Power Hungry
Member
You may or may not have seen the recent post on this and other forums regarding issues with [cheap] HID headlamps causing interference with the communications between the PCM and a specific multi-position chip. What concerns me (and I'm sure I'm not alone on this) is that a vehicle stalling as the result of electrical interference from an external source is a significant safety problem. Instead of blaming the HID headlamps, which don't seem to have any adverse effects on any other electronics systems in the vehicle, maybe someone should actually take a closer look at why the issue seems to be isolated specifically to the chip in question.
As originally posted by the vendor in question:
Let's break it down like a fraction and take a closer look at this to see if we can isolate some areas of concern...
The switching unit does contain a small micro-controller to handle switching and display functions. However, the output to the chip isn't really any different than that of a mechanical switch. There is a signal applied to any combination of 4 pins arranged in a binary format (4 pins = 16 positions) to achieve proper switching. Anti-bounce logic allows both styles of chips to change between positions seamlessly, with the only significant difference being that the digital switch style will delay changing output until the buttons have been in a quiescent state for about 500ms. The switching unit gets its power from the CHIP, not from the ECM directly. The chip itself gets its power from the J3 port on the ECM.
I have concerns with this. First, both the chip and switch do NOT run on 12V, but rather 5V. The argument that the "power source" to the chip or switch is dropping below sufficient voltage is not feasible because if this were the case, the PCM itself would have shut down already. In fact, during cranking the PCM can often see voltage dip below 9V. Historical bench testing of the EEC type PCM shows that the PCM is actually stable and functional (even during a reprogramming session) all the way down to about 7.5V, with the J3 port (the chip port) maintaining a stable 5V output... which incidentally where the chip gets its power from.
Does anyone have any idea what the current draw is from a set of HID headlamps? I don't have the specs from any specific kit, but it's obviously not enough to shut the ECM down, so why should it affect a chip? The only improvement gained by moving the HID controller to the passenger side headlamp is to change the ground location as the driver's side headlamp assy. shares a ground with the ECM.
Now we get to the root of the problem. We are NOT dealing with a power issue, but more specifically an RFI issue. Standard practice for digital signal cables which operate in noisy environments is to use single-termination shielded signal cables. The use of unshielded, flat-ribbon cable is just begging to introduce RFI into a given system. Ferrite chokes are one way to help improve against RFI, but shielded cable would pretty much resolve the problem completely. The reason that HID headlamps cause a problem is not the current draw, and not always poor grounding (though it sometimes is), but the fact that the HID controller produces a high voltage, AC current to excite the lamps. This conversion from DC to AC creates a significant amount of feedback and any systems not properly shielded can suffer interference.
I was not aware that the HID police were monitoring the forums. You know, non-CARB certified chips are illegal for sale or use in California, but I don't see anyone offering that information.
What it comes down to... Instead of complaining about crappy HIDs, just spend an extra $2.00 and supply a better shielded cable.
As originally posted by the vendor in question:
Let's break it down like a fraction and take a closer look at this to see if we can isolate some areas of concern...
The switching unit does contain a small micro-controller to handle switching and display functions. However, the output to the chip isn't really any different than that of a mechanical switch. There is a signal applied to any combination of 4 pins arranged in a binary format (4 pins = 16 positions) to achieve proper switching. Anti-bounce logic allows both styles of chips to change between positions seamlessly, with the only significant difference being that the digital switch style will delay changing output until the buttons have been in a quiescent state for about 500ms. The switching unit gets its power from the CHIP, not from the ECM directly. The chip itself gets its power from the J3 port on the ECM.
I have concerns with this. First, both the chip and switch do NOT run on 12V, but rather 5V. The argument that the "power source" to the chip or switch is dropping below sufficient voltage is not feasible because if this were the case, the PCM itself would have shut down already. In fact, during cranking the PCM can often see voltage dip below 9V. Historical bench testing of the EEC type PCM shows that the PCM is actually stable and functional (even during a reprogramming session) all the way down to about 7.5V, with the J3 port (the chip port) maintaining a stable 5V output... which incidentally where the chip gets its power from.
Does anyone have any idea what the current draw is from a set of HID headlamps? I don't have the specs from any specific kit, but it's obviously not enough to shut the ECM down, so why should it affect a chip? The only improvement gained by moving the HID controller to the passenger side headlamp is to change the ground location as the driver's side headlamp assy. shares a ground with the ECM.
Now we get to the root of the problem. We are NOT dealing with a power issue, but more specifically an RFI issue. Standard practice for digital signal cables which operate in noisy environments is to use single-termination shielded signal cables. The use of unshielded, flat-ribbon cable is just begging to introduce RFI into a given system. Ferrite chokes are one way to help improve against RFI, but shielded cable would pretty much resolve the problem completely. The reason that HID headlamps cause a problem is not the current draw, and not always poor grounding (though it sometimes is), but the fact that the HID controller produces a high voltage, AC current to excite the lamps. This conversion from DC to AC creates a significant amount of feedback and any systems not properly shielded can suffer interference.
I was not aware that the HID police were monitoring the forums. You know, non-CARB certified chips are illegal for sale or use in California, but I don't see anyone offering that information.
What it comes down to... Instead of complaining about crappy HIDs, just spend an extra $2.00 and supply a better shielded cable.
