bigtim2001

My 2000 RX 300 seems to have a 2 volt drop from Driver to passenger side DRL bulbs. Using standard 9005 bulbs and grounds look good. Also high beam circuit and bulbs are working fine. Has anyone come accross this problem b4?

Any help would be greatly appreciated !

manianac

I'm trying to understand your query. There's a voltage drop of 2v on the wire between the two bulbs? Or there is a 2v difference? You do realize the DRLs are your hi-beam headlights in series to keep them dim?

Anyway when the DRLs are on, both hi-beams are in series, and there is also a resistor in-line with them (on USA models, Canada models there's just a jumper). Its possible you're measuring the voltage drop on the resistor, or available voltage at the bulbs.

bigtim2001

Thanks for responding manianc,
I know the DRL bulbs are the high beams as well. The problem I have is when the DRL's are on, the passenger side is dim compared to the drivers side. So I took a volt meter and probed the socket while in DRL mode and got a voltage reading of 6.4v dc on drivers side and 4.4 v dc on the passenger side. Tryng to figure out why available voltage at driver side higher than passenger side. Or should they be equal when DRL circuit is on.

When I do use the high beams, the bulbs are of equal brightness.

salimshah

I have never tried to verify the intensity of each of the bulbs in Day-light-running mode. I have always assumed 1/2 voltage on each.

The case you present is interesting as
6.4 + 4.4 = 10.8

So what is your battery voltage ... lets assume 12.5

The unaccounted voltage is 12.5 -10.8 = 1.7v ---> can we attribute that to wire loss and relay contact loss? [and resistor**]

If they were strictly a series connection (this is what we expect) then the voltages across each bulb must be the same (may not be Vbatt/2 due to wire loss and resistor **) and if the hot filament resistance is identical then the voltages should be exactly the same.

Without looking at the wiring diagram, my knee jerk reaction is that the filament hot resistance is not the same on the bulbs and that is causing dissimilar voltages.

A simple test ... swap the two bulbs ... would verify my assumption ... the voltages would walk with the bulbs. Check the make and wattage stamped on the bulbs.

Please note ... all of the above is based on analysis of the data without looking at the wiring diagram.

Salim

ps: Note the voltage across the bulbs is not being supplied and it is due to the current flow through the filament. In series circuit the current is the same in each filament.

manianac

Here's the wiring diagram.

As you can see, it does go through both bulbs and the resistor in series. If you're in fact measuring available voltage with the negative lead on a good ground, you should have 12v at pin 2 of the LH bulb, a lesser reading (but the same at both pin 1 of both bulbs), and lesser still (but not zero), at pin 2 of the RH bulb. See the aforementioned diagram for what I'm explaining, but basically all your measurements seem correct if you're measuring at pin 1 of the LH bulb and pin 2 of the RH bulbs, so try swapping them as salimshah suggested.

Also salimshah, I would attribute the 1.7v remained to the contact losses and wiring as you said, but with the resistor as well being a majority of it.

bigtim2001

Thank you manianac and salimshah !

Went back to the start and checked battery voltage which was 13.5v, turns out my LRS put 2 different bulbs in my DRL's so I started to play with the combinations. Depending on where you put the different bulbs which varied from H2 to H3 lenses vs. 60 and 65w bulbs it made a huge difference.

What I found in my particuler model was anything over an H3 60w bulb throws all the readings out of whack. I could test voltage at the connectors depending on which bulbs I used varying 2 plus volts on either side depending on the bulb combination I used. So what I ended up doing was getting a matched set of 9005 H3 60w bulbs and it corrected the problem. I assume it was the built in resistor used is designed to work with the 60w bulb combo. As salimshah said it was a resistance issue. Now all is well and working fine!!

While I still have your attention I am also trying to track down why my tailight bulb warning light won't go out. I have changed the third tailight bulb per the forum discussions but still unable to correct the issue. What I have noticed is the wire connections 0n the 7443 bulbs in the tail/stoplight bulbs is a graying of the bulb glass and a discoloration of the wire at the bulb itself where it makes contact with the factory socket.

Any thoughts on that ???

Thanking you both again for your time and help,

Tim