map light wire shows 7.5 volts

Stereo, security systems, vehicle electronics, and electrical-related discussions
Post Reply
dougreed
Posts: 12
Joined: Mon Apr 12, 2010 12:40 am

map light wire shows 7.5 volts

Post by dougreed » Sat Jan 18, 2020 6:07 pm

I have an 06 base Vibe. My license plate bulbs burned out. I used my map light bulbs as I needed license plate illumination right now! Anyway, later I got bulbs and put them in my map light - no light. The map light previously did work, I turned them on to make sure the bulbs were good before I put them in the license light sockets. So, I tested the bulbs with jumpers at the battery - bulbs work. Hmmm. I took off the rear view mirror & unplugged the power wire. I tested the voltage in the wire & was only getting 7.5 volts! Hmmm. I turned on the car and retested - getting 8.5v now! I shut off the car, disconnected the battery for 30 minutes and retested - same results. I can find no blown fuses. Everything else is working fine. The map light was working just fine, now, IDK??? Any ideas? This is weird... Maybe I'll put the other bulbs back in and see if they work in there? Why 7 & 8 volts??? I really like Vibes. My daughter needed a good car so I sold her my 05, so I just HAD TO FIND another one!... Here's a good story. Had a ski boat with a nice Volvo Penta stern drive. Put it away in the fall, got it out in the spring, pushed the throttle forward and the boat went backwards! I ended up taking the stern drive apart and flipped the reverse ring over and then all was normal again! Is that crazy or what?!?!

jolt
Posts: 779
Joined: Sun Mar 02, 2014 2:07 am
Location: Twin Cities, Minnesota

Re: map light wire shows 7.5 volts

Post by jolt » Mon Jan 20, 2020 12:09 am

You measured 7.5 volt between the two points that you had the test leads hooked to. Try moving the ground lead of your meter to a different ground location (the dash frame) and see if the voltage changes. If the new reading is now above 12 volts, you have a bad ground. If voltage is still low, you need to start tracing the power side wiring back to find where the voltage drop is in your wiring, ie bad connection, bad wire.

Hopefully you are not trying to use LED replacements bulbs. If you are the bulbs must be installed with the proper polarity for the LED to work.

Speedwoble
Posts: 7
Joined: Tue Apr 09, 2019 7:04 pm

Re: map light wire shows 7.5 volts

Post by Speedwoble » Fri Jan 31, 2020 7:43 am

I have a similar problem. I shorted out the light socket when installing a bulb, heard a pop and smelled a whiff of electrical smoke. I measure 6-7V between the 2 wires at the connector to the rearview mirror, but 12V between the + wire and a good ground(the power port socket above the shifter)
This means I damaged the ground circuit. I have not tracked down where it is damaged it yet.

dougreed
Posts: 12
Joined: Mon Apr 12, 2010 12:40 am

Re: map light wire shows 7.5 volts

Post by dougreed » Sun Apr 19, 2020 7:18 pm

Thank you all. Yes I am using LED's. Have a lot of them in use. Yes, polarity check. Yes, believe I have a bad (-) wire, measures full v when I ground to chassis.

Speedwoble
Posts: 7
Joined: Tue Apr 09, 2019 7:04 pm

Re: map light wire shows 7.5 volts

Post by Speedwoble » Mon Jun 22, 2020 5:51 pm

Well, I tried to get the integration relay out to do proper troubleshooting after finding some detailed Toyota wiring schematics. It is a bear to reach under the lower dash, and it looked like it would be a lot of time to remove the lower Dash. So I took a break of a few months.

Meanwhile I found a complete fuse assembly with the Integration relay (82641 01070) on eBay for $40 shipped, so I went ahead and bought that.

I re-attempted accessing the old relay and found that by removing the plastic trim below the steering wheel and 2 of the 3 bolts holding the fuse assembly in, I was able to twist the fuse assembly for access and remove the old relay. I had to use an assortment of small screwdrivers to lift and separate the 5 different clips holding the relay in. I snapped in the replacement relay in and Voila! map lights work again.

I took apart the old "bad" relay and could not spot any failed components, but will look at it closer another day.

Post Reply