No Tach...My rig let me down

[icanfixall]

My rig has sat untouched for about 11 days. Never a flicker the tach was going to stop working. checked the plug and wires near it and moved them. Still nothing. Test drove about 300 yards and no shift unless I do it manually. Have not looked at the tps but feel that is not an issue. May try checking the engine main wire harness plug later. I hate electrical problems.

 

[icanfixall]

Well we have plenty of lookers here but no suggestions. Heres what I have checked. Checked the plug from the sender. Thats the 2 black wire plug. No change. So I replaced the tach sender. Still no tach. So opened the engine main wire harness plug. Greased it and returned to service. Still no change or tach. Pluueled evry fuse and found no issues and still same problem. No tach. So I have a dim od light showing. No tach reading and no problems with fuses. Whats next. Of course the only reason I tried using the truck is I need it. But hell.. I'm let down. So now having a cool one and watching for suggestions.

 

[cpdenton]

Dim OD light usually means a TCM relay problem, right? The TCM isn't getting power properly, which also causes the tach signal to not get to the tach.

 

[KZF250]

I certainly wish I could help Gary as a small token of appreciation for all the useful posts I've read of yours...so I will just follow the thread and hope you get her dialed in sooner rather than later.

 

[icanfixall]

Well at least I have something to look at. So I will try testing some relays I know of on the drivers side fender well. Have no idea which replays or how to test them besides replacing them. Will look for corrosion or issues.

 

[cpdenton]

Wish I knew which relay it was Gary. Mine having a zf swap, I have never had any issues with it. I still have the TECA, and if my relay quit, the tach would too, but it hasn't yet.

 

[BDCarrillo]

Put a VOM on the sensor with engine idling. You're looking for AC voltage from one sensor wire to another.

Resistance should read about 25k ohms.

Other diagnostics of the sensor require an IP gear chucked in a drill press...

If the sensor passes, check continuity of the sensor ground and signal wires. I don't know how to test the tach gauge itself, but have a functional spare I can send you.

Also, verify that the tach is getting 12v, ground, and signal through the three little pins that fit into the gauge cluster, which then goes through the printed PCB and into one of the plugs. Lots of points of failure in that whole assembly!

Btw, I can't remember if the TECA is upstream or downstream of the tach... I kinda lean towards a faulty sensor/wiring since neither the tach nor TECA appear to register RPMs

 

[icanfixall]

Well under the black piece of plastic cover just behind the coolant recovery bottle I found one relay. Its ford number is E3AF 12646-A. This is the only relay I can find. It appears to fit several different ford products. Not just a diesel only relay. Anyone know what this relay is before I buy another one? Throwing new parts at my rig hoping to fix it really can be embarrassing.

 

[icanfixall]

relay replaced but still same problem. No tach and dim od light. Now what do I do next.

 

[kcwright1979]

Could it be that the instrument cluster or the tach itself. Seems like you have eliminated everything else.
Just my .02

 

[3Kp]

Gary I'm having the same issue. I was reading that a OBD1 code reader will help get the codes off the transmission. But I went and looked at one at the AP store and says it excludes diesels? Probably due to it's ussed to test the EEC system? From what I read you connect it to the transmission control harness and count the flashes of the light on the OD button to get the codes.

There is a relay on drivers fender it a TECA relay its between 2 test connectors next to washer fluid motor.

 

[BDCarrillo]

OBD1 readers will read our E4ODs just fine...

 

[OLDBULL8]

This is for an 89.

 

[icanfixall]

Gary I'm having the same issue. I was reading that a OBD1 code reader will help get the codes off the transmission. But I went and looked at one at the AP store and says it excludes diesels? Probably due to it's ussed to test the EEC system? From what I read you connect it to the transmission control harness and count the flashes of the light on the OD button to get the codes.

There is a relay on drivers fender it a TECA relay its between 2 test connectors next to washer fluid motor.

I replaced this relay found under the black plastic cover. Still same problem. I tested the plug and have power on the hot always post number 4 of about 1.88 volts key off. then with key on engine off I still have that voltage on that post ans power on post number 1&2 as expected. I replaced the fuse on the number 18 port with a new 15 amp fuse. Still same. Getting a stupid feeling about this. I'm just not very good with electrical issues. And did I say its hot here today and I really need this truck to run.

 

[icanfixall]

Thanks Bill. Will dig in to the instrument cluster and check voltage and resistance. So far what I am reading in the plug to the teca relay is low voltage on the posts that should have 12 volts when the key is off. then when I turn key on but engine off the other 2 posts that now should have 12 volts do not . they have a low volt reading. I also tested the tps and found it has a very low voltage reading at .07. Nothing was worked on for that to change. so where do I go for a ground issue on this circut? Where is the actual ground fastened to the truck for the teca?