Early Twin Cam Tach Issues - Harley Forum

highlander426 · #1 09-01-2009, 03:58 PM

I'm having tach issues and am hoping someone else has had a similar issue, so I can figure out my next step.

1999 Electra Glide twin cam 20k miles. Had big bore kit, cams, power commander, oil pump lifters, cam support plate, etc updated in early 2007 at 15k. Bike runs great!
Issue started late 2007 at 18k, tach started to jump around, or not display rpm. Shut it off, restart, works fine. Then tach started to work less and less often. Sometimes would go for weeks without working, but bike runs great!
2009 - After driving bike for a few weeks, and tach not working, all the sudden tach works for about 1 day! Tach works intermittenly, and jumps around alot. Right now tach not working again, but bike runs great!
So, Here's what I've done since late last year:
1. Found used tach that worked. Put it in, nothing. Put in old tach and left it at that. After riding a few weeks pretty steady, tach starts working, but very little and intermittenly. After not riding for a little while, nothing.
2. Checked continuity of pink tach wire from as close to ECM as I can get all the way to the tach plug behind fairing and wire appears to be fine, no shorts. Can only trace it so far without removing tank and all wire looms.
3. Used dialectric grease on all plugs and wire connections inside wire harness to try to rule out moisture or corrosion.

Long winded info, Question:

Where does the tach/ecm get the rpm feed from? Crank sensor, cam sensor?

I would like to try to figure this out without having to take it to the dealer and have them go thru the same stuff and charge me an arm and leg! It could be the ECM, but I would like to rule out the crank/cam sensors if I can before I have to consider replacing the ECM.

Any thoughts would be appreciated.

Thanks in advance.

aceharleywrench · #2 09-01-2009, 05:37 PM

Try cleaning out the deutsch connectors that connect the crank & cam position sensors to the main harness,these have a tendency to get contaminated.

highlander426 · #3 09-02-2009, 07:19 AM

Thanks for the input

. I'll take a look and post a note on what I find.

Thanks again.

highlander426 · #4 09-02-2009, 09:24 PM

Well, Here's the scoop. I checked the plug located under the cam cover/frame area for the cam/crank/oil pressure guage duetsch connector. (That's right! All three items are in one 8 pin connector, only 7 are used), and it looked clean as a whistle! No corrosion or anything. The pins appear to be straight. None look bent or damaged. I put dielectric grease in it as well and put it back together, but to no availe. Still no tach. I'll probably take it back apart again this weekend and make sure none of the pins are out of alignment.

That is the only plug I can see between the parts and where the wires go up under the seat area.

Thanks for the post.

highlander426 · #5 11-12-2009, 02:57 PM

I have taken the bike to Capital HD in Diamondale, MI and they say that it is the ECM. The part number is 32423-99C. I'm sure a rev A or B would work also. They say it is back ordered and have no idea when it may come in, and no other dealers around seem to have one. If anyone knows where I can get one, please let me know. You can reply to me at:
duncanmacleod@ameritech.net or clannadmacleod@yahoo.com

Thanks again.