JD730

It seems to only do this when its cold. Turn the key on and the 'wait to start' light is flashing rapidly and you can hear a relay clicking under the hood. I've managed to locate the offending relay. Its the one closest to the battery on the fender.

I have a few questions.
Has anyone else had similar behavior?
If so, is the relay on its way out or is the PCM thats controlling the relay giving up?


Thanks in advance.

wannadiesel

Which unit is this? According to my Cummins book, a flashing WTS light means an open air temp sensor circuit, but I don't think the Dodge PCM in the intercooled trucks behaves the same way.

JD730

Thanks Dave. This is one of the 93's, the non-intercooled truck I have is for parts. It will eventually latch and heat the grid and it doesn't do this when the temps are between 60F and 40F.

It will start, but it would be nice to do it without putting up a smoke screen.

wannadiesel

Huh, that's an odd one. Have you checked the battery voltage while it's engaged in this behavior?

JD730

Hmmm, looks like something to do when I get home from work tomorrow.

rustbucket

having the same problem,so far haven't found the answer. wondering if it could be something wrong with the ecm.

silverbullet02

Yeah, keep us updated. Mine will come on and flash in the cold weather, and now that it's in the 20's-30's, it just flashes and doesn't go off. One day the grids just didn't turn off and almost melted the wire, so they've been unplugged for well over a year now. And I pulled the light bulb out of the WTS light today so I don't have to see the darn thing all the time. Be neat if I could fix this, but not high on the priority list at the moment.

JD730

I was just getting ready to go out a fool with it, when I saw some bring it back up to top. I haven't had time to work on it. Truck will still start, so it wasn't first priorty. If I fix you guys will be the first to know.

JD730

Well, I just got back from working on it. The relay I mention in my first post, has nothing to do with the intake heater relays.

This is what happened when I turned the key, it had been below 10* overnight here.
Nothing, no relays clicked at all.
Battery voltage a that moment was 11.8 (could be alittle low, but it started the truck fine this morning) with the fan for the heater running.
Pulled off one the wires off each intake heater relay, battery voltage at each of them.
Pulled the plug out of them relay mention earilier and checked for battery voltage. Plugged it back in and a moment later it started clicking. Fast at first, then it slowed down and eventually latched. Plugged one of the intake relays in and click. hmm.
Cycled the key off then one again. CLICK, everything working the way it should.

Rustbucket, I'm thinking the same thing, right now I think the ECM electronics can't handle the extreme cold for some reason. The components that energize the relays can't sink enough current to do it and the clatter like they do or the component that is controlling them is doing it. Another thing I noticed a while back when it was doing this is that my digital tach would go nuts and that gets signal from the ECM. After the relay's stopped clicking it worked normal.

It looks like I'm going to put manual controlls onto the intake heating system for now.

wannadiesel

Mike, this is really wierd. The relay that's clicking is the ASD relay, it sends power to the field circuit in the alternator. That relay should not be energized until the crank position sensor is reading over 400 RPM. For some reason the PCM thinks the engine is running when the key is first turned. My only suggestions are to check out the crank sensor and its wiring.

JD730

That could explain why I see funny numbers on my tach when its trying to engergize that relay. Whats troubling me is the fact is doesn't energize it completely, its clicking on/off rapidly till it completely energizes.

wannadiesel

That'll do it. You are getting some funky input from the crank sensor - could be the sensor, could be the wiring.

rustbucket

just instaled new ecu on truck,everthing works now,pre heater comes on instantly now.

2500WHITERAM

ditto...ive seen this a time or two before