reman ECM seemed to do it , but now.........current drain thru ecm?

[fatbloke-dim]

If anyone has followed my other posts on the ECM saga for my '93 , you may be aware that the re-man ECM seemed to hit the spot . But ! - The car died on me due to a duff battery , it went flat and the car cut out whilst driving at about 70mph . The battery load-tested "kaput" , so a new one is now fitted . Trouble is , there appears to be a current drain , around 270 milliAmps to the ECM with the ignition off . Don't know where the current is going , but I think it may be FROM the CCM , but not certain on that point . Is this normal ? I think it be a bit high . Or , could the fact that the battery was defective be an issue , ie,not enough capacity to sustain engine running and lights on , and if so , is it poss the new battery would allow the car to operate normally without dying on me . It is not very relaxing if you're expecting the car to choke on you at any moment !

Any ideas about that current draw ?
Thanx in anticipation , folks .
S'all for now .
FB-D.

 

[Hib Halverson]

C4 will never draw zero current unless you disconnect the battery.

270mA is likely no problem. The ECM constantly uses current to store volatile parameters in memory.

Get a smart trickle charger. Auto Meter Battery Extender is what I use.

 

[boomdriver]

This is all assuming that the alternator is charging within normal range...somewhere between 12.5 and 14.5 ?

 

[Hib Halverson]

This is all assuming that the alternator is charging within normal range...somewhere between 12.5 and 14.5 ?

I'm pretty sure the OP was talking about parasitic draw with the engine off, not charge voltage when the engine is running.

 

[fatbloke-dim]

Yes , I was referring to parasitic draw , that's the 270-ish mA current measured . At the same time , the sparky checked the alternator output , which registered just over 14V , occasionally just a skosh shy of "closer to 15 than 14" , if you see what I mean . Certainly charging , but a little high but not enough to be of any great concern , he felt . It seems like the new battery may have done the trick , as I've run out for another 100 miles or so , around 35 with the lights on and the dash voltmeter indicates steady at around 13V , even with the lights on . The car has now been sitting for a couple of days ,so I'll see how the battery has held up . I realise the dash voltmeter is only a relative "ballpark" indication and not an accurate meter , but it goes a long way in giving me a bit more confidence in the car . That ECM does get bloody hot , tho' under the hood ! I leave the hood up to let things cool ,if I can do so safely ,each time I am parked for a while . I will be getting one of those battery disconnect widgets , tho ' , and I do have a battery tender , but will have to bring the batery indoors to use it , so the disconnector will do the job whilst the car is in use , but not going anywhere for a day or two , just to be sure . Just now , our usually lousy Brit weather is going completely and utterly crackers - it's hotter now , in October than at any time in the "summer" . It's going to be 82 degrees and cloudless ! Time to get the ' Vette ! Must make hay while the sun shines , and I will tempt fate and suggest that the car seems to be fixed ! Prob'ly should'nt have said that :L .
Anyhoo.... I'll see how things go , have planned another trip of around 100 miles this afternoon , to a beautiful country pub , that is an absolute gem . The landlord is an avid collector of antiques and all manner of curiosities and ephemera , and my particular fave , breweriana . Even one of Queen Victoria's stockings is in the collection . A run in the ' Vette will make the one pint I dare have whilst driving taste like nectar !

Thanks to Hib , Boomdriver , and everyone who has chipped in with sage advice , your help has served to enrich my Corvette ownership . Really . If there's anything to report , I'll post up , hopefully it might just be "nothing to report " .

Cheers, fella's
keep the faith ,
Nigel H.

 

[John Robinson]

The voltage you see on the cars instruments is probably wrong if your 93 is like mine. I also showed 15 volts at times when charging so I did the following.



I purchased a gigar lighter plug with an on off switch and in line fuse. I then used my voltmeter to monitor the battery voltage and compare it to the instruments. My readings showed both of the car voltage meters to be different from each other and compared to the voltmeter they ran as much as 1 to 2 volts higher.


You could do the same thing by running wires directly from the battery to the volt meter and then drive the car. For safety's sake have someone with you to monitor the meters

 

[Hib Halverson]

The analog gauges in the late C4 IP are notoriously inaccurate.

Not sure a 93 has the same features as my 95 but if your dash has a "gauges" button, press it and look at the IP under the speedometer. If there is a digital voltage display, use that.

Remember voltage is pressure and amperage is flow. At operating temperature, the late C4 alternator will usually generate 13.5-15 volts, even if the charge rate is low.

Do not put a battery cutoff switch on the car. If you do, the ECM will have to "relearn" every time you start the engine. 81-93 need battery power to preserve that memory. Use a high-quality, "smart" batter charger, such as the Auto Meter Battery Extender. When you're not driving the car for periods longer than 10 days or so, keep it connected.

 

[John Robinson]

The analog gauges in the late C4 IP are notoriously inaccurate.

Not sure a 93 has the same features as my 95 but if your dash has a "gauges" button, press it and look at the IP under the speedometer. If there is a digital voltage display, use that.

Remember voltage is pressure and amperage is flow. At operating temperature, the late C4 alternator will usually generate 13.5-15 volts, even if the charge rate is low.

Do not put a battery cutoff switch on the car. If you do, the ECM will have to "relearn" every time you start the engine. 81-93 need battery power to preserve that memory. Use a high-quality, "smart" batter charger, such as the Auto Meter Battery Extender. When you're not driving the car for periods longer than 10 days or so, keep it connected.

Hib
As I mentioned in my post both of the meters the analog and the digital were off. If I remember right the analog was about 1 volt to high and the digital was about 3/4 of a volt lower than my meter at the same time.

For information to the OP my voltage goes to about 15 volts after starting until the engine has run a couple of miles then it settles in at about 13.2 for continouis running with or without lights.
When in traffic and the fans kick in then the voltage is in the 14 volt range until they go off. I can only speak for my car but that is how it has been for the 6 years I have owned it.

 

[fatbloke-dim]

The reference to the dash voltmeters are given as purely relative indication ie , is the batt up , down , dying , keping up or whatever whilst driving , the figures stated for the alternator output are actual multimeter readings . The sparky who attended said that the charge rate was OK , but I can't for the life of me remeber what he said it was Amp-wise . Must be me age , and C.R.S. syndrome ! I recall he said it was well within the alternators measured capacity to cope with the current drawn with lights , fans , AC etc thrashing away , so no charging issues . Todays run out was trouble free apart from every Magoo-eyed jerk was out for a run , too . Cripes !
As for the battery tender/optimiser/charger , that would only be available when the car is at home , when it finally gets a garage , it will be remote from home and no power supply available , so it looks like the battery may be brought home if the car is'nt going to get used for a while . If it has to re-learn the fuelling etc., then so be it I guess , unless this is likely to cause any further issues . Does this harm anything ?

 

[John Robinson]

I don't know about you but I sure would not want to have to take the battery home to charge since you have to remove the fender panel to do it. I have had mine sit for a couple of weeks and it started rightup. The way I see it is this the battery in my watch goes continouisly for years with out failing. The battery in my pacemaker has been in there for 6years now and it still test OK. The point being that if everything is as it should be then stop worrying about it. I have stored cars and motorcycles for the winter months and they started right up without charging the battery.

 

[fatbloke-dim]

Hey ,John....

I'll bet your pacemaker does'nt have Corvette electronix in it ! Thing with watches is they operate on microscopic currents , 'Vettes have more "manly" demands ! All seems to be well , the car has now sat for nearly a week due to "pissistent " rain - this is England , after all , and Manchester in particular . Friday looks good for a trip out ,so the acid test will be if it starts then . When out the dash IP readout says all charge funtions and voltages are ok , the car has done nothing to make me think otherwise . So it seems like it be a case of "only needs driving " . The issue with battery disconnexion is that if I get a garage , it will be a lock-up , and some distance from home ,and will have no electricity suppy . The car has had to go thru' the re-learn process a couple of times now , and it does'nt seem to cause any bother . Probably should'nt have said that , either ! For a good few years the car had lived in a heated ,deluxe garage until I got it . That'll be a shock to it's sytem , then . At the moment I am one loved-up Vettista . Now ,about that weather...........

 

[fatbloke-dim]

not much to report !

It's now mid January ,the 'Vette has been stood-down from active service until spring and better weather . The battery remains disconnected , but is still in fighting form when re-connected to start the car every 1-2 weeks . I let the engine get thoroughly warm , as warm as it can at idle , and shuffle the car back and forward using all the selector positions . It is not possible to get the battery tender hooked-up ,as although the car is still at home - can't find a garage - it would entail an extension lead from the house , thru' the front door letterbox , then thru' the porch door letterbox , and finally ,to keep things as weatherproof as poss , up under the car into the engine room . Can't see my missus going for that ! I did run the car out prior to taking it out of use , the slight misfire and burping was apparent under partial load , but was absent after a mile or two , and under a full-boot low-gear start no probs were manifest . So , tempting fate , it seems all is fixed , the new ECM and battery has done it , the car is reliable and a joy to drive . I had many good runs out during the freak warm spell ,and now I'm fully confident in the car . It's a good feeling . There are 2 questions remaining , not causing any issues other than curiosity . These being ;-
1. Roughly how long , and what kind of driving will see the ECM re-learn completed ?
And, 2. Referring to the parasitic draw of current , I can't remember if I posted that the 270mA was down to the left headlight being "energised" , evidenced by a click/clunk from there when re-connecting the battery . It does'nt occur if the main lighting fuse is pulled . Is a drain like this common ? Or could there be something like a limit-switch or something out of adjustment or the like ? I must say , tho ' , the lights work great and smoothly pop up and stow ,to my childish satisfaction . Just been out to lift the cover , as it's currently clear blue skies and high pressure , but frosty at night , so the car will get a little chance to dry out , there was slight condensation under the cover ,but overall ,it's keeping better then I'd dared to hope for. Two of the local coppers were doing a walk-round of the neighbourhood advising on security issues , and came over to have a good drool over it . They were impressed , even pleasantly surprised it'll do 30 to the gallon at 70mph . So , other than that , not much to report . Big thanks go to all who have chimed in to advise , help ,and reassure . Another aspect amongst many that makes 'Vette ownership so sweet .
Happy and healthy 2012 to you all .
Nigel H.