async loadCurrentUser(): Promise<IUser> {
    return new Promise<IUser>(ok => {
      this.getCurrentUser()
        .subscribe(
        next => {
          alert('функция, которую нужно ждать')
          this._currentUserSource.next(next);
          ok(next)
        },
        error => {
          this._currentUserSource.next(null);
          this._logService.addError(error);
          ok(null);
        })
    });
  }

await this._accountService.loadCurrentUser();
alert('функция компонента');

import { HttpClientModule, HTTP_INTERCEPTORS } from '@angular/common/http';
.....
@NgModule({
imports: [
    HttpClientModule,
.....
providers: [
    { provide: HTTP_INTERCEPTORS, useClass: AuthInterceptor, multi: true },

const routes: Routes = [
    { path: '', pathMatch: 'full', redirectTo: 'home' },
    { path: 'home', component: HomeComponent, canActivate: [AuthGuard] },
    { path: 'login', component: LoginComponent },
    { path: '', component: RegisterComponent },

    // если есть админская часть можно прикрыть ее отдельным гардианом
    { path: 'admin', component: AdminComponent, canActivate: [AdminAuthGuard] },

    { path: '**', redirectTo: 'home' }
];

import { BehaviorSubject } from 'rxjs';
public currentUser: BehaviorSubject<IUser> = new BehaviorSubject(null);

usSubscription: any;
constructor(private _us: UserService) {
    let user = this._us.currentUser.getValue(); // получаем текущего юзера
    this.usSubscription = this._us.currentUser.subscribe(
        user => consoler.log('user was changed:', user);
    ); // подписываемся на логин/логаут/изменение
}

login() {
    this.clearFormErrors();
    if (!this.loginForm.valid) {
        this.showFormErrors(['Заполните все поля']);
        return;
    }
    this._accountService.authorizationStatus()
        .then(ok => {
            if (ok) {
                this.RedirectToHome()
            }
            else {
                let formData = this.loginForm.value;
                let login: ILogin = {
                    userName: formData.username,
                    password: formData.password,
                    rememberMe: formData.rememberMe
                };
            }
            this._accountService.login(login).subscribe(
                result => {
                    if (!result.isSucceeded) {
                        this.showFormErrors(result.messages);
                        return;
                    } else {
                        this._accountService.loadCurrentUser()
                            .then(ok => this.RedirectToHome());
                    }
                },
                error => {
                    alert(<any>error);
                    return;
                }
            );
        })
        .catch(reason => alert(<any>reason));
}

errors: string[];

<div *ngIf="errors" class="formErrorLable red-text">
    <ng-template ngFor let-error [ngForOf]="errors">
        {{error}}<br />
    </ng-template>
</div>