Battery Temp Sensor question

[JAG1]

55 minutes ago, Mopar1973Man said:

 

Diodes are junk. Shouldn't be any connection between the case and the BATT + stud. That is a short to ground. 

 

Correct for the grid heaters relays. It should be infinite ohms on the two large studs. The two smaller studs should have a ohm reading. 

I was sure when diodes go or burn out that it doesn't mean the alternator is shorted to ground, both alternators got smokin' hot.  Not sure, but I think from running full tilt for an extended amount of time trying to replenish batteries getting drained that in in full 'sink' from high load.

 

 

Edited February 4, 2021 by JAG1

[Mopar1973Man]

21 minutes ago, JAG1 said:

I was sure when diodes go or burn out that it doesn't mean the alternator is shorted to ground,

 

Yes it does! It very possible to short to ground on the diodes hence why the melt and blow out. This diode pack off a ND did exactly that and shorted to ground and burned up. 

 

[JAG1]

Wow! @Mopar1973Man does a short like that cause further damage to the alternator that you cannot change just the diode bridge and place it back into service?

 

 

Edited February 4, 2021 by JAG1

[Mopar1973Man]

3 minutes ago, JAG1 said:

Wow! @Mopar1973Man does a short like that cause further damage to the alternator that you cannot change just the diode bridge and place it back into service?

 

Possible it all has to do with how long the high current continues. If the windings overheat either the field and/or the stator and burn the coating it can cause winding damage. That's how my field failure occur the armature or field winding over heated shorted the blue lead to ground and POOF went the PCM. Remember either side shorts out damage can occur period. Hence why I've got the 150 A circuit breaker and the 5 A field lead fuse now. 

 

Any rate if there is any heat that is too hot to touch the alternator then you have issues and should have the alternator tested. Most likely already failed or going to fail.

[JAG1]

8 minutes ago, Mopar1973Man said:

 

Possible it all has to do with how long the high current continues. If the windings overheat either the field and/or the stator and burn the coating it can cause winding damage. That's how my field failure occur the armature or field winding over heated shorted the blue lead to ground and POOF went the PCM. Remember either side shorts out damage can occur period. Hence why I've got the 150 A circuit breaker and the 5 A field lead fuse now. 

 

Any rate if there is any heat that is too hot to touch the alternator then you have issues and should have the alternator tested. Most likely already failed or going to fail.

I knew both failed alright both were smokin, now need to find out why, hence doing further testing on the relays today. When using a fluke ohm meter.... is the meter so sensitive that having 3.5 ohms resistance is what the probes crossed by themselves read?

 

U know those grid heater relays should fail in the open position..... I think that is what is so confusing, but I guess they weld themselves shut sometimes. Don't understand the clicking yet they show they are closed when not activated

Edited February 4, 2021 by JAG1

[Mopar1973Man]

Just now, JAG1 said:

When using a fluke ohm meter.... is the meter so sensitive that having 3.5 ohms resistance is what the probes crossed by themselves read?

 

No that is poor meter or leads. It should show 0.00 ohms probes touching. On fluke meter there is a diagnostic test you can do look on your manual or look up the manual for your Fluke. 

 

This the RV truck or the work truck?

 

If its the RV you should look into battery isolation block. These are typically diodes wired into the charge line for one to the engine battery and then one lead to the RV battery. These tend to work great because of no relays and weak connections. 

 

Either truck you should be doing the voltage drop test for you main feed lines even the alternator charge lines.

 

[JAG1]

1 hour ago, Mopar1973Man said:

 

No that is poor meter or leads. It should show 0.00 ohms probes touching. On fluke meter there is a diagnostic test you can do look on your manual or look up the manual for your Fluke. 

 

This the RV truck or the work truck?

 

If its the RV you should look into battery isolation block. These are typically diodes wired into the charge line for one to the engine battery and then one lead to the RV battery. These tend to work great because of no relays and weak connections. 

 

Either truck you should be doing the voltage drop test for you main feed lines even the alternator charge lines.

 

It's the work truck that cooks the alternators. I think it's from the grid heaters. Doing a search I found out about a bolt that comes loose from the isolation insulator deteriorating then shorts to ground and melting the bolt head off and the bolt drops into the intake. (no matter what you think.... no, I did not design that), but its the bolt that holds the power lead to the intake grid heaters.

[Mopar1973Man]

Just replace the grid heater if the power studs are damaged. Don't mess around with something like that. Grid heater are fairly cheap.

[dripley]

11 hours ago, JAG1 said:

It's the work truck that cooks the alternators. I think it's from the grid heaters. Doing a search I found out about a bolt that comes loose from the isolation insulator deteriorating then shorts to ground and melting the bolt head off and the bolt drops into the intake. (no matter what you think.... no, I did not design that), but its the bolt that holds the power lead to the intake grid heaters.

One of the reasons I disconnected mine was due to one of the insulators on bolt was partially melted. Not alot but enough to make wonder what was happening. So I just disconnected them to be safe.

[JAG1]

Bought new grid relays tonight. $80 bucks at Oreillys'. Got home and tested/ placed ohm meter on them, not installed yet and yes voltmeter shows OL like it should. So yes my old grid heater relays are both bad, causing full tilt and smokin two alternators. lucky too that my PCM is in good shape didn't burn in either episode. 

 

It is unfortunate the grid heater relays fail in the closed position. Thats a bad deal. Im hoping someone has a solution to this problem as we have been occasionally hearing about shorted alternators.

 

BTW everyone, if both batteries were strapped the way W-T says the temp sensor would have indeed limited the output on the alternator. As it is the temp sensor is not able to see what is happening with the passenger battery so you have to double strap for it to work. Sorry Mikey Mopie you owe me BIG milkshake for that one. Remember that with MoparMom? that was a very good time we had together. She was the best person around. 

Edited February 5, 2021 by JAG1

[Mopar1973Man]

7 hours ago, JAG1 said:

 

BTW everyone, if both batteries were strapped the way W-T says the temp sensor would have indeed limited the output on the alternator.

 

Absolutely will not... It will not limit the output... Remember I've got this huge 1,000 pound battery system here and it did NOT protect it when 1 cell went bad. Still cost me $4,800 replace all batteries and the only way to fix it is not battery temp sensor but replace the batteries. 

[Dieselfuture]

7 hours ago, JAG1 said:

Im hoping someone has a solution to this problem as we have been occasionally hearing about shorted alternators.

Put relays on toggle switch, I'm using push button switch so I don't forget it on. Will probably make your grids last 100 times longer.

[Mopar1973Man]

1 hour ago, Dieselfuture said:

Put relays on toggle switch

 

Can't for smog controlled states being it will set the CEL and P0380 and P0382... This is why I unhook my grid heaters in April and leave unhooked till October. The power lead is right at the drivers side battery positive. Takes less than 5 seconds to deal with.

 

Most morning I don't even WAIT TO START I just hit the key and go. This winter has been super mild and not really gotten below 32*F for long. 

[Doubletrouble]

 I disconnected my grids over the summer as well. No point in wearing them out when not needed. 

 Probably gonna need them today though. Temp is 16° with wind chill of -7°. I need to have grid heaters in my coat!

[Mopar1973Man]

Back to the wiring... I know W-T has been floating around and keeps telling folks they NEED to parallel both ground and positives. This will not fix the problem. It will not stop a battery from boiling over either. Again if there is a problem with main cables make sure to load test them if there is over 0.2 Volt drop then those cables need REPLACEMENT. 

 

I've tested several truck using jumper cables and found ZERO change in parallel ground cables. There is ZERO GAINS. This will not fix a problem with a bad battery cell that is overheating. Again this is due to improper maintenance of the battery and not proper recharged. This is more common with city folks that drive very short distances. You draw out 500 to 700 Amp to start the engine cold than drive barely 5 to 10 miles and shut down then the batteries are still discharged. Again I find more that the OEM main cables are oxided in the jacket, bad terminal that are oxidized, or just plain bad batteries. 

 

Like my last Cummins I worked on here, I tested ground cables on had just a mere 0.003 to 0.005 (3 to 5 mVDC) voltage drop. Again with jump cables parallel between ground did NOT change the outcome of the test. 

[LorenS]

I think we all agree that charging the battery closest to the alternator is preferred, all else being equal.  So for those that care, would it make more sense to extend (relocate) the temp sensor to the passenger battery, versus running the charge wire across the engine bay - which W-T said was a stupid design.

Seems like a hole saw followed by attention with a small hand held router (for the small recess so sensor sits flush) would do the trick.

[Mopar1973Man]

4 minutes ago, LorenS said:

So for those that care, would it make more sense to extend (relocate) the temp sensor to the passenger battery, versus running the charge wire across the engine bay

 

No, it will not make any difference. If all cables are the same then the voltage is the same. Alternator will deliver equal voltage to both batteries. Moving the sensor will not change that out come because if cables have the same voltage the charge is the same. The batteries do make a difference if one has a shorted cell and the other doesn't. Regardless your back to the same problem the battery temp sensor is NOT a protection device but to set the charging voltage that's it. It will not protect a battery... 

 

When all the cables are equal then it up to the batteries to charge equally which both batteries will warm up the same. Like in my house battery bank I've got one temp sensor. It will not prevent the far left battery from temp swings again if the battery are all equal the temps are all the same TILL you have a battery or single cell that is shorted now that SINGLE battery or cell will get hot. It not the battery temp sensor job to throttle back because of a bad battery cell. It's up to the owner to replace his BATTERIES not move the sensor to attempt to throttle back for a dead cell. Not a good plan at all. 

[JAG1]

@Mopar1973Man are you talking about a shorted cell battery running down the others, and ruining them because that shorted cell has all the other batteries in parallel while in full sink?

There is a difference when talking about a controlled charge rate right? I'm asking here as I do not think the battery temp sensor is to only sense ambient temps from the weather, but actual battery temps.

I do not like that the grid heater relays fail in a closed position. That is....... and I repeat....... a bad situation. There is a way to stop the codes with a manual control switch (factory relays still in use) by fooling the PCM with resistors. Don't understand that fully yet. At any rate I sure would like relays to fail in the open position via different relays for example as the grid heaters need to alternate as the PCM commands. 

13 minutes ago, LorenS said:

I think we all agree that charging the battery closest to the alternator is preferred, all else being equal.  So for those that care, would it make more sense to extend (relocate) the temp sensor to the passenger battery, versus running the charge wire across the engine bay - which W-T said was a stupid design.

Seems like a hole saw followed by attention with a small hand held router (for the small recess so sensor sits flush) would do the trick.

Yes, W-T did say that would be okay also.

Mike in your case it is important to save all the other expensive batteries in your solar system bank when a shorted cell causes one bad battery to go into full sink and dead short, but I think we are more concerned with saving the alternators and in some instances from burning the PCM. There is a difference......... I'm also wondering what caused your alternator to short out. Did you ever check your grid heater relays?

 

I feel like I'm in Kindergarten swimming with some big professors here and they might turn into alligators, but this subject of saving our alternators and the PCM is important so it's okay if I get underwater a little it's worth the discussion even if I do not know everything here

Edited February 5, 2021 by JAG1

[Mopar1973Man]

6 minutes ago, JAG1 said:

@Mopar1973Man are you talking about a shorted cell battery running down the others, and ruining them because that shorted cell has all the other batteries in parallel while in full sink?

 

Yes. One example using your set up and failure points. So if you voltage drop test both cables (NEG) and there is 0.003 to 0.005 volt drop this means that the voltage to BOTH BATTERIES is with the alternator charging 14.5 volt will net you roughly 14.497 to 14.495 volts to both batteries not even going to notice. Battery temp sensor is only going to change the voltage between 13.2 volts to 14.8 volts period. It is not going to fix a bad battery or cable. The balance of the batteries is based directly on the condition of the cables if there is excessive voltage drop then you will be imbalance between batteries. Like I'm showing if the voltage drop in mere 0.003 to 0.005 volts you not going make zero difference moving the battery temp sensor. As the current flow on the positive cable its shared directly and equally to both batteries. 

 

The ONLY way not to be equal charge is...

• Bad battery with bad cell
• Bad cable(s) with more than 0.2 volt drop. 

So if you have a mag-lite flash light do you only replace one of the two AA batteries or do you replace both? Me I replace both. 

 

Again if you want to verify a change then use you jumper cables between two point and see if the voltage changes. Say for example the passenger NEG cable was bad and showed a 0.3 volt drop which is a failure. Now take a set of jumper cables and jump between the block and the passenger battery. You should see a +0.3 gain of voltage at the battery. Now that tells me exactly that passenger battery cable is BAD and requires replacement. Adding that parallel cable will ultimately mask this and the cable can fail and now stress the remaining driver side ground which is not and will start to fail from over current. This why I DO NOT suggest this parallel cable mod nor suggest moving the sensor which is not going to change the charging which is still set for between 13,2 in the summer heat to 14.8 in the dead cold winter.

[LorenS]

16 minutes ago, Mopar1973Man said:

If all cables are the same then the voltage is the same

But even if all cables are the same today, they won't be after awhile.  That's kind of the whole point of this.  I'd prefer my driver's batter be undercharged than my passenger side battery getting the life boiled out of it because the alternator is pumping the juice to it trying to overcome an (inevitable) bad connection.    We don't all live in the dry climate of Idaho where battery connections last millennia.

I do religiously check my cables based on your teachings so am not too worried about it, but for others, moving the sensor may make the most sense.