  Observations of cooler atmospheres of super-Earths and Neptune sized objects
often show flat transmission spectra. The most likely cause of this trend is
the presence of aerosols (i.e. clouds and hazes) in the atmospheres of such
objects. High-resolution spectroscopy provides an opportunity to test this
hypothesis by targeting molecular species whose spectral line cores extend
above the level of such opaque decks. In this work, we analyse high-resolution
infrared observations of the warm Neptune GJ 3470 b taken over two transits
using CARMENES (R $\sim$ 80,000) and look for signatures of H$_2$O (previously
detected using HST WFC3+Spitzer observations) in these transits with a custom
pipeline fully accounting for the effects of data cleaning on any potential
exoplanet signal. We find that our data are potentially able to weakly detect
($\sim3\sigma$) an injected signal equivalent to the best-fit model from
previous HST WFC3+Spitzer observations. However, we do not make a significant
detection using the actual observations. Using a Bayesian framework to
simultaneously constrain the H$_2$O Volume Mixing Ratio (VMR) and the cloud top
pressure level, we select a family of models compatible with the non detection.
These are either very high VMR, cloud-free models, solar-abundance models with
a high cloud deck, or sub-solar abundance models with a moderate cloud deck.
This is a broader range compared to published results from low-resolution
spectroscopy, but is also compatible with them at a 1$\sigma$ level.
