Based on the Chevrolet Silverado 1500, the full-size GMC Sierra 1500 provides a more upscale truck experience than its sibling. It definitely is the more handsome of the two pickups, and it offers impressive powertrain options that allow it to take on big towing and hauling jobs.

Despite the GMC Sierra 1500‘s good points, though, some owners have had serious mechanical and quality issues with it with relatively few miles on their vehicles. Read on to learn more about the worst complaints before 100,000 miles that owners have submitted to CarComplaints.com.

Subpar lighting pattern

The 2015 GMC Sierra 1500 was plagued with 61 problems related to headlight beam patterns and related issues. Problems in this category accounted for almost a third of the problems submitted for this year and were found across multiple trim levels. The severity level for this problem was rated as pretty bad, according to CarComplaints.com

There were 53 problems reported in the poor lighting pattern subcategory. Owners described a variety of problems including the beam pattern not being wide enough, limited direction for the beam, overall beam dimness at night or in rainy conditions. 

A number of owners were unsure what caused the problem, and they sometimes didn’t receive any insight from GMC dealerships. Some owners had the headlight assembly replaced and others tried replacing the headlights or bulbs. In many cases, these approaches didn’t really solve the problem, even though the owners themselves had to shell out cash to have the work done or do it themselves.

Because defective headlights are a serious safety issue, the NHTSA received a total of 78 complaints for the entire problem category. Among them, one crash was attributed to the problem.

On average, owners had to pay $210 to try to fix the problem. The average mileage for the lighting pattern problem was a measly 8,650 miles.

A/C systems that blew hot air

Failing air conditioning systems posed persistent and serious problems for owners of 2015 GMC Sierra 1500 trucks. There were 31 reported problems for this year. Some owners weren’t sure how to solve the problem, while others had to replace the condenser, compressor, or the A/C line to the pump. A few owners had to have the compressors replaced twice. Some were forced to replace the entire A/C unit. 

While the number of problems for this category doesn’t seem like much, CarComplaints.com gave it a severity rating of pretty bad. The typical cost to repair the air conditioning system was $1,190, and the average odometer reading was 58,650 miles.

Some GMC Sierra models featured awful headlights

The 2014 GMC Sierra‘s headlight problem was another variation on the 2015’s. In this case, the situation was much worse, with 111 problems submitted. CarComplaints.com designated the problem category as really awful.

Of these problems, 106 were chalked up to terrible headlights and poor visibility. Owners said the headlights were not bright enough for night driving. Rainy conditions after dark also made inadequate visibility even worse. Running the truck’s high beams did not help in many cases, either.

About half of the owners weren’t sure what was causing the problem. Some said that they took advantage of a recall to have the headlight assembly replaced, and others had GM install the 2016 model year’s headlight assembly. A few upgraded headlights and others had the dealer replace the bulbs.

The typical repair cost for the problem was $430. But what is striking is that the average mileage for it was only 8,500 miles. A few owners had just purchased the truck when they noticed the problem. 

You should know that these three problems—the poor lighting pattern in the 2015 Sierra, the A/C not working for the same model year, and the 2014 Sierra’s terrible headlights—were bad enough that CarComplaints.com ranked them as the worst Sierra 1500 problems of all model years.

The 2014 GMC Sierra 1500 had 307 reported problems, which was the most among all model years. However, the 2015 model was rated as worse because of steeper repair costs and more issues with fewer miles on the odometer. All of this is useful information if you’re thinking about buying a used truck from these model years.