Lights dim/bright at certain rpm...

Hybrid96EK · Post by **Hybrid96EK** » Mon Sep 14, 2009 11:58 pm

Anyone know why the lights on my 96 hatch seem to dim/brighten at a certain RPM but only with OBD1 ECU? Seems fine with the OBD2 ECU, or perhaps I am not noticing it as much. Anyways, drives me nuts, was wondering if anyone else had this issue and perhaps found a solution?

thething96 · Post by **thething96** » Tue Sep 15, 2009 10:04 am

I had the same issue. At idle or light throttle, the lights were dim, mid to high throttle, lights were bright. My issue was the ELD, but maybe that's what the ELD is supposed to do................

relic1 · Post by **relic1** » Tue Sep 15, 2009 1:40 pm

^^ actually that's the voltage regulator. the lights get brighter and dimmer due to the alternator not keeping up with the demands of the car. This causes the voltage to rise and fall depending on the alternators output. the ELD functionality would be the ECU raising the idle RPM when the electrical loads increase enough to require more alternator output. (ie blower fan + wipers + headlights + etc) OP: I've seen this as well, especially when cruising at light throttle. No idea yet as to why it's doing it only with OBD1 ECUs. I need to drop back to Crome and see if it does it there also. Mine is sort of a dim pulse not really dim that's RPM dependant though... You may want to check your alternator belt, have your alternator checked and check your grounds. (RPM = vibration = loose connection finder)

Hybrid96EK · Post by **Hybrid96EK** » Tue Sep 15, 2009 11:16 pm

I checked the grounds last night. They were all tight. I think I am going to first try making all new grounds, then go from there..

greasemonkee · Post by **greasemonkee** » Wed Sep 16, 2009 5:43 pm

The ELD can be responsible for this. After going through 3 alternators on a customer's car last week, I realized the eld/ecu was cutting the rotor field voltage through the alt control line. After clipping that line, it charged like a normal car does and without the fluctuation.

thething96 · Post by **thething96** » Thu Sep 17, 2009 10:23 am

I figured it was an ELD issue because as soon as I disabled it, the lights became very stable...........................

relic1 · Post by **relic1** » Thu Sep 17, 2009 11:35 am

this goes against what I've understood about the ELD... I think I need to go back to the manuals and read more.

Hybrid96EK · Post by **Hybrid96EK** » Thu Sep 17, 2009 7:54 pm

thething96 wrote:I figured it was an ELD issue because as soon as I disabled it, the lights became very stable...........................

Thats what I was going to ask. Can't you just disable the ELD?

james25 · Post by **james25** » Sat Sep 19, 2009 6:57 pm

Hmm! I myself have this issue but somewhat got around it by just turning my interior blower fan on and leaving it on

see, if I don't do that my charging voltage drops just below batt voltage at idle but goes back up when the car starts to move. I think I'm going to try what greasemonkee posted.