No Tach...My rig let me down

[yARIC008]

Sounds like a blown fuse or bad relay to me. Are there any other symptoms at all? When my main 30 amp fuse went I'd get dim OD light and no tach. Of course I'd get no starter and what not either.

Could it be corrosion on one of the fuse blades? Pull them all out and check? Only other thing I would think is a rubbed through wire somewhere.

 

[FORDF250HDXLT]

the dim od light is your primary focus here Gary.find out why the trans controller isn't getting 12 volts and it will then also restore the tach.

 

[FORDF250HDXLT]

im not much help with the pre '92 trucks because i don't have one.
for those who run into Gary's issue with a 92-94 idi/e40d truck here and find a dim od light (which also results in an inop tach) you can check the eec relay as noted in the above pic (or the "pcm relay" as noted in the attached pic here) and the two fuses here noted in the pic below as "pcm fuses" "I" & "U" and it should restore the dim od light and the tach will then also function again.

roadside tip for the mem bank;
if you find yourself with this issue while on the road but both fuses are ok.you can swap in the horn relay to get ya home like normal,rather than limp.

i don't know where fuses are in your truck that powers your trans relay Gary,sorry.
however if you find the problem and restore the power,the od light wont glow dim anymore and the tach will then begin to work as normal.best of luck.

 

[icanfixall]

I fixed it...turns out the tach died. I installed the replacement tach I got with a complete cluster for 35 bucks. Now I have a nearly complete spare cluster. Thanks everyone for the help and support. Its never easy for me when I have electrical issues.

 

[trackspeeder]

Cool. $35 bucks and some spare parts for behind the seat.

 

[icanfixall]

Cool. $35 bucks and some spare parts for behind the seat.

You betcha... Nothing like behind the seat spare parts. Might be time to organize and build shelves back there...

 

[jrad235]

That's the downside of spare parts, you have to find somewhere to keep them. Hence why my garage and shed are full of vehicle parts. Best to stick with one model of vehicle.

 

[icanfixall]

Well crap.. I tested the rig yesterday and it drove fine. But today I needed it for a dr appt and its not shifting once again. Appears the same issue. Dim od light on dash and no tach.... So I drove it anyway.. **** on it... Drove fine I guess. My starts were in second gear and I could only shift to third manually. No overdrive. All I did differently from yesterdays short drive was hose off the hood and dirty windshield. Used the wipers to scrape off the dust after the watering. Also noticed the dash temp gauge was fluctuating so maybe its a dash ground. Anyone know where the dash ground is located??? Another ****** day under the dash.. Might just go to another wrecking yard and purchase another tach because that seems to have fixed my original problem although I can't really test my old tach...

 

[icanfixall]

the dim od light is your primary focus here Gary.find out why the trans controller isn't getting 12 volts and it will then also restore the tach.

Well I checked the voltage on these terminals. My teca the 88 to 91 style. So on terminal "A" I should have 12 volts ignition on and I do. It has zero volts ignition off. The "C" terminal has 2.8 volts all the time when its supposed to have 12 volts all the time. This location has 2 yellow wires in the same location very similar to the supply lines for our solid state glow plug controller has. So I made up a jumper wire from just under the plug connection to the relay and directly to the drivers side battery hot side. Instant usable tach once again. So where does the power come from to those 2 yellow wires in the teca relay plug. I don't drink alcohol but I just may end up drinking to forget this trouble. I simply hate wiring issues.

 

[The Bus]

I found this post with wiring diagrams for a 1989:

http://www.oilburners.net/forums/showthread.php?44434-Wiring-Diagrams-%281989%29

It looks as if from the first diagram, that one of the Yellow Wires going to the TECA Power Relay connects to a "20 Ga. blue fuse link".

I would re-check all the grounds and connections. I was having some trailer light issues the other day . A couple of connections were not good along with a ground needing some cleaning - lo to no voltage reading from the relay. All appeared good shape until I put the tester leads on them. I took them apart, cleaned them, put them back together and bingo they work properly. Once you eliminate the wire itself, you can move on to the components.

I hate to ask, but did you check any of the known connections point to point for continuity?

As odd as it may seem, you might have a broken wire. If the copper was contaminated when it was drawn, it will corrode and break apart inside the cover over time. It looks like a knot under the insulation. I learned this when working on my first car, an old Mustang. It takes about 15 - 20 years for the decay to occur to the point of failure. Never knew until I spoke to restoration expert. Spent some coin on switches and relays that i did not need to.

I had to run continuity test on my wiring harness. It was one of the most aggravating things to be so simple to fix.

 

[The Bus]

Found another thread on another site addressing the same problem.

cdnsarguy (good source of info by the way) post #4

Re: Tach not always working ..?
Check all the connections, there are a few including the main engine harness connector on the drvrs fender. Are the wires at the top of the sensor bare if so they will short out.

Go down to Post #6 for some positive results:

Re: Tach not always working ..?

I have a new tach sensor with taxes it was $99.80CDN but I didn't put it in yet ... The sensor in it is less than a year old ,and tests 2530 ohms (good is 2000-3000 ohms) .. I checked the firewall wires cleaned some with contact cleaner and put dielectric grease on them .. Also cleaned the wires on the back of the dash assy ,Ford made a cheap circuit board when they made that it's just flexable plastic.. Anyway it's working now but it worked sometimes anyway so I guess I'll have to watch it and see if it stops working again ..

http://www.thedieselstop.com/forums/f30/tach-not-always-working-113806/

 

[icanfixall]

Well as I posted I found the relay 12 volts all the time is only getting 2.8 volts. Its the 2 yellow wires. So doing a little more reading I found this power feed comes from the passenger side fender solenoid. Now its a fused wire so I'm guessing that means it goes to the under dash fuse panel but it might be on a fuse able link. Not sure yet. I will be digging into this because the way its hotted up now is a simple jumper from the drivers side battery hot terminal directly to the relay double yellow wire.

 

[laserjock]

Worst comes to worse Gary you could always wire it that way with the appropriate size inline fuse I suppose to protect the TECA.

 

[79jasper]

I believe those are fusible link wires.

Sent from my SAMSUNG-SM-G890A using Tapatalk

 

[icanfixall]

I was talking to Al aka Roitwarrior up in Canada today about this might be a fusible link and how to test for it. Got to put some pants on and go out and start testing for continuity.... Just lazy as hell today after cooking all day.. Wifey wants some chicken ******* slow cooked in our .. Well her new crock pot. Went out and collected onions and herbs from the garden. Just hope I got the correct ones. If not I will be visiting Carl's Jr for dinner.... Still have to make spaghetti and then some roasted carrots.... I'm a simple eater... Meat and potaos is what gets me by... Maybe some bacon to add some flavor... One can never have too much bacon...