Grid heater comes on when turning on lights.

[pwcracer]

Have a 99 Ram,  it was shutting down when I would turn on the headlights.   I determined that the 2 wires going to the grid heater relay is coming on with the headlights.    It is a orange/black and a yellow/black wire.  from a diagram, I see that this comes out of the ECM and triggers + 12 when the key is turned on depending on temp.   I am trying to trace these wires back to the ECM and having a tough time.   It looks as though the loom may go through the firewall and into the cab.   

 

 

[Tractorman]

Before pursuing any further, I would check all grounds for continuity.  Any single poor ground at the right ground connection could give you the symptoms you are describing.  Poor grounds are notorious for leading one astray when using a multimeter or a test light.  Poor grounds back feed voltage to unrelated circuits.

 

Since you have a monthly subscription, I think you have access to wiring diagrams here.  There is also a wiring modification called the WT Wiring Mod (or something like that) available on this site .  This mod deals mostly with ground wiring.  It is an important modification to do for the 24 valve trucks.

 

- John

 

 

[pwcracer]

I've cleaned up a few grounds, specifically the one under the batter (Left side) and a few more that I can find.    My thought was to get to the 2 wires as close to the ECM as possible and see if they are working at that point.   Kind of chasing my tail right now

 

 

[Tractorman]

6 hours ago, pwcracer said:

Have a 99 Ram,  it was shutting down when I would turn on the headlights. 

 

Are you saying that an idling engine dies when you turn on the headlights?

 

6 hours ago, pwcracer said:

 I determined that the 2 wires going to the grid heater relay is coming on with the headlights

 

Even if the grid heaters are activated when the headlights are turned on, the engine still should not die.  Can you be more specific about the symptoms your truck is having?  Such as:  How long has this problem been occurring? Does it occur every time? Did the problem start occurring just after any other repairs were done?  What is indicating that the grid heater are on?  Is the engine warm or cold when this happens?  Etc.

 

- John

[wil440]

There's 2 grounds below the drivers side battery, I had a corroded wire right in the middle of one of those grounds and every time I indicated left the wipers would come on

 

I removed the battery to get a better look at both of them and missed it the first time as it was right in the middle of the crimped bunch with just one strand of wire still connected and that was green and festered.

After checking everything I removed the battery again and dug into  both and found it, soldered a new terminal on both of them, cleaned the body and job done

 

Not saying those are your problem just pointing out that what looks good sometimes isn't

[pwcracer]

Funny you should say that,   The original owner cleaned the ground under the battery, and I cleaned it further on tuesday.   Also added another ground to that location from the - bat post.    Still had odd issues.    Yesterday I decided to replace the ring connector on the wires, and 3-4 wires broke off.   I cut them back a couple inches and crimped them into the new connector.    Like magic, things are working again!

 

[Tractorman]

@pwcracer, thank you for letting the forum know the cause of your problem.  Your documentation once again shows the value of performing a voltage drop test.  A ground connection that appears to be good visually and is tight mechanically does not necessarily mean that the connection is good enough to handle the electrical current passing through the connection..  

 

For anyone interested, @Mopar1973Manhas written an article about the benefits of voltage drop testing and how to perform the test.  One of the best things about performing this test is that the test is performed BEFORE disturbing the electrical connection in question.  The results of voltage drop testing are always accurate.  

 

- John