80 Series power windows are slow. On a cold morning they need a hand on the glass to make it to the top. Plug-in kits run about $265. I built my own on my 1990 HDJ81 for $128.92 in parts, and most of the kits have plenty left over.
/WHY 80 SERIES POWER WINDOWS ARE SLOW
Voltage drop. Current runs through the factory relay, the master switch contacts, a stack of connectors and 30-plus years of wiring. Each one eats some voltage before the motor sees it.
Worn or dry window channels add drag on top of it. Clean and lube them alongside this mod.
/THE DIY VERSION
Shed Maniacs, an Australian YouTube channel, built one for about $30 AUD on a 1991 80 Series. Their video is where this started. Credit to them.
I planned to go one better and build a locking plug out of a gutted factory relay. Then I tried their way, male blade connectors pushed straight into the socket, and it was easier and a lot faster. So I kept it.
The one thing I added is a fuse. Their diagram has none. Mine has a 25A inline fuse on the main feed.
/HOW IT WORKS
Key off, only the main feed is live, and it stops at the open relay. Key on, the ignition feed closes the relay, the module takes 12V in and puts 15V out, and the window switches get the higher voltage. With the key off, the module sees nothing, so it has no drain on the battery.
/80 SERIES POWER WINDOW BOOSTER PARTS LIST
| Part | Price |
|---|---|
| XWST 12V to 15V 15A step-up module, 225W, potted aluminum case, over-current and over-temp protection | $28.99 |
| iRhapsody 4-pin 40A relay with 12 AWG pigtail | $9.99 |
| Inline fuse holders, 12 AWG, 4-pack with 25A fuses | $7.99 |
| GS Power 12 AWG oxygen-free copper wire, 25 ft red and 25 ft black | $35.99 |
| Haisstronica heat shrink male blade connectors, 12 to 10 AWG, 100 pieces | $13.99 |
| TICONN heat shrink ring terminals and butt connectors, 120 pieces | $9.99 |
| Adhesive-lined 3:1 heat shrink tubing, 400 pieces | $13.99 |
| Alex Tech 1/4 inch braided sleeving, 25 ft | $7.99 |
| Total | $128.92, against about $265 for a plug-in kit |
Amazon prices as of October 2026. Most of the kits leave plenty over for the next job. Buy copper wire, not the cheaper copper-clad aluminum. On a run pulling close to 20A, aluminum eats the voltage you're trying to win back.
Check a blade connector in the socket before you crimp them all. It should push in snug.
XWST also sells a 30A version for $59.99. More headroom if you run two windows at once.
One caveat. The XWST listing rates the input at 9 to 13V. A running alternator sits around 14V. The seller never answered my question about it, so meter the yellow lead with the engine running before you call it done.
/80 SERIES POWER WINDOW RELAY LOCATION
The power window relay plugs into a socket under the driver side kick panel. On my RHD truck the driver side is the right.
Disconnect the battery first. The main feed at the socket is live with the key off.
/WIRING
Print it: download the wiring sheet as a one-page PDF. It has this diagram, the socket map, the wire list and a checklist for before it goes in.
With the socket viewed face on:
- Top left is ground. Run it to relay pin 85 and to both grounds on the module.
- Bottom left is switched ignition. Run it to relay pin 86.
- Bottom right is the main power feed. Run it through the 25A inline fuse to relay pin 30.
- Relay pin 87 goes to the module input, the red lead.
- The module output, the yellow lead, goes to top right. This slot feeds the window switches.
The fuse matters. At its full 15A output the module pulls about 19A from the battery. A 25A fuse covers the 12 AWG run with room to spare.
/CHECK THE SOCKET WITH A METER
Face-on diagrams get mirrored. Meter every slot before you connect anything.
- Key off, only the main feed shows 12V.
- Key on, switched ignition shows 12V too.
- Ground has continuity to chassis.
If your readings don't match the diagram, trust the meter.
/CONNECT AT THE RELAY SOCKET
- Pull the factory power window relay out of the socket and keep it.
- Crimp a male blade connector onto each of four 12 AWG leads, then shrink it.
- Push each connector into its slot, going by the wiring above and your meter readings.
- Run the leads in braided sleeving.
Going back to stock takes two minutes. Pull the four connectors and plug the factory relay back in.
/WIRE THE STEP-UP MODULE
The module has four leads: red and black in, black and yellow out. Bench test it before it goes in the truck. Put 12V on the red and its black, and meter the yellow. It should read 15V.
Bolt the module to metal. The aluminum case sheds heat into whatever it sits on.
/BUILD IT OR BUY IT
The DIY version costs $128.92 in parts and an afternoon with a crimper. A plug-in kit costs about $265 and 15 minutes.
More on the truck itself is in FJ80 vs FZJ80 vs HDJ81, and every service I've done on it is in my HDJ81 service log.
Kingston
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