91 CBR Temp Gauge Help
 

Hey all,

I'm new to the website and to the motorcycle scene. I've just purchased my first bike, a 91 F2. My temperature gauge doesn't work what so ever. Just curious to know if anyone has any ideas?

Thanks.

Yeah - probably a sending unit issue. From your other thread it sounds like your bike has a few small electrical gremlins, but nothing that can't be sorted out.

this is a gauge, wiring or Sensor issue

For simplicity sake - test the gauge first - the gauge has 3 wires feeding it - find the 7 wire connector that feeds the gauge cluster. (you don't have to unplug the connector) You're looking for green wire with blue stripe. That's the signal wire from the ECT sensor. Ground that wire with the key on (backprobe the connector), or if it is easier to do this at the gauge itself, that's fine too. with the Green/blue wire grounded, the gauge should move to Hot. Only do this for a second or 2 max just to see if the needle moves. If it doesn't, Test voltage - the Black/Brown wire is your 12V positive, dark green is negative. You should be getting 12V there.

To test the ECT (engine coolant temp) sensor - on the F2 I think it is under the tank, between the framerail and the airbox - screwed down into the head - it's hard to tell from the Honda manual I have on my PC (I've never had to check mine before - sorry).

Unplug the wire from the sensor, and ground it to the frame. with the Key in "ON" the tem gauge should move all the way to Hot. don't leave the wire grounded longer than it takes you to diagnose if the sensor is an issue.

you know - looking at the wiring schematic, that Black/Brown wire that feeds 12V+ to the coolant gauge is also the positive feed for the sidestand bulb, oil pressure bulb, and neutral bulb in the gauge cluster. Only those bulbs, which you've been having issues with from your other thread. I'm betting there's some common issue here. You decent with a wiring schematic and a voltage tester?

that Black/Brown wire is fed from fuse C (15A) in the fusepanel, and it also sends juice to the Front and rear brake light switches, and the turn signal relay.

What other thread? Lol. I think this is the first thread I started other then introducing myself. :) But my side stand bulb always stays on. Never goes off. I actually just pulled the bulb so I don't have to stare at the annoying yellow light. And the neutral light seems to work fine. I don't remember off the top of my head. Ha. I'll have to look tonight when I get home.

Ahh - then I confused 2 new F2 owner's intro threads.

Sorry bout that.

but, to help you out, yeah pull the cluster out and ground at the gauge first - see if it operates. Then lets go from there.

Sidestand bulb being lit is one thing, but weird cause I thought signal to light that bulb, should kill the motor as well. Lemme revisit the wiring schematic.

Looking at the schematic - I'd guess your side stand switch is broken internally and the contacts are stuck in the "down position" which is putting ground to the Yellow/Black wire coming out of it. That wire is what carries ground to the bulb in the gauge cluster.
For the bike to run while in gear, the ignition system has to see ground on the Green/white wire coming out of the sidestand switch. I'm guessing that wire might have been purposely grounded?

This would mean the bike might possibly start while in gear, with the stand down, without the clutch being pulled in. Which is potentially unsafe cause it would roll the bike off the sidestand.

there are other reasons this might be happening - the switch couldbe perfectly Ok, and the yellow/black wire to the cluster is grounding out somewhere along the way - would cause the same thing.

It starts with the clutch in, and side stand down so that is a good possibility. I didn't have time to look into it yesterday. Maybe tonight. I seriously appreciate the help though.

You can get a copy of the Honda service manual here: www.stephygee.com/F2manual.zip

that one is missing the 1st chapter that answers some common questions like capacities and stuff - if you download the F3 manual, a lot of the F3's info is still valid for the F2, or pretty close: www.stephygee.com/F3manual.zip

I like keeping the PDF files on my PC and phone (in my Dropbox account really, so I can get to it from anywhere) - and for shiggles, I keep most of the whole honda lineup stored there to help others. It's nice to have access to wiring schematics for questions like these.

the Clymer manual is a much better detailed shop manual, but they're pricey - if you find one for $15shipped or less, it's a bargain.

:icon_ditto:

+ 1 on the Clymer manual... I have all 3 manuals: the Honda, Haynes, and Clymer, and I probably use the Clymer the most.