Headlight relay - installed, but no lower beam driver's side

Larry

True Classic
I finally installed the Bob Brown headlight relay kit I bought from him last century. I'm 99.999% sure I followed each step, but my driver's side low beam doesn't work. The driver's side high beam does as does the passenger side low and high beams.

I tried the 9-volt battery test on the driver's side and the headlight turns on with the high beam switch off and on.

I'm unsure as to what to look at next. If the headlight works with the 9-volt battery attached, what would be the next thing to check?

Thanks,

Larry
 
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lookforjoe

True Classic
How did the wiring go? Schematic?

"I tried the 9-volt battery test on the driver's side and the headlight turns on with the high beam switch off and on."

What about the low beam, or is that what you meant?
 

Larry

True Classic
How did the wiring go? Schematic?

"I tried the 9-volt battery test on the driver's side and the headlight turns on with the high beam switch off and on."

What about the low beam, or is that what you meant?
Sorry... that's the test that is shown on the instructions and I explained the problem wrong...

I think trying to explain what I'm doing made it click (like a relay) in my head. I'll go futz with it a bit....
 

Larry

True Classic
How did the wiring go? Schematic?

"I tried the 9-volt battery test on the driver's side and the headlight turns on with the high beam switch off and on."

What about the low beam, or is that what you meant?

Ok. That didn't work.

I'm working with Bob Brown (most excellent) Headlight Relay kit.

I ran a 30A fused wire directly from my battery to the passenger side headlight pod. That went to the pair of relays mounted there. I ran another 30A fused wire across to the driver's side headlight pod.

Bob's troubleshooting says:

"You can test the operation of the headlight mod using a common 9-volt transistor radio battery....with everything hooked up *except the H4 Male plug* connect one side of the 9V battery to the pin with the Black (common) wire and the other side of the battery to a Green or Gray wire (activates high & low beams). The headlight should illuminate appropriately. If not, check your power connection(s) for a proper 12 volt supply and check the integrity of your ground. The 9-volt battery simply activates the appropriate headlight relay.

My issue is that on the driver's side, the low beam doesn't work but the high beam does. Both lights on the passenger side work fine. I swapped the relays on the driver's side and the problem persists that the low beam doesn't work but the high beam does.

If nothing worked on the driver's side, then the 9-volt battery test would reveal that it's either a power or a ground issue. But the fact the high beam works but not the low beam is confusing.

Before I put in the relays, the driver's side headlight worked on high and low beam.

I swapped in a new bulb and get the same results. True, it could be 2 bad bulbs but that seems a little less iffy to me so I'm assuming it *must* be something else.

Looking for suggestions of what could be the problem.

Thanks,

Larry
 

ng_randolph

Bjorn H
When you connect the 9V battery between the pins for the BLK and the GRY/BLK wires, do you hear/feel the relay click?

It usually does not matter, but just on the the off chance that your relays have protection diodes across the coil, make sure the battery negative goes to BLK.
 

Larry

True Classic
When you connect the 9V battery between the pins for the BLK and the GRY/BLK wires, do you hear/feel the relay click?

It usually does not matter, but just on the the off chance that your relays have protection diodes across the coil, make sure the battery negative goes to BLK.
Yep. I hear / feel the relay click.

And the battery negative goes to black. This was the Bob Brown Headlight Relay kit he manufactured over the years....
 

ng_randolph

Bjorn H
If you remove the low-beam relay, you should be able to measure full battery voltage between body ground and either terminal 30 or terminal 87 of the relay socket (I have not seen the BB harness, and I don't know which way it is wired). If you don't, there is an open in the battery feed to the relay socket. If you do see battery voltage on either #30 or #87, check continuity between the other (#87 or #30) terminal of the relay socket and the low beam contact on the plug that connects to the headlight. You should find continuity, and if you don't there is an open in that connection.

Bosch relay terminal numbering for reference.
 

lookforjoe

True Classic
Bjorn fault tracing guide should get you there.

If the low beam (gry/blk trigger) relay is clicking, then the problem has to be in the wire connection at 30 or 87 - the power feed and the power output to the bulb.

Since I'm a visual learner, I looked fora pic of it to help visualize the troubleshooting. This is the only pic of it I can find online.
Screen Shot 2021-02-20 at 8.58.57 AM.png
 

Larry

True Classic
If you remove the low-beam relay, you should be able to measure full battery voltage between body ground and either terminal 30 or terminal 87 of the relay socket (I have not seen the BB harness, and I don't know which way it is wired). If you don't, there is an open in the battery feed to the relay socket. If you do see battery voltage on either #30 or #87, check continuity between the other (#87 or #30) terminal of the relay socket and the low beam contact on the plug that connects to the headlight. You should find continuity, and if you don't there is an open in that connection.

Bosch relay terminal numbering for reference.
Thanks. I've got a screeching dryer to pay attention to, but I'll try to get to this soon. In the meantime, my fix is to drive with the high beams on - the car is lower than other cars and compared to Xenon and LED bulbs, even though they're H4 Halogens, they're probably not as bright.
 

Larry

True Classic
Bjorn fault tracing guide should get you there.

If the low beam (gry/blk trigger) relay is clicking, then the problem has to be in the wire connection at 30 or 87 - the power feed and the power output to the bulb.

Since I'm a visual learner, I looked fora pic of it to help visualize the troubleshooting. This is the only pic of it I can find online.
View attachment 43277
The low beam relay isn't clicking - just the high beam relay....
 

EricH

Eric Hamilton
Moderator
The low beam relay isn't clicking - just the high beam relay....
Without the relays.... that is in the original configuration with the wiring harness connector directly attached to the light instead of to Bob's (superbly made, BTW - I'm using two of them) does that low-beam light work? Check the fuse for that low beam. If the battery test works but the light doesn't work with the headlight switch, it usually means that that the headlight switch isn't telling the relay to turn on.
 

lookforjoe

True Classic
The low beam relay isn't clicking - just the high beam relay....

The most likely culprit, IMO is the female terminal connection at the headlamp bulb socket, that the BB harness plugs into. The terminals overheat with age as the connection deteriorates.
Since you have no click from the relay, that would indicate the low beam feed wire is not triggering the relay.
I think the left low beam is the grey wire, with grey black being the high beam. Unplug the BB harness from the headlamp connector & examine the terminal for signs of deformation/discoloration, etc. Take a pic if you can.

Here's a pic of mine before I replaced it with a ceramic connector, you can see the high beam wire disconnected from it's spade terminal

Dallara-Headlamp00024.jpg



this is what the terminals look like (internet pic)

Screen Shot 2021-02-23 at 7.37.55 AM.png
 
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