diff --git a/html/admin.html b/html/admin.html
index 35b78ed..5e775e8 100755
--- a/html/admin.html
+++ b/html/admin.html
@@ -612,8 +612,23 @@ window.onload = function() {
                     // Compare RTC time with browser time
                       const alertContainer = document.getElementById("alert_container");
                       alertContainer.innerHTML = "";
+                      const rtcInput = document.getElementById("RTC_utc_time");
 
-                      if (response.rtc_module_time) {
+                      if (response.rtc_module_time === 'not connected' || !response.rtc_module_time) {
+                        // RTC module disconnected
+                        rtcInput.classList.add('border-danger', 'text-danger');
+                        rtcInput.classList.remove('border-primary');
+                        alertContainer.innerHTML = `
+                            <div class="alert alert-danger d-flex align-items-center" role="alert">
+                                <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" fill="currentColor" class="bi bi-exclamation-triangle-fill me-2 flex-shrink-0" viewBox="0 0 16 16">
+                                    <path d="M8.982 1.566a1.13 1.13 0 0 0-1.96 0L.165 13.233c-.457.778.091 1.767.98 1.767h13.713c.889 0 1.436-.99.98-1.767L8.982 1.566zM8 5c.535 0 .954.462.9.995l-.35 3.507a.552.552 0 0 1-1.1 0L7.1 5.995A.905.905 0 0 1 8 5zm.002 6a1 1 0 1 1 0 2 1 1 0 0 1 0-2z"/>
+                                </svg>
+                                <div>
+                                    <strong>Module RTC deconnecte !</strong><br>
+                                    Verifiez la pile du module DS3231 et les cables I2C.
+                                </div>
+                            </div>`;
+                      } else {
                         const rtcDate = new Date(response.rtc_module_time + ' UTC');
                         const timeDiff = Math.abs(Math.round((browserDate - rtcDate) / 1000));