When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I responded to another forum members posting seeking information relating to automatic headlight timing circuit...which is controlled by Body ECU in 1998+ LS400 multiplexed system circuit.
A timing circuit typically works with a resistor and capacitor, the latter having age related issues.
The ECU issue has pretty well been covered, however little information on age degradation of capacitors in numerous control modules and ECU's (other than engine ECU ).throughout the vehicle.
My immediate interest is in the body ECU....it controls a lot of systems. (Multiplexing permits control of numerous systems with significantly less wiring...of course it eliminates redundancy, so if one system is down, so too others). All of these systems work in a multiplexed system in concert with Body ECU.
Anyone care to share circuit board images of Body ECU depicting capacitor capacitances, Series (brand) and voltages?
Timing ckt could be based on simple basic R-C design or it could be more likely by such as flip flop, counter chip ckt. High value low voltage polarized caps. are usually on PCB voltage rails. Or at Vcc pins on chips for bypassing purposes.
A timing circuit typically works with a resistor and capacitor, the latter having age related issues.
Do you believe that Denso's engineers design circuits using that old technique? They usually use counters to decide timings.
Electrolytic capacitors reduces the capacitance in accordance with the Arrhenius equation but those engineers know it well and they design circuits aiming to last as many years as other major mechanical parts. On the other hand, QAS capacitors don't follow the Arrhenius equation and fail much quicker than conventional electrolytic capacitors. QAS capacitors for auto mobiles were designed to last longer using specially coated legs and special rubbers and were expected that the life span was almost the same with conventional ones. But the actual situations were not so. The condensation of the liquid caused too strong alkali inside and the severe corrosion started causing the leakage. That is the reason why so many main ECUs fail quicker than others. As long as I know, QAS capacitors were only used at the main ECU.
A fox is not taken twice in the same snare and there are no birds in last year's nest.
Do you believe that Denso's engineers design circuits using that old technique? They usually use counters to decide timings..
Analogue vs. digital. Accuracy, reliability, cost, digital timer wins. I retired at the turn of century which is already almost 20 years ago. Now there ought to be many more timer chips, ASICs for certain applications.
Analogue vs. digital. Accuracy, reliability, cost, digital timer wins. I retired at the turn of century which is already almost 20 years ago. Now there ought to be many more timer chips, ASICs for certain applications.
Does anyone have images of Body ECU circuit board to make this determination? Thanks.
Analogue vs. digital. Accuracy, reliability, cost, digital timer wins. I retired at the turn of century which is already almost 20 years ago. Now there ought to be many more timer chips, ASICs for certain applications.
+1.
You know things well although you have retired many years ago. I hope posters are like you. Recently I find some people here who are totally different from you.
+1.
You know things well although you have retired many years ago. I hope posters are like you. Recently I find some people here who are totally different from you.
Actually if cap. were causing the problem whoever having the problem of delayed light off, take the ECU out. Replace all the caps. Anyone can do this with decent soldering skills. Tip, using higher voltage rated one is OK, cap value does not have to be exact. It is OK to use equal value one or little higher than equal valued ones. Caps. does not cost much. Hope it is not the relay contacts stuck problem. Or we can wire in 12v powered time delay relay module in series with wire supplying 12V power to lights. Good spot to add this module would be at the fuse box. Some times bad caps are readily visible for unusual bulging. You can check caps properly with ESR meter.(better than using multi meter) One thing basic theories never change. If digital circuit is used probably it is NE555 chip based.
One more thing this type of caps are polarized. When replacing, watch the lead's marking. - to ground, + to the live circuit. Heavy black strip on the cap body points to the - (negative) lead. If leads are swapped cap will act like a piece of wire (in another word, direct short)
11-08-17, 07:27 PM
Body ecu capacitors
