20-2004 at 01:14 AM.
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Old 01-20-2004, 12:33 PM   #11
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OK
I had the same probleme and it was the groung for the temp gauge.... just cut the ground wire from your cluster temp gauge and ground it to the body anywhere....

Faf
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Old 01-20-2004, 01:20 PM   #12
stimpy
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Oh, and technically, it is bulkhead wiring harness, not body wiring harness.

-Jon
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Old 01-20-2004, 03:58 PM   #13
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yeah I thought it was bulkhead not body...sorry for not getting your abreviation
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Old 01-20-2004, 05:08 PM   #14
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It's not a problem; I was assuming that those reading would be up to par on my saga, but it really doesn't work for posterity.

-Jon
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Old 02-01-2004, 03:45 PM   #15
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OK I think I have it now...finally got time to look through my schematics...
The RG wire coming off of the temp gauge that is shown running back to the ECU (MFI module) is the wire that needs to be grounded. right?
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Old 02-01-2004, 07:40 PM   #16
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I cannot confirm nor deny that. Read your diagrams and go with it. For the record, though, I did not have the temp gauge wire going to the ECU. It went to the engine.

-Jon
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Old 02-01-2004, 09:53 PM   #17
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well yeah on my 94's wiring diagram one is shown going to power, one coming from the sensor and one going to the ECU (assuming this is the one that needs to be grounded) having read your previous replies.
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Old 02-04-2004, 12:19 AM   #18
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Well, I'm just saying screw it with the dummy gauge, since mine reads full hot. I'm going to put an aftermarket temp gauge in. I think I'd trust that more anyway.

Cam
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Old 02-04-2004, 10:09 AM   #19
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Quote:
Originally posted by Aspen_2.5RS
Well, I'm just saying screw it with the dummy gauge, since mine reads full hot. I'm going to put an aftermarket temp gauge in. I think I'd trust that more anyway.

Cam
I was going to try that but I'll be trying this method first...it's just grounding one wire
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Old 02-05-2004, 12:17 AM   #20
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The older gauge cluster shouldn't be a problem at all. I did a MY00 2.5 conversion into a MY95L (same gauge cluster). No problems arose with the gauges.

The fact that you're not getting any CEL's says you have the thermometer and temp guage wired correctly. You definately need to wire the ground for the Temp gauge and on newer models it goes to the engine ground (GE).

-Adam
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Old 02-05-2004, 12:21 AM   #21
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I have a CEL anyway due to the lack of extra fuel stuff at the tank. I would trust an aftermarket gauge more at this point.

Cam
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