Hi everyone, this is my very first post on this forum. I come from a background in diesel Mercedes (W123s) and have done every job imaginable on those cars. I also have my grandpas 1964 Oldsmobile cutlass that I am restoring. Long story short, working on cars is nothing new to me and I'm glad to finally make an account here.

The issue I'm running into is that my 1988 Toyota's tail lights won't come on when I turn the stalk to the on position. The dash lights don't come on as well and I assume they are connected. This started a few months ago simply one day I turned my lights on and noticed the dash didn't light up. I reflipped the stalk and magically the dash lights came on. I figured it was a worn out switch but I was driving the other day right before dark and I had my lights on (the dash lights and tail lights weren't on as per the issue) and I shut my blower fan off and magically the dash lights turned on, as well as the tail lights.

I have owned this truck for about two years and have done a bunch of maintenance to it but I am not so well versed in these trucks just yet. So instead of going to town on the truck I figured I'd ask here first if anyone has any ideas. The fuse is fine so I presume there is a short somewhere or a corroded ground somewhere. I have no clue where to look first though.

Thank you

 

My bet is the tail light control relay, but it might well be the ground in the driver's side kick panel.

The ground is pretty easy to check. It's above the fuse block. There are many wires crimped together, and then crimped to the ground's ring terminal. Where the many-into-one crimp is has a known problem with loosening up, causing intermittent problems. A wiggle with the lights on will tell the tale.

The tail light relay is located just under the fuse block in the driver's side kick panel. The flasher unit for the turn signal is to the rear, the tail light relay is to the front. You can pull it and check it outside the truck.


Read between terminal 1 and 2. Should be close to a short. That's the coil. Between 2 and 3 should read open. Apply +12 VDC between terminals 1 and 2, the read ohms between 2 and 3. It should now be a short.



As usual, I may be wrong, but that's what it sounds like it could be to me, for what that's worth.
Good luck to ya! Welcome to the Forum, and to the Toyota Owners Club.
Pat☺

 

Easier to just put a test light to the test terminal of the "Tail" fuse. Do this when the switch is on but the lights aren't lit. If it has enough power to light a test lamp you know the switch is good, the relay is functional, and the B ground is good. Now you can wiggle test G at the kick panel.

 

I greatly appreciate the replies. I worked on the truck this afternoon and checked those grounds first. Some of them were slightly corroded but I sanded them and put them all back together. That didn't fix the issue but it was some good maintenance. Next, I pulled the tail light relay as mentioned above and I tested for continuity between terminal 1 and 2. No continuity. I double checked and then I figured I'd pull the relay apart to see if I could learn anything. I learned that you can't really fix these relays. I still wanted to verify that the relay was the culprit (thinking maybe I read the diagram wrong as my relay showed that same diagram albeit slightly different than the post above) so I bypassed the relay altogether:



These are the two terminals if anyone in the future is wondering:



Here is the fusebox with the relay removed and the terminals jumped:



Anyways, that did the trick and my tail lights and dash worked. I verified that there wasn't anything else wrong with the system. So I ordered a new relay for 5$ which should fix the problem overall. Obviously I won't keep those terminals jumped as that was only for testing purposes.

I hope this helps someone in the future and thank you to the two posters above that got me started.

 

Glad you got it!
Best of luck to you in future difficulties. There will be, in a 30+ year old truck, but they're well worth the effort. I've had my since they were nearly new, and I have no plans to give them up!
Pat☺

 

No continuity even with the coil energized, correct?
A jumper will keep tail light on even if ground path though dimmer-stalk-switch is broken. Pls check your other thread. I posted there.
Merry Christmas to all!

 

Thanks for all of the advice everyone.

The new relay came in the mail today. I popped it in and everything now works as it should: