[Don Rodgers]

Recently I replaced the coolant temp sensor that attaches to the right intake manifold (36151-MT8-003) because my 1991 Aspencade (with a 1990 motor) surges at some rpm levels with the choke on or if the idle is set higher than about 800. I read several threads that indicate this is a possible cure for surging. In doing so I discovered that what my Clymer manual calls the coolant temp sensor is not this part but the sensor that is located in the thermostat housing (37750-PC1-004) . I was a little disappointed and surprised at my ignorance because I didn't actually realize I was preparing to remove the wrong part until I disconnected the wire and realized that it was not gonna fit the new part I bought.
All this to say that I also realized that my Coolant Temp Guage on my dash doesn't work. (More disappointment and surprise at my ignorance.) In my defense, the motor never runs hot and has never overheated and the needle on the guage actually moves up a little bit whenever the key is on. And the fans work.
I assume the part #37750-PC1-004 (called the sending unit on the Cyclemax parts diagram) is not working. The needle on the temp guage never moves past the original twitch, even when I let it idle until the fans come on. If I remove this part I'm gonna replace it.
My question is this. Is a bad sending unit the only possible reason my temp guage doesn't work?

 

[DaveO430]

My question is this. Is a bad sending unit the only possible reason my temp guage doesn't work?

No it is not. A bad connection somewhere in the harness would also cause that. There are 3 connections between the sender and the gauge.

 

[DriverRider]

On the left side of thermostat housing remove the green/blue gauge sender wire and momentarily short that wire to a good ground with jumper wire and key on. If wiring and gauge are responding it should send gauge needle full right (hot). With wire not grounded gauge should be to the left (cold).

 

[DBohrer]

Don, There are four connectors involved.

1. C-22 Red "6-pin" Behind the right fairing panel on top of the fan shroud.

2. C-55 White "13-pin" Behind the right fairing pocket.

3. C-66 White "20-pin" Behind the instrument panel.

4. C-108 White "6-pin" Behind the instrument panel.

The Green/Blue sending unit wire passes through each of these four connectors.

Have you worked in or around the C-22 or C-55 connector areas.....??

BTW...Does your fuel gauge work....???

 

[Don Rodgers]

Yes, the fuel gauge works.
Also, I installed new coolant when I drained the system to replace the sensor and have checked the level in the expansion tank and topped it off with a cup or so after running it until the fans came on (after it cooled down again).
I do not understand the numbered connector references. I understand what you are talking about and I can picture the locations, but I don't see the connectors identified on the diagrams in the Clymer manual that I use.
Also, I apologize for my account profile being goofed up. I'll try to fix it.

 

[DaveO430]

I do not understand the numbered connector references. I understand what you are talking about and I can picture the locations, but I don't see the connectors identified on the diagrams in the Clymer manual that I use.

In the Honda electrical manuals the connectors are numbered and identified by pin # and color, the location given and a picture of the locations. Wiring diagrams of each system are separate and laid out in a very easy to follow top to bottom + to - manner.

 

[DBohrer]

Don, The Honda manual is much better than the Clymer manual (especially for electrical work).

Hope you are doing well....!

 

[AZgl1800]

Yes, the fuel gauge works.

Also, I apologize for my account profile being goofed up. I'll try to fix it.

this new software is a bit buggy with the Profile.... nothing shows up unless it is entered into the Signature, and I saw your statement about the bike, and edited your Signature line for you.
Job 1 done.