I just got a 97 Ram 3500 today. My tach does not work. All other gauges work like they should. Also the A/C //Heat does not blow out the vents. It blows out on the floor and defroster though. Any suggestions would be much appreciated.

Thanks,
Brian in NC

 

OK I went for a drive today and now my check engine light, gen light, wait to start kept flashing every once in a while. My tach started bobbing up and down too.

Does this sound like the crank sensor??
Thanks,
Brian in NC

 

It could be the engine speed sensor located at the bottom engine pulley or the wiring to it.
Usually when this is bad though you lose all electronic functions as the computer will think the engine isn't running.

 

OK thats the sensor I was thinking of but was calling it a crankshaft sensor but its a ENGINE SPEED SENSOR. I am going to replace it tomorrow. Hopefully that will cure it if not I'll look at the wires going to the sensor.

Now this is weird. I went to a friends garage to replace my rear brake shoes and on the way there the gauges were acting up and the headlights kept going dim when the wait to start light came on. But on the way home after I put the new brake shoes on the tach and gauges worked and did not act up one time on the way home. Just a coincidence I guess.
Thanks,
Brian

 

You are supposed to set the gap between the sensor and dampener (pulley) with a non-magnetic feeler gauge.
An old credit card works for me, some people use a matchbook cover.

Don't know why the moderator moved this to the 24 valve section.

 

Not sure either. Its a 97 3500 12 valve.
I read to use a brass feeler gauge and not metal in the manual. Thanks for the heads up though. I hope this is the problem. I've been reading some other members electrical horror stories.
Thanks,
Brian in NC

 

Probably that newbie moderator, still training.


phox

 

For the vents/heater problem you need to look at the vacuum lines for a disconnected or leaking line. Defrost is the default position when you have no vacuum to the system.

Kim

 

Yeah I was fooling around with the selector today and on the first selection which is fresh air I heard a slight hissing sound just behind the selector panel. I haven't pulled the panel off yet to check the vacuum hoses there but I'm sure one is cracked or unhooked.

I did order the supposed to be Engine Speed Sensor (ESS) but the Advance and Autozone puter call it a Crank Position Sensor. A hair over $100. The ESS, which they had in stock and was the wrong part I think goes in a automatic transmission. It had threads and had a O-ring on it. Looked like a hall type sensor too.
Thanks,
Brian in NC

 

Hope the Crank Position Sensor is the right part.
A CPS is only used on 24 valves and gassers.

 

Thanks for the information about the vacuum and the default on the vents. Mine just started to run on defrost only, and I was unsure where to start looking. Thanks.

 

Me too. It looked like the right part from the picture the lady showed me on the parts computer but you know how that goes sometimes. The ESS I got was only 21.99 and this watch they call Crank Sensor is 108.99 so I hope its the right one. I'll find out in the morning.
Thanks,
Brian

 

Advance and Autozone call the ESS which is on the front of the motor hovering over the harmonic balancer a crank position sensor. I got it this morning and put it on and all is well.............so far

Thanks for the info and moral support.
Brian in NC

 

My dealer called the one on the front, the crank speed sensor as well.

 

That would be more correct than crank position sensor.
The position sensor is used to vary timing on an electronically controlled engine.
Us poor 12 valvers have to pull off a gear and move it