MCI DL3 Looking for spare wires/bundle location re: Temp Gauge differences

[plyonsMC9]

Good evening bus folk!

My front gauge reads about 25-30 degrees hotter than the newly installed mechanical gauge.  I've been troubleshooting this one a while.  Heat gun also verifies that mechanical is accurate.  I ran a test lead from the sending unit (I've tried 2 different sending units what are matched to the new temp gauge) to the dash gauge.  With the  lead (65 foot 14 gau stranded) in place and the original cable disconnected from the dash gauge, I now have "only" a difference of about 10 degrees.  Not perfect but a lot better. 

So my question is, where are the spare wires?  I seem to remember reading a few posts where the solution was to pickup an unused wire and try that, vs. running an entirely new wire front to rear.  Going over the manual and not finding it easily spelled out.  I have a bundle in the driver's junction box, starting w/ labels "sp..."  are those spares?  They aren't terminated (Picture).  Any suggestions on where they end up or how to find the other ends?  I thought I could just find something for the galley or restroom but not seeing anything like that in the front j-box.

Thank you!!! Kind Regards,
Phil

[chessie4905]

Go to harbor freight and buy a cable tracker ( wire tracer ). Works real nice to trace wires. You clip a sender to the wire and use a small box with antenna at rear area. Itll give an audible signal when you locate the other end. Not that expensive either.

[richard5933]

Do you have a matching bundle of non-terminated wires in the forward electric panel? If so, match 'em up color for color and stripe for stripe.

Not sure about the MCIs, but GM seems to have included both terminated and non-terminated spares in their harness. If your wiring diagram is any good and shows a breakdown of the wires in the rear & forward electric panels you should be able to find which are which.

Otherwise, are there any similarly numbered terminals in both forward & rear panels with only one wire attached?

[plyonsMC9]

Thanks very much folks!

Wow - cable tracker looks fascinating - and sounds like it could be very helpful in this situation.  Thank you!!

Re: spare cables - what I have in the picture I attached is a bundle of unterminated wires in the front junction box.  But I don't see anything that looks like those unterminated wires in the rear junction box (or the manuals so far).  Possibly cable tracker could help.  I'll keep looking though, for someplace else to look for those matching black cables. 

With best regards, Phil

[freds]

Otherwise, are there any similarly numbered terminals in both forward & rear panels with only one wire attached?

One wire attached is a good indicator. However on the Prevost buses they don't bloody use matching terminals.

I have had not much luck with signal tracers as there seems to be quite a bit of signal trace over.

I find it's best to inject an odd voltage (for a bus) like 5V to indicate the right terminal.

[plyonsMC9]

Thanks Fred - I like that idea re: odd voltage. 

Much appreciated, Phil

[plyonsMC9]

Good afternoon Bus folks!

Still working on this MCI in dash gauge issue where the dash gauge is a good 20+ than the mechanical, and laser temp gun.  We have swapped dash gauges, sending units, and run a stranded 14 gau wire bypassing the internal wires from temp sending unit directly to the gauge.  Only the wire bypass seemed to make a significant impact in lowering the temperature displayed on the in dash gauge to a point where it's closer to the rear mechanical gauge. 

I have two questions;
Does the same wire from the sending unit T off and one lead goes to the ECM, and the other to the dash gauge (This is an old DDEC II).

How should this setup work ?  As heat increases, resistance decreases, and magic happens?  My Internet searches aren't yielding the clarity I was looking for.

Thank you folks!!!
Kind Regards, Phil

[Iceni John]

If the gauge is reading a few degrees too hot, try putting a low-ohms variable resistor in the circuit, then you can fine-tune the gauge to read exactly correct.   I did this with my old transmission temperature gauge that was hopelessly inaccurate, but I subsequently replaced it with a Speedhut gauge that's accurate out of the box.   Also, the ground must be without resistance, so it's worth cleaning or replacing its terminals.

John

[Dave5Cs]

When usin a Toner, Signal tracer, cable tracker, etc. Make sure you disconnect any power on the Bus to include all batteries, shore, solar  or any other power that would interfere with a trace. Then connect to one wire at a time at one end and check at points you think might be the end or a middle connection. Pull connecting end away from other wires or terminals by about 2 inches if possible then you won't get over feed.
Also on MCI's if you are looking at finding original wires they should have a small marked numbered metal tab on the ends of the wires so that you can find at each connection.