Why does my Hummer H3 have wet carpets and weird electrical problems?

Short answer: On the H3, random electrical gremlins (no-start, the AC jumping to full heat, wipers turning on by themselves, odd codes) are often caused by water getting inside. Owners traced it to clogged sunroof drain tubes or an AC evaporator drain that wasn't draining, which let moisture reach the body control module (the computer that runs many electrical features) and wiring. Clearing the drains and drying things out fixed it for them.

Symptom: Damp or soaked carpet (often worse on the passenger side), no-start or anti-theft problems, the AC or wipers acting on their own, or body codes such as B0790, B2725 and U1017.

What to check first

1. Pull up the carpet edges and feel underneath, especially on the passenger side.
2. Check the sunroof drain tubes. Pour a little water into the sunroof channel and see if it drains out under the truck.
3. Make sure the AC drips water under the truck on a humid day. If it doesn't, the evaporator drain may be clogged.
4. Look for white crust or corrosion on connectors and grounds under the carpet.
5. Check your VIN for recall 15V421 (blower motor connector).

Likely causes

1. Clogged AC evaporator drain wetting the body control module. A Hummer Forums owner chased no-starts, shutdowns and random AC and wiper behavior. The cause was AC condensation that wasn't draining. A can of evaporator cleaner cleared it.
2. Blocked sunroof drain tubes. Owners say the drain openings are small and clog. They cleaned or enlarged them, or rerouted them.
3. Corroded grounds or connectors from past water. An owner with a wet 2010 H3 found white crystals on wiring along with several body and network codes.

What it usually costs

I couldn't find a reliable published price. Clearing drains is cheap. Corroded wiring or a damaged module costs more, depending on how far the water got.

Is it safe to keep driving?

Usually drivable, but random shutdowns or a no-start can strand you, and wet wiring gets worse over time. Fix the leak and dry it out soon. Verify with a mechanic.

DIY or shop?

DIY for drains. Shop for corroded wiring or module replacement.

Recalls, bulletins and complaints in plain words

• No recall covers water leaks on the H3.
• Recall 15V421 (2006–2010 H3): the connector that controls the HVAC blower speed can overheat. Dealers replace part of the connector and wiring. If your truck is part of this recall, the dealer fixes it for free.
• NHTSA complaints: 53 keyword-matched complaints for Hummer H3 2006–2010 (of 800 unique complaints queried, NHTSA complaints API by model year, queried 2026-10-17; keywords: water, flood, sunroof, wet, moisture, soaked, carpet).

What owners report

• In H3 electrical issues finally fixed, a 2007 owner went through anti-theft no-starts, shutdowns, the AC jumping to full heat and wipers turning on by themselves. After grounds and other parts didn't help, he found the AC evaporator wasn't draining and moisture was shorting the body control module. Evaporator cleaner fixed it.
• In Typical Hummer flooding / electrical issues, a 2010 owner found water on both floors, codes B0790, B2725 and U1017, and white crystals on wiring. Members pointed to clogged sunroof drain tubes.

My take

My advice as a former detailer: a musty smell and water stains under the passenger mat tell you to check the drains before anything else. Do that on any used H3 before you buy it.

Vehicle focus: 2006–2010 Hummer H3.

Safety / mechanic note

Random shutdowns can happen in traffic. Verify with a mechanic.